Garmin Automobile Accessories 190 00307 00 User Manual

GPS 18  
TECHNICAL  
SPECIFICATIONS  
Garmin International, Inc.  
1200 E. 151st Street  
Olathe, KS 66062 USA  
190-00307-00, Revision D  
June 2005  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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© Copyright 2004–2005  
Garmin Ltd. or its subsidiaries  
All Rights Reserved  
Except as expressly provided below, no part of this manual may be reproduced, copied, transmitted,  
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written consent of Garmin. Garmin hereby grants permission to download a single copy of this  
manual and of any revision to this manual onto a hard drive or other electronic storage medium to be  
viewed and to print one copy of this manual or of any revision hereto, provided that such electronic or  
printed copy of this manual or revision must contain the complete text of this copyright notice and  
provided further that any unauthorized commercial distribution of this manual or any revision hereto  
is strictly prohibited.  
Information in this document is subject to change without notice. Garmin reserves the right to change  
or improve its products and to make changes in the content without obligation to notify any person or  
organization of such changes or improvements.  
Garmin International, Inc.  
1200 East 151st Street,  
Olathe, Kansas 66062, U.S.A.  
Tel. 913/397.8200 or 800/800.1020  
Fax 913/397.8282  
Garmin (Europe) Ltd.  
Unit 5, The Quadrangle, Abbey Park Industrial Estate,  
Romsey, SO51 9DL, U.K.  
Tel. 44/0870.8501241  
Fax 44/0870.8501251  
Garmin Corporation  
No. 68, Jangshu 2nd Road,  
Shijr, Taipei County, Taiwan  
Tel. 886/2.2642.9199  
Fax 886/2.2642.9099  
Web site address: www.garmin.com  
RECORD OF REVISIONS  
Revision Revision  
Date  
Description  
ECO #  
A
B
C
D
4/5/04  
Initial Release  
Revise to include PGRMO  
--  
6/7/04  
26125  
31279  
31511  
5/24/05 Add GPS 18 LVC-5m and GPS 18-5Hz  
6/6/05 Add 38400 baud to field 10 of PGRMC sentence  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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TABLE OF CONTENTS  
1 Introduction..................................................................................................................1  
1.1 Cautions ............................................................................................................................................1  
1.2 Limited Warranty..............................................................................................................................2  
1.3 Features.............................................................................................................................................3  
1.4 GPS 18 Series....................................................................................................................................4  
1.4.1  
1.4.2  
1.4.3  
GPS 18 USB...................................................................................................................................... 4  
GPS 18 PC ........................................................................................................................................ 4  
GPS 18 LVC, GPS 18 LVC-5m, and GPS 18-5Hz ........................................................................... 4  
1.5 Technical Specifications ...................................................................................................................5  
1.5.1  
Physical Characteristics..................................................................................................................... 5  
1.5.1.1 Size.................................................................................................................................... 5  
1.5.1.2 Weight............................................................................................................................... 5  
1.5.1.3 Color.................................................................................................................................. 5  
1.5.1.4 Case Material..................................................................................................................... 5  
1.5.1.5 Cable Length ..................................................................................................................... 5  
Electrical Characteristics................................................................................................................... 5  
1.5.2.1 Input Voltage..................................................................................................................... 5  
1.5.2.2 Input Current ..................................................................................................................... 5  
1.5.2.3 CMOS Serial Output Levels.............................................................................................. 5  
1.5.2.4 GPS Receiver Sensitivity .................................................................................................. 6  
Environmental Characteristics........................................................................................................... 6  
GPS Performance.............................................................................................................................. 6  
1.5.4.1 Receiver............................................................................................................................. 6  
1.5.4.2 Acquisition Times ............................................................................................................. 6  
1.5.4.3 Update Rate....................................................................................................................... 6  
1.5.4.4 Accuracy ........................................................................................................................... 6  
Interfaces........................................................................................................................................... 7  
1.5.5.1 GPS 18 Electrical Characteristics...................................................................................... 7  
1.5.5.2 Garmin Interface and Garmin USB Protocol..................................................................... 7  
1.5.5.3 GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz Protocols........................................................ 7  
1.5.5.4 Measurement Pulse Output (GPS 18 LVC & GPS 18-5Hz only)...................................... 7  
1.5.2  
1.5.3  
1.5.4  
1.5.5  
2 GPS 18 LVC & GPS 18-5Hz Wiring and Pinouts ....................................................8  
2.1 GPS 18 LVC & GPS 18-5Hz Pinout.................................................................................................8  
2.2 GPS 18 LVC & GPS 18-5Hz Wiring Diagrams ...............................................................................8  
3 Mechanical Characteristics & Mounting.................................................................10  
4 GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz Software Interface..............................12  
4.1 Received NMEA 0183 Sentences ...................................................................................................12  
4.1.1  
4.1.2  
4.1.3  
4.1.4  
4.1.5  
Almanac Information (ALM)...........................................................................................................12  
Sensor Initialization Information (PGRMI)......................................................................................13  
Sensor Configuration Information (PGRMC) ..................................................................................13  
Additional Sensor Configuration Information (PGRMC1) ..............................................................14  
Output Sentence Enable/Disable (PGRMO).....................................................................................14  
4.2 Transmitted NMEA 0183 Sentences...............................................................................................15  
4.2.1  
4.2.2  
4.2.3  
4.2.4  
4.2.5  
4.2.6  
4.2.7  
4.2.8  
Sentence Transmission Rate.............................................................................................................15  
Transmitted Time.............................................................................................................................16  
Global Positioning System Almanac Data (ALM)...........................................................................16  
Global Positioning System Fix Data (GGA) ....................................................................................17  
GPS DOP and Active Satellites (GSA) ............................................................................................17  
GPS Satellites in View (GSV)..........................................................................................................17  
Recommended Minimum Specific GPS/TRANSIT Data (RMC) ....................................................18  
Track Made Good and Ground Speed (VTG) ..................................................................................18  
GPS 18 Technical Specifications (190-00307-00)  
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4.2.9  
Geographic Position (GLL)..............................................................................................................18  
4.2.10 Estimated Error Information (PGRME) ...........................................................................................19  
4.2.11 GPS Fix Data Sentence (PGRMF) ...................................................................................................19  
4.2.12 Sensor Status Information (PGRMT)...............................................................................................19  
4.2.13 3D Velocity Information (PGRMV).................................................................................................19  
4.2.14 DGPS Beacon Information (PGRMB) .............................................................................................20  
4.3 Baud Rate Selection........................................................................................................................20  
4.4 Measurement Pulse Output (GPS 18 LVC & 18-5Hz only) ...........................................................20  
4.4.1  
4.4.2  
One-Pulse-Per-Second (PPS) Output (GPS 18 LVC Only)..............................................................20  
Five-Pulse-Per-Second Output (GPS 18-5Hz Only).........................................................................20  
Appendix A: Earth Datum List ......................................................................................21  
Appendix B: Binary Phase Output Format...................................................................24  
Appendix C: Changing the Baud Rate in Garmin Mode.............................................29  
Appendix D: GPS 18 PC/ LVC/18-5Hz & Windows Serial Mouse Issue ...................30  
Appendix E: Sensor Configuration Software................................................................32  
Downloading the Sensor Configuration Software............................................................................................32  
Selecting a Model.............................................................................................................................................32  
Connecting to the Sensor .................................................................................................................................32  
File Menu.........................................................................................................................................................33  
Comm Menu ....................................................................................................................................................33  
Config Menu....................................................................................................................................................33  
View Menu ......................................................................................................................................................34  
Help Menu .......................................................................................................................................................34  
LIST OF TABLES AND FIGURES  
Table 1: GPS 18 LVC & GPS 18-5Hz Wire Pinout....................................................................................... 8  
Figure 1: Computer Serial Port Interconnection............................................................................................. 8  
Figure 2. PDA Serial Port Interconnection..................................................................................................... 9  
Figure 3. Basic NMEA Device Interconnection............................................................................................. 9  
Figure 4a. GPS 18 Bottom Case Dimensions, Under Mold ......................................................................... 10  
Figure 4b. GPS 18 Bottom Case, Outside of Casing.................................................................................... 10  
Figure 5. GPS 18 Suction Cup Mount Center Hole Dimensions.................................................................. 11  
Figure 6. GPS 18 Flush Mount Dimensions................................................................................................. 11  
Figure 7. GPS 18 Flush Mount Center Hole Dimensions............................................................................. 11  
Table 2: NMEA 0183 Output Sentence Order and Size............................................................................... 15  
Table 3: Characters per Second for Available Baud Rates........................................................................... 15  
GPS 18 Technical Specifications (190-00307-00)  
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1
INTRODUCTION  
1.1 CAUTIONS  
CAUTION  
The GPS system is operated by the government of the United States, which is solely responsible for its  
accuracy and maintenance. Although the GPS 18 is a precision electronic NAVigation AID (NAVAID),  
any NAVAID can be misused or misinterpreted, and therefore become unsafe. Use these products at your  
own risk. To reduce the risk, carefully review and understand all aspects of these Technical Specifications  
before using the GPS 18. When in actual use, carefully compare indications from the GPS to all available  
navigation sources including the information from other NAVAIDs, visual sightings, charts, etc. For safety,  
always resolve any discrepancies before continuing navigation.  
FCC  
Compliance  
The GPS 18 complies with Part 15 of the FCC interference limits for Class B digital devices FOR HOME  
OR OFFICE USE. These limits are designed to provide reasonable protection against harmful interference  
in a residential installation, and are more stringent than “outdoor” requirements.  
Operation of this device is subject to the following conditions: (1) This device may not cause harmful  
interference, and (2) this device must accept any interference received, including interference that may  
cause undesired operation.  
This equipment generates, uses and can radiate radio frequency energy and, if not installed and used in  
accordance with the instructions, may cause harmful interference to radio communications. However, there  
is no guarantee that interference will not occur in a particular installation. If this equipment does cause  
harmful interference to radio or television reception, which can be determined by turning the equipment off  
and on, the user is encouraged to try to correct the interference by one or more of the following measures:  
Reorient or relocate the receiving antenna.  
Increase the separation between the equipment and receiver.  
Connect the equipment into an outlet on a circuit different from that to which the receiver is connected.  
Consult the dealer or an experienced radio/TV technician for help.  
The GPS 18 does not contain any user-serviceable parts. Unauthorized repairs or modifications could result  
in permanent damage to the equipment, and void your warranty and your authority to operate this device  
under Part 15 regulations.  
GPS 18 Technical Specifications (190-00307-00)  
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1.2 LIMITED WARRANTY  
This Garmin product is warranted to be free from defects in materials or workmanship for one year from  
the date of purchase. Within this period, Garmin will at its sole option, repair or replace any components  
that fail in normal use. Such repairs or replacement will be made at no charge to the customer for parts or  
labor, provided that the customer shall be responsible for any transportation cost. This warranty does not  
cover failures due to abuse, misuse, accident or unauthorized alteration or repairs.  
THE WARRANTIES AND REMEDIES CONTAINED HEREIN ARE EXCLUSIVE AND IN LIEU OF  
ALL OTHER WARRANTIES EXPRESS OR IMPLIED OR STATUTORY, INCLUDING ANY  
LIABILITY ARISING UNDER ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR A  
PARTICULAR PURPOSE, STATUTORY OR OTHERWISE. THIS WARRANTY GIVES YOU  
SPECIFIC LEGAL RIGHTS, WHICH MAY VARY FROM STATE TO STATE.  
IN NO EVENT SHALL GARMIN BE LIABLE FOR ANY INCIDENTAL, SPECIAL, INDIRECT OR  
CONSEQUENTIAL DAMAGES, WHETHER RESULTING FROM THE USE, MISUSE, OR  
INABILITY TO USE THIS PRODUCT OR FROM DEFECTS IN THE PRODUCT. Some states do not  
allow the exclusion of incidental or consequential damages, so the above limitations may not apply to you.  
Garmin retains the exclusive right to repair or replace the unit or software or offer a full refund of the  
purchase price at its sole discretion. SUCH REMEDY SHALL BE YOUR SOLE AND EXCLUSIVE  
REMEDY FOR ANY BREACH OF WARRANTY.  
To obtain warranty service, contact your local Garmin authorized dealer, or call Garmin Product Support at  
one of the numbers shown below for shipping instructions and an RMA tracking number. The unit should  
be securely packed with the tracking number clearly written on the outside of the package. The unit should  
then be sent, freight charges prepaid, to any Garmin warranty service station. A copy of the original sales  
receipt is required as the proof of purchase for warranty repairs.  
Garmin International, Inc.  
1200 East 151st Street,  
Olathe, Kansas 66062, U.S.A.  
Tel. 913/397.8200 or 800/800.1020  
Fax 913/397.8282  
Garmin (Europe) Ltd.  
Unit 5, The Quadrangle, Abbey Park Industrial Estate,  
Romsey, SO51 9DL, U.K.  
Tel. 44/0870.8501241  
Fax 44/0870.8501251  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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Overview  
The GPS 18 series products include an embedded receiver and an antenna. Based on the proven technology  
found in other Garmin 12-channel GPS receivers, the GPS 18 tracks up to 12 satellites at a time while  
providing fast time-to-first-fix, precise navigation updates (five times per second for the GPS 18-5Hz, and  
once per second for the GPS 18 USB, 18 PC, and 18 LVC), and low power consumption. This generation  
of GPS sensors adds the capability of FAA Wide Area Augmentation System (WAAS) differential GPS.  
The GPS 18’s far-reaching capability meets the sensitivity requirements of land navigation as well as the  
dynamics requirements of high-performance aircraft.  
The GPS 18 design uses the latest technology and high-level circuit integration to achieve superior  
performance while minimizing space and power requirements. All critical components of the system  
including the RF/IF receiver hardware and the digital baseband are designed and manufactured by Garmin  
to ensure the quality and capability of the GPS. The hardware capability combined with software  
intelligence makes the GPS 18 easy to integrate and use.  
The GPS 18 series products are designed to withstand rugged operating conditions and are waterproof to  
IEC 60529 IPX7, immersion in 1 meter of water for 30 minutes. These complete GPS receivers require  
minimal additional components to be supplied by an OEM or system integrator. A minimum system must  
provide the GPS with a source of power and a clear view of the GPS satellites. Internal FLASH memory  
allows the GPS to retain critical data such as satellite orbital parameters, last-known position, date and  
time. End user interfaces such as keyboards and displays are the responsibility of the application designer.  
1.3 FEATURES  
12-channel GPS receiver tracks and uses up to 12 satellites for fast, accurate positioning and low  
power consumption.  
Differential DGPS capability using real-time WAAS corrections yielding position errors of less than 3  
meters.  
Compact, rugged design ideal for applications with minimal space. Receiver position information can  
be displayed directly on a chartplotter or PC.  
User initialization is not required. Once installed, unit automatically produces navigation data after  
position fix is acquired.  
User-configurable navigation mode (2-dimensional or 3-dimensional fix).  
(GPS 18 LVC and GPS 18-5Hz only) Highly accurate measurement pulse output for precise timing  
measurements: one-pulse-per-second (1 Hz) for the GPS 18 LVC or 5 Hz for GPS 18-5Hz. Pulse width  
is configurable in 20 millisecond increments from 20 ms to 980 ms with 1 µs accuracy.  
Configurable for binary format carrier phase data output.  
FLASH-based program and non-volatile memory. New software revisions available through Web site  
download. Non-volatile memory does not require battery backup.  
Onboard rechargeable backup battery to maintain the real-time clock for up to 3 weeks.  
Configurable parameters include expected position, current time and date, preferred position fix type  
(2D, 3D, or automatic), and velocity filter time constant (none, automatic, or your choice between 2  
and 255 seconds).  
Waterproof design allows continuous exposure to the prevailing weather conditions at most locations.  
GPS 18 Technical Specifications (190-00307-00)  
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1.4 GPS 18 SERIES  
There are several different versions of GPS 18 available. Refer below for a list of the three major divisions  
of the GPS 18 Series.  
1.4.1 GPS 18 USB  
The GPS 18 USB interfaces to a computer with an available USB  
port. Drivers are available for use on Windows computers.  
Macintosh and Linux drivers are not available. After the drivers are  
loaded, the device appears to the Windows operating system as a  
USB-connected device and appears in Device Manager as a Garmin  
USB Device.  
1.4.2 GPS 18 PC  
The GPS 18 PC interfaces to a serial port of a computer via a DB-9  
connector and receives power through a 12-volt cigarette lighter  
adapter. The unit accepts TIA-232-F (RS-232) level inputs and  
transmits voltage levels that swing from zero V (ground) to 5 V  
TIA-232-F (RS-232) polarity.  
The GPS 18 PC can cause an issue with Windows operating systems  
if the DB9 connector is plugged into the computer before the  
navigation software is up and running. The Windows operating  
system may interpret the serial connector on the GPS 18 as a serial  
mouse. Please refer to Appendix D: GPS 18 PC/ LVC/18-5Hz &  
Windows Serial Mouse Issue for complete details.  
1.4.3 GPS 18 LVC, GPS 18 LVC-5m, and GPS 18-5Hz  
These products interface to a serial port. The units accept TIA-232-F (RS-232) level inputs and transmit  
voltage levels that swing from ground to the positive supply voltage, TIA-232-F (RS-232) polarity. They  
also have reverse polarity protection. The cable contains wires for power, ground, receive, transmit, and  
measurement pulse output.  
At the end of the cable, the wires are terminated in a connector that is  
used by Garmin for testing purposes. Most customers will remove this  
connector and replace it with another connector of their own choosing.  
Removing the factory installed connector and/or replacing with another  
customer-supplied connector will have no affect on the warranty (see  
Section 1.2 Limited Warranty). The factory-installed connector will mate  
with JST right-angle PCB-mount connector (model BM06B-SRSS-TBT)  
or side-entry PCB-mount connector (model SM06B-SRSS-TB). You may  
obtain technical information on these PCB-mount mating connectors  
from the JST Web site: http://www.jst.com/.  
Note: Unless otherwise specified, all references to the GPS 18 LVC also include the GPS 18 LVC-5m.  
GPS 18 Technical Specifications (190-00307-00)  
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1.5 TECHNICAL SPECIFICATIONS  
Specifications are subject to change without notice.  
1.5.1 Physical Characteristics  
1.5.1.1 Size  
61 mm in diameter and 19.5 mm in height  
1.5.1.2 Weight  
GPS 18 unit only (no cable): 1.9 oz (53.9 g)  
GPS 18 USB: 3.5 oz (100.4 g)  
GPS 18 PC: 6.5 oz (184.6 g)  
GPS 18 LVC (3 meter cable): 3.9 oz (110.6 g)  
GPS 18 LVC-5m (5 meter cable): 5.7 oz (161.6 g)  
GPS 18-5Hz (5 meter cable): 5.7 oz (161.6 g)  
1.5.1.3 Color  
Black  
1.5.1.4 Case Material  
Polycarbonate thermoplastic that is waterproof to IEC 60529 IPX7 level (immersion in 1 meter of water for  
30 minutes)  
1.5.1.5 Cable Length  
GPS 18 USB: 2 meter  
GPS 18 PC: 2 meter  
GPS 18 LVC: 3 meter (Garmin Part Number 010-00321-05)  
GPS 18 LVC-5m: 5 meter (Garmin Part Number 010-00321-06)  
GPS 18-5Hz: 5 meter  
1.5.2 Electrical Characteristics  
1.5.2.1 Input Voltage  
GPS 18 USB: 4.4–5.5 V  
GPS 18 PC: 8–30 V (Automotive supply from cigarette lighter jack)  
GPS 18 LVC: 4.0–5.5 V  
GPS 18-5Hz: 4.0–5.5 V  
1.5.2.2 Input Current  
GPS 18 USB: 55 mA @ 5.0 V  
GPS 18 PC: 50 mA @ 13.8 V  
GPS 18 LVC: 60 mA @ 5.0 V  
GPS 18-5Hz: 65 mA @ 5.0 V  
1.5.2.3 CMOS Serial Output Levels  
GPS 18 PC: 0 V to 5 V (Asynchronous Serial, TIA-232-F (RS-232) Compatible Polarity)  
GPS 18 LVC and GPS 18-5Hz: 0 V to Vin, between 4 and 5.5 V (Asynchronous Serial, TIA-232-F  
(RS-232) Compatible Polarity)  
GPS 18 Technical Specifications (190-00307-00)  
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1.5.2.4 GPS Receiver Sensitivity  
-165 dBW minimum  
1.5.3 Environmental Characteristics  
Operating Temperature: -30°C to +80°C  
Storage Temperature: -40°C to +90°C  
1.5.4 GPS Performance  
1.5.4.1 Receiver  
WAAS enabled; 12 parallel channel GPS receiver continuously tracks and uses up to 12 satellites (up to 11  
with Measurement Pulse Output active) to compute and update your position.  
1.5.4.2 Acquisition Times  
Reacquisition: Less than 2 seconds  
Warm:  
Cold:  
Approx. 15 seconds (all data known)  
Approx. 45 seconds (initial position, time, and almanac known; ephemeris unknown)  
AutoLocateTM: 5 minutes (almanac known; initial position and time unknown)  
SkySearch: 5 minutes (no data known)  
1.5.4.3 Update Rate  
GPS 18 USB, PC, and LVC: 1 record per second  
GPS 18-5Hz: 5 records per second  
1.5.4.4 Accuracy  
GPS Standard Positioning Service (SPS)  
Position: < 15 meters, 95% typical  
Velocity: 0.1 knot RMS steady state  
WAAS  
Position: < 3 meters, 95% typical  
Velocity: 0.1 knot RMS steady state  
Measurement Pulse Output Time: ±1 microsecond at rising edge of the pulse  
Dynamics: 999 knots velocity (only limited at altitude greater than 60,000 feet), 6g dynamics  
GPS 18 Technical Specifications (190-00307-00)  
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1.5.5 Interfaces  
1.5.5.1 GPS 18 Electrical Characteristics  
GPS 18 USB:  
USB 2.0 full-speed protocol compatible, as well as USB 1.1 full-speed protocol.  
GPS 18 PC and LVC: TIA-232-F (RS-232) compatible asynchronous receiver. Default setting is 4800  
baud.  
GPS 18-5Hz:  
TIA-232-F (RS-232) compatible asynchronous receiver. Default setting is 19200  
baud.  
1.5.5.2 Garmin Interface and Garmin USB Protocol  
Refer to the Garmin Device Interface Specification for information about the Garmin USB Protocol. The  
document is located on the Garmin Web site at: http://www.garmin.com/support/commProtocol.html. See  
also Appendix B: Binary Phase Output Format for additional information concerning access to raw pseudo-  
range and carrier phase data from the GPS 18 USB.  
Refer to the Garmin Device Interface Specification for details on the Garmin interface. At the time of this  
printing, these specs are available from the technical suppport section of our Web site:  
1.5.5.3 GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz Protocols  
NMEA 0183 Version 2.0 or NMEA 0183 Version 2.30 (Version 2.0 is factory default, programmable  
by data field 7 of the PGRMC1 sentence described in Section 4.1.4 Additional Sensor Configuration  
Information (PGRMC1).  
Available NMEA 0183 output sentences include GPALM, GPGGA, GPGSA, GPGSV, GPRMC,  
GPVTG, GPGLL, PGRME, PGRMF, PGRMT, PGRMV, and PGRMB (Garmin proprietary  
sentences). See Section 4.2 Transmitted NMEA 0183 Sentences for format descriptions.  
Configuration and initialization is accomplished with NMEA 0183 input sentences. Allows  
initialization of information such as expected position, date, time, earth datum, and differential mode.  
See Section 4.1 Received NMEA 0183 Sentences for format descriptions.  
Configurable for binary data output including GPS carrier phase data.  
1.5.5.4 Measurement Pulse Output (GPS 18 LVC & GPS 18-5Hz only)  
GPS 18 LVC: 1 Hz pulse with programmable width, configurable in 20 ms increments form 20 ms to  
980 ms. See Section 4.1.3 Sensor Configuration Information (PGRMC) for details about configuring  
the Measurement Pulse Output (or PPS) feature.  
GPS 18-5Hz: 5 Hz pulse synchronized with the time of fix. One of the five pulses will align with the  
UTC second boundary. The pulse width is programmable from 20 ms to 180 ms. The PGRMC  
sentence will indicate which pulse is at the top-of-the-second. See Section 4.1.3 Sensor Configuration  
Information (PGRMC) for details about configuring the Measurement Pulse Output (or PPS) feature.  
1 µs accuracy for all conditions in which the GPS 18 LVC or GPS 18-5Hz has reported a valid and  
accurate position fix for at least the previous 4 seconds.  
GPS 18 Technical Specifications (190-00307-00)  
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2
GPS 18 LVC & GPS 18-5Hz WIRING AND PINOUTS  
The GPS 18 LVC/18-5Hz interfaces to a serial port. The unit accepts TIA-232-F (RS-232) level inputs and  
transmits voltage levels from ground to the input voltage, TIA-232-F (RS-232) polarity.  
The GPS 18 LVC/18-5Hz wires are terminated with a six-wire connector that is used by Garmin for testing  
purposes. You can remove this connector without voiding your warranty (see Section 1.2 Limited  
Warranty).  
2.1 GPS 18 LVC & GPS 18-5Hz PINOUT  
GPS 18 Pin #  
Color  
Yellow  
Red  
Black  
White  
Black  
Green  
Signal Name  
Measurement Pulse Output  
Vin  
Wire Gauge  
1
2
3
4
5
6
28  
26  
28  
28  
26  
28  
Ground  
Transmit Data  
Ground  
Receive Data  
Table 1: GPS 18 LVC & GPS 18-5Hz Wire Pinout  
2.2 GPS 18 LVC & GPS 18-5Hz WIRING DIAGRAMS  
Figure 1: Computer Serial Port Interconnection  
GPS 18 Technical Specifications (190-00307-00)  
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Figure 2. PDA Serial Port Interconnection  
Figure 3. Basic NMEA Device Interconnection  
GPS 18 Technical Specifications (190-00307-00)  
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3
MECHANICAL CHARACTERISTICS & MOUNTING  
The central threaded recess accepts a metric M3 threaded bolt. The recess is approximately 4 mm deep  
(4.32 +/- 0.08 mm). The following drawings show example geometries for mounting hardware in case you  
wish to design your own custom mount. Figure 5 shows mounting geometry for a mount formed from steel  
sheet metal that is 1.15 mm thick. Figure 7 shows similar mounting geometry for mount formed from  
aluminum sheet metal that is 1.25 mm thick. Use caution when tightening the mounting bolt. Tightening  
the mounting bolt can cause the mount to pull tight directly against the metal insert, not against the plastic  
housing, which would tend to pull the insert out of the plastic. Figure 6 shows the dimensions of our GPS  
18 Flush Mount, part number 010-10453-00.  
Figure 4a. GPS 18 Bottom Case Dimensions, Under Mold  
Figure 4b. GPS 18 Bottom Case, Outside of Casing  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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Figure 5. GPS 18 Suction Cup Mount Center Hole Dimensions  
Figure 6. GPS 18 Flush Mount Dimensions  
Figure 7. GPS 18 Flush Mount Center Hole Dimensions  
GPS 18 Technical Specifications (190-00307-00)  
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4
GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz SOFTWARE INTERFACE  
The interface protocol design of the GPS 18 PC, LVC, and GPS 18-5Hz products is based on the National  
Marine Electronics Association’s NMEA 0183 ASCII interface specification. This standard is fully defined  
in NMEA 0183, Version 2.30. Copies may be obtained from NMEA, www.nmea.org.  
In addition to the standard NMEA 0183 sentences, the GPS 18 PC, LVC, and GPS 18-5Hz may also be  
configured to transmit information over their serial interface using NMEA 0183 compliant Garmin  
proprietary sentences. These proprietary sentences begin with the characters, “$PGRM”, instead of the  
characters “$G” that are typical of the standard NMEA 0183 sentences. The characters “$P” indicate that  
the sentence is a proprietary implementation and the characters and “GRM” indicate that it is Garmin’s  
proprietary sentence. The letter (or letters) that follow the characters “$PGRM” uniquely identifies that  
particular Garmin proprietary sentence.  
It is also possible to configure the GPS 18 PC, LVC, and GPS 18-5Hz to transmit binary phase data  
information over their serial interface. See Appendix B: Binary Phase Output Format for details.  
The GPS 18 USB does not transmit NMEA sentences: It transmits using the Garmin USB interface. The  
Garmin USB interface is discussed in the Garmin Device Interface Specification located on the Garmin  
Web site at: http://www.garmin.com/support/commProtocol.html. You can configure the GPS 18 USB to  
transmit binary phase data information over the USB interface. Refer to Appendix B: Binary Phase Output  
Format.  
The following sections describe the NMEA 0183 data format of each sentence transmitted and received by  
the GPS 18 PC, LVC, and GPS 18-5Hz products.  
4.1 RECEIVED NMEA 0183 SENTENCES  
The following paragraphs define the sentences that can be received on the GPS sensors’ port. Null fields in  
the configuration sentence indicate no change in the particular configuration parameter. All sentences  
received by the GPS sensor must be terminated with <CR><LF>, the ASCII characters for carriage return  
(0D hexadecimal) and line feed (0A hexadecimal). The checksum *hh is used for parity checking data and  
is not required, but is recommended for use in environments containing high electromagnetic noise. It is  
generally not required in normal PC environments. When used, the parity bytes (hh) are the ASCII  
representation of the exclusive-or (XOR) sum of all the characters between the “$” and “*” characters, non-  
inclusive. The hex representation must be a capital letter, such as 3D instead of 3d. Sentences may be  
truncated by <CR><LF> after any data field and valid fields up to that point will be acted on by the sensor.  
4.1.1 Almanac Information (ALM)  
The $GPALM sentence can be used to initialize the GPS sensor’s stored almanac information in the  
unlikely event of non-volatile memory loss or after storing longer than six months without tracking GPS  
satellites.  
$GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF>  
<1>  
<2>  
Total number of ALM sentences to be transmitted by the GPS sensor during almanac download.  
This field can be null or any number when sending almanac to the GPS sensor.  
Number of current ALM sentence. This field can be null or any number when sending almanac  
to the GPS sensor.  
<3>  
<4>  
<5>  
<6>  
<7>  
<8>  
<9>  
Satellite PRN number, 01 to 32  
GPS week number  
SV health, bits 17–24 of each almanac page  
Eccentricity  
Almanac reference time  
Inclination angle  
Rate of right ascension  
<10> Root of semi major axis  
<11> Omega, argument of perigee  
<12> Longitude of ascension node  
<13> Mean anomaly  
<14> af0 clock parameter  
<15> af1 clock parameter  
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4.1.2 Sensor Initialization Information (PGRMI)  
The $PGRMI sentence provides information used to initialize the GPS sensor’s set position and time used  
for satellite acquisition. Receipt of this sentence by the GPS sensor causes the software to restart the  
satellite acquisition process. If there are no errors in the sentence, it will be echoed upon receipt. If an error  
is detected, the echoed PGRMI sentence will contain the current default values. Current PGRMI defaults  
(with the exception of the Receiver Command, which is a command rather than a mode) can also be  
obtained by sending $PGRMIE to the GPS sensor.  
$PGRMI,<1>,<2>,<3>,<4>,<5>,<6>,<7>*hh<CR><LF>  
<1>  
Latitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-  
5Hz (leading zeros must be transmitted)  
<2>  
<3>  
Latitude hemisphere, N or S  
Longitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-  
5Hz (leading zeros must be transmitted)  
<4>  
<5>  
<6>  
<7>  
Longitude hemisphere, E or W  
Current UTC date, ddmmyy format  
Current UTC time, hhmmss format for GPS 18 PC/LVC; hhmmss.s format for GPS 18-5Hz  
Receiver Command, A = Auto Locate, R = Unit Reset  
4.1.3 Sensor Configuration Information (PGRMC)  
The $PGRMC sentence provides information used to configure the GPS sensor’s operation. Configuration  
parameters are stored in non-volatile memory and retained between power cycles. The GPS sensor will  
echo this sentence upon its receipt if no errors are detected. If an error is detected, the echoed PGRMC  
sentence will contain the current default values. Current default values can also be obtained by sending  
$PGRMCE to the GPS sensor.  
$PGRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>*hh<CR><LF>  
<1>  
Fix mode, A = automatic, 2 = 2D exclusively (host system must supply altitude),  
3 = 3D exclusively  
<2>  
<3>  
Altitude above/below mean sea level, -1500.0 to 18000.0 meters  
Earth datum index. If the user datum index (96) is specified, fields <4> through <8> must  
contain valid values. Otherwise, fields <4> through <8> must be null. Refer to Appendix A:  
Earth Datum List for a list of earth datum and the corresponding earth datum index.  
User earth datum semi-major axis, 6360000.000 to 6380000.000 meters (.001 meters  
resolution)  
User earth datum inverse flattening factor, 285.0 to 310.0 (10-9 resolution)  
User earth datum delta x earth centered coordinate, -5000.0 to 5000.0 meters (1 meter  
resolution)  
<4>  
<5>  
<6>  
<7>  
<8>  
<9>  
User earth datum delta y earth centered coordinate, -5000.0 to 5000.0 meters (1 meter  
resolution)  
User earth datum delta z earth centered coordinate, -5000.0 to 5000.0 meters (1 meter  
resolution)  
Differential mode, A = automatic (output DGPS data when available, non-DGPS otherwise), D  
= differential exclusively (output only differential fixes)  
<10> NMEA 0183 Baud rate, 1 = 1200, 2 = 2400, 3 = 4800, 4 = 9600, 5 = 19200, 6 = 300, 7 = 600,  
8 = 38400 (for GPS 18-5Hz only)  
<11> Velocity filter, 0 = No filter, 1 = Automatic filter, 2–255 = Filter time constant  
(for example, 10 = 10 second filter)  
<12> Measurement Pulse Output, 1 = Disabled, 2 = Enabled  
<13> Measurement Pulse Output pulse length, (n+1)*20 ms  
For 18 LVC/PC n = 0 through 48 (max. 980 ms)  
For GPS 18-5Hz n = 0 through 8 (max. 180 ms)  
Example: n = 4 corresponds to a 100 ms wide pulse  
<14> Dead reckoning valid time 1 to 30 sec. for the GPS 18 PC/LVC  
or 0.2 to 30.0 sec. for the GPS 18-5Hz  
All configuration changes take effect after receipt of a valid value except baud rate and Measurement Pulse  
Output mode. Baud rate and Measurement Pulse Output mode changes take effect on the next power cycle  
or an external reset event.  
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4.1.4 Additional Sensor Configuration Information (PGRMC1)  
The $PGRMC1 sentence provides additional information used to configure the GPS sensor operation.  
Configuration parameters are stored in non-volatile memory and retained between power cycles. The GPS  
sensor will echo this sentence upon its receipt if no errors are detected. If an error is detected, the echoed  
PGRMC1 sentence will contain the current default values. Current default values can also be obtained by  
sending $PGRMC1E to the GPS sensor.  
$PGRMC1,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>*hh<CR><LF>  
<1>  
NMEA 0183 output time 1 to 900 (sec). Not applicable to GPS 18-5Hz, which always outputs  
data at 5 Hz (200 ms)  
<2>  
<3>  
<4>  
<5>  
<6>  
<7>  
<8>  
<9>  
Binary Phase Output Data, 1 = Off, 2 = On.  
Automatic Position Averaging when Stopped, 1 = Off, 2 = On  
No Effect (DGPS beacon frequency: 0.0, 283.5 to 325.0 kHz in 0.5 kHz steps)  
No Effect (DGPS beacon bit rate: 0, 25, 50, 100, or 200 bps)  
No Effect (DGPS beacon scanning, 1 = Off, 2 = On)  
NMEA 0183 version 2.30 mode indicator, 1 = Off, 2 = On  
DGPS WAAS mode, W = WAAS Enabled, N = WAAS Disabled  
Power Save Mode, P = Power Save mode, N = Normal  
<10> Adaptive Transmission Enabled, 1 = Off, 2 = On  
<11> Auto Power Off, 1 = Off, 2 = On  
<12> Power On with External Charger, 1 = Off, 2 = On  
<13> Measurement Pulse Output Auto Off Mode, 1 = Off, 2 = On  
Configuration changes take effect immediately, with the exception of Binary Phase Output Data, which  
takes effect on the next power cycle or a reset event. Send the sentence “$PGRMI,,,,,,,R” to command a  
reset (refer to Section 4.1.2 Sensor Initialization Information (PGRMI)). If the GPS sensor is in the Binary  
data mode, it is necessary to send the following eight-byte data stream to temporarily change the data  
format to NMEA 0183. Then follow by sending a PGRMC1 sentence that turns off the Binary Phase  
Output Data format:  
10 0A 02 26 00 CE 10 03 (Hexadecimal)  
4.1.5 Output Sentence Enable/Disable (PGRMO)  
The $PGRMO sentence provides the ability to enable and disable specific output sentences. The following  
sentences are enabled at the factory for the GPS 18 PC and LVC: GPGGA, GPGSA, GPGSV, GPRMC,  
and PGRMT.  
The following sentences are enabled at the factory for the GPS 18-5Hz: GPGGA, GPGSA, GPRMC,  
GPUTG, and PGRMT.  
$PGRMO,<1>,<2>*hh<CR><LF>  
<1>  
<2>  
Target sentence description (for example, PGRMT, GPGSV, etc.)  
Target sentence mode, where 0 = disable specified sentence, 1 = enable specified sentence, 2 =  
disable all output sentences, 3 = enable all output sentences (except GPALM), 4 = restore  
factory default output sentences  
The following notes apply to the PGRMO input sentence:  
1. If the target sentence mode is ‘2’ (disable all), ‘3’ (enable all), or ‘4’ (restore defaults), the target  
sentence description is not checked for validity. In this case, an empty field is allowed (for example,  
$PGRMO,,3), or the mode field may contain from 1 to 5 characters.  
2. If the target sentence mode is ‘0’ (disable) or ‘1’ (enable), the target sentence description field must be  
an identifier for one of the sentences that can be output by the GPS sensor.  
3. If either the target sentence mode field or the target sentence description field is not valid, the PGRMO  
sentence will have no effect.  
4. $PGRMO,GPALM,1 will cause the GPS sensor to transmit all stored almanac information. All other  
NMEA 0183 sentence transmission will be suspended temporarily.  
5. $PGRMO,,G will cause the COM port to change to Garmin Data Transfer format for the duration of  
the power cycle. The Garmin mode is required for GPS 18 series product software updates.  
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4.2 TRANSMITTED NMEA 0183 SENTENCES  
The subsequent paragraphs define the sentences that can be transmitted by the GPS 18 PC and LVC.  
4.2.1 Sentence Transmission Rate  
Sentences are transmitted with respect to the user selected baud rate.  
The GPS sensor will transmit each sentence (except where noted in particular transmitted sentence  
descriptions) at a periodic rate based on the user selected baud rate and user selected output sentences. The  
GPS sensor will transmit the selected sentences contiguously. The length of the transmission can be  
determined by the following equation and Tables 2 and 3:  
total characters to be transmitted  
length of transmission  
=
---------------------------------------------  
characters transmitted per second  
Sentence  
GPRMC  
GPGGA  
GPGSA  
GPGSV  
PGRME  
GPGLL  
GPVTG  
PGRMV  
PGRMF  
PGRMB  
PGRMT  
Output by Default?  
Maximum Characters  
74  
82  
66  
70  
35  
44  
42  
32  
82  
40  
50  
(PC and LVC only)  
(PC and LVC only)  
(18-5Hz only)  
(PC and LVC only)  
Once per minute  
Table 2: NMEA 0183 Output Sentence Order and Size  
Baud  
300  
600  
Characters per Second  
30  
60  
1200  
2400  
4800  
9600  
19200  
38400  
120  
240  
480  
960  
1920  
3840  
Table 3: Characters per Second for Available Baud Rates  
The maximum number of fields allowed in a single sentence is 82 characters including delimiters. Values  
in the table include the sentence start delimiter character “$” and the termination delimiter <CR><LF>. For  
the GPS 18 PC and LVC, the factory set defaults result in a once per second transmission at the NMEA  
0183 specification transmission rate of 4800 baud. For the GPS 18-5Hz, the factory set defaults will result  
in a five times per second transmission at 19200 baud.  
For the GPS 18 LVC: Regardless of the selected baud rate, the information transmitted by the GPS sensor  
is referenced to the one-pulse-per-second output pulse immediately preceding the GPRMC sentence, or  
whichever sentence is output first in the burst (see Table 2 above).  
For the GPS 18-5Hz: Regardless of the selected baud rate, the information transmitted by the GPS sensor is  
referenced to the preceding five times per second output pulse.  
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4.2.2 Transmitted Time  
The GPS sensor outputs UTC (Coordinated Universal Time) date and time of day in the transmitted  
sentences. Before the initial position fix, the on-board clock provides the date and time of day. After the  
initial position fix, the date and time of day are calculated using GPS satellite information and are  
synchronized with the measurement pulse output.  
The GPS 18-5Hz outputs a UTC with a tenths-of-a-second precision: 123456.8, for example.  
The GPS sensor uses information obtained from the GPS satellites to add or delete UTC leap seconds and  
correct the transmitted date and time of day. The transmitted date and time of day for leap second  
correction follow the guidelines in “National Institute of Standards and Technology Special Publication  
432 (Revised 1990)” (for sale by the Superintendent of Documents, U.S. Government Printing Office,  
Washington, D.C., 20402, U.S.A.).  
When a positive leap second is required, one second is inserted at the beginning of the first hour (0h 0m 0s)  
of the day that the positive leap is occurring. The minute containing the leap second is 61 seconds long. The  
GPS sensor would have transmitted this information for the leap second added December 31, 1998 as  
follows:  
$GPRMC,235959,A,3851.3651,N,09447.9382,W,000.0,221.9,071103,003.3,E*69  
$GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67  
$GPRMC,000000,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*67  
$GPRMC,000001,A,3851.3651,N,09447.9382,W,000.0,221.9,081103,003.3,E*66  
If a negative leap second should be required, one second will be deleted at the end of some UTC month.  
The minute containing the leap second will be only 59 seconds long. In this case, the GPS sensor will not  
transmit the time of day 0h 0m 0s (the “zero” second) for the day from which the leap second is removed.  
$GPRMC,235959,A,3851.3650,N,09447.9373,W,000.0,000.0,111103,003.3,E*69  
$GPRMC,000001,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*6A  
$GPRMC,000002,A,3851.3650,N,09447.9373,W,000.0,000.0,121103,003.3,E*69  
4.2.3 Global Positioning System Almanac Data (ALM)  
Almanac sentences are not normally transmitted. Send the GPS sensor a $PGRMO,GPALM,1 command to  
initiate almanac transmission. Upon receipt of this command, the GPS sensor will transmit available  
almanac information on GPALM sentences. During the transmission of almanac sentences, other NMEA  
0183 data output is suspended temporarily.  
$GPALM,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF>  
<field information> can be found in Section 4.1.1 Almanac Information (ALM).  
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4.2.4 Global Positioning System Fix Data (GGA)  
$GPGGA,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,M,<10>,M,<11>,<12>*hh<CR><LF>  
<1>  
<2>  
UTC time of position fix, hhmmss format for GPS 18 PC or LVC; hhmmss.s format for GPS 18-  
5Hz  
Latitude, ddmm.mmmm format for GPS 18 PC/LVC; ddmm.mmmmm for GPS 18-5Hz  
(leading zeros will be transmitted)  
<3>  
<4>  
Latitude hemisphere, N or S  
Longitude, dddmm.mmmm format for GPS 18 PC/LVC; dddmm.mmmmm for GPS 18-5Hz  
(leading zeros will be transmitted)  
<5>  
<6>  
Longitude hemisphere, E or W  
GPS quality indication, 0 = fix not available, 1 = Non-differential GPS fix available, 2 =  
Differential GPS (WAAS) fix available, 6 = Estimated  
Number of satellites in use, 00 to 12 (leading zeros will be transmitted)  
Horizontal dilution of precision, 0.5 to 99.9  
<7>  
<8>  
<9>  
Antenna height above/below mean sea level, -9999.9 to 99999.9 meters  
<10> Geoidal height, -999.9 to 9999.9 meters  
<11> Null (Differential GPS  
<12> Null (Differential Reference Station ID)  
4.2.5 GPS DOP and Active Satellites (GSA)  
$GPGSA,<1>,<2>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<3>,<4>,<5>,<6>*hh<CR><LF>  
<1>  
<2>  
<3>  
Mode, M = manual, A = automatic  
Fix type, 1 = not available, 2 = 2D, 3 = 3D  
PRN number, 01 to 32, of satellite used in solution, up to 12 transmitted (leading zeros will be  
transmitted)  
<4>  
<5>  
<6>  
Position dilution of precision, 0.5 to 99.9  
Horizontal dilution of precision, 0.5 to 99.9  
Vertical dilution of precision, 0.5 to 99.9  
4.2.6 GPS Satellites in View (GSV)  
$GPGSV,<1>,<2>,<3>,<4>,<5>,<6>,<7>,...<4>,<5>,<6>,<7>*hh<CR><LF>  
<1>  
<2>  
<3>  
<4>  
<5>  
<6>  
<7>  
Total number of GSV sentences to be transmitted  
Number of current GSV sentence  
Total number of satellites in view, 00 to 12 (leading zeros will be transmitted)  
Satellite PRN number, 01 to 32 (leading zeros will be transmitted)  
Satellite elevation, 00 to 90 degrees (leading zeros will be transmitted)  
Satellite azimuth, 000 to 359 degrees, true (leading zeros will be transmitted)  
Signal to noise ratio (C/No) 00 to 99 dB, null when not tracking (leading zeros will be  
transmitted)  
NOTE: Items <4>,<5>,<6>, and <7> repeat for each satellite in view to a maximum of four (4) satellites  
per sentence. Additional satellites in view information must be sent in subsequent bursts of NMEA 0183  
data. These fields will be null if unused.  
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4.2.7 Recommended Minimum Specific GPS/TRANSIT Data (RMC)  
$GPRMC,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>*hh<CR><LF>  
<1>  
UTC time of position fix, hhmmss format for GPS 18 PC/LVC;  
hhmmss.s format for GPS 18-5Hz  
<2>  
<3>  
Status, A = Valid position, V = NAV receiver warning  
Latitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<4>  
<5>  
Latitude hemisphere, N or S  
Longitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<6>  
<7>  
Longitude hemisphere, E or W  
Speed over ground, GPS 18 PC and LVC: 000.0 to 999.9 knots, GPS 18-5Hz: 000.00 to 999.99  
knots (leading zeros will be transmitted)  
<8>  
<9>  
Course over ground, 000.0 to 359.9 degrees, true (leading zeros will be transmitted)  
UTC date of position fix, ddmmyy format  
<10> Magnetic variation, 000.0 to 180.0 degrees (leading zeros will be transmitted)  
<11> Magnetic variation direction, E or W (westerly variation adds to true course)  
<12> Mode indicator (only output if NMEA 0183 version 2.30 active), A = Autonomous,  
D = Differential, E = Estimated, N = Data not valid  
4.2.8 Track Made Good and Ground Speed (VTG)  
$GPVTG,<1>,T,<2>,M,<3>,N,<4>,K,<5>*hh<CR><LF>  
<1>  
<2>  
<3>  
<4>  
<5>  
True course over ground, GPS 18 PC and LVC: 000 to 359 degrees, GPS 18-5Hz: 000.0 to  
359.0 degrees(leading zeros will be transmitted)  
Magnetic course over ground, 000 to 359 degrees, GPS 18-5Hz: 000.0 to 359.0 degrees(leading  
zeros will be transmitted)  
Speed over ground, GPS 18 PC and LVC: 000.0 to 999.9 knots, GPS 18-5Hz: 000.00 to 999.99  
knots (leading zeros will be transmitted)  
Speed over ground, GPS 18 PC and LVC: 0000.0 to 1851.8 kilometers per hour, GPS 18-5Hz:  
0000.00 to 1851.89 (leading zeros will be transmitted)  
Mode indicator (only output if NMEA 0183 version 2.30 active), A = Autonomous,  
D = Differential, E = Estimated, N = Data not valid  
4.2.9 Geographic Position (GLL)  
$GPGLL,<1>,<2>,<3>,<4>,<5>,<6>,<7>*hh<CR><LF>  
<1>  
Latitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<2>  
<3>  
Latitude hemisphere, N or S  
Longitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<4>  
<5>  
Longitude hemisphere, E or W  
UTC time of position fix, hhmmss format for GPS 18 PC/LVC; hhmmss.s format for GPS 18-  
5Hz  
<6>  
<7>  
Status, A = Valid position, V = NAV receiver warning  
Mode indicator (only output if NMEA 0183 version 2.30 active), A = Autonomous,  
D = Differential (WAAS), E = Estimated, N = Data not valid  
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4.2.10 Estimated Error Information (PGRME)  
$PGRME,<1>,M,<2>,M,<3>,M*hh<CR><LF>  
<1>  
<2>  
<3>  
Estimated horizontal position error (HPE), 0.0 to 999.9 meters  
Estimated vertical position error (VPE), 0.0 to 999.9 meters  
Estimated position error (EPE), 0.0 to 999.9 meters  
4.2.11 GPS Fix Data Sentence (PGRMF)  
$PGRMF,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>,<10>,<11>,<12>,<13>,<14>,<15>*hh<CR><LF>  
<1>  
<2>  
<3>  
<4>  
GPS week number (0 to 1023)  
GPS seconds (0 to 604799)  
UTC date of position fix, ddmmyy format  
UTC time of position fix, hhmmss format for GPS 18 PC/LVC; hhmmss.s format for GPS 18-  
5Hz  
<5>  
<6>  
GPS leap second count  
Latitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<7>  
<8>  
Latitude hemisphere, N or S  
Longitude, ddmm.mmm format for GPS 18 PC/LVC; ddmm.mmmmm format for GPS 18-5Hz  
(leading zeros must be transmitted)  
<9>  
Longitude hemisphere, E or W  
<10> Mode, M = manual, A = automatic  
<11> Fix type, 0 = no fix, 1 = 2D fix, 2 = 3D fix  
<12> Speed over ground, 0 to 1851 kilometers/hour  
<13> Course over ground, 0 to 359 degrees, true  
<14> Position dilution of precision, 0 to 9 (rounded to nearest integer value)  
<15> Time dilution of precision, 0 to 9 (rounded to nearest integer value)  
4.2.12 Sensor Status Information (PGRMT)  
The Garmin Proprietary sentence $PGRMT gives information concerning the status of the GPS sensor.  
This sentence is transmitted once per minute regardless of the selected baud rate.  
$PGRMT,<1>,<2>,<3>,<4>,<5>,<6>,<7>,<8>,<9>*hh<CR><LF>  
<1>  
<2>  
<3>  
<4>  
<5>  
<6>  
<7>  
<8>  
<9>  
Product, model and software version (variable length field, for example, “GPS 18 VER 2.05”)  
ROM checksum test, P = pass, F = fail  
Receiver failure discrete, P = pass, F = fail  
Stored data lost, R = retained, L = lost  
Real time clock lost, R = retained, L = lost  
Oscillator drift discrete, P = pass, F = excessive drift detected  
Data collection discrete, C = collecting, null if not collecting  
GPS sensor temperature in degrees C  
GPS sensor configuration data, R = retained, L = lost  
4.2.13 3D Velocity Information (PGRMV)  
$PGRMV,<1>,<2>,<3>*hh<CR><LF>  
<1>  
<2>  
<3>  
True east velocity, -514.4 to 514.4 meters/second for GPS 18 PC/LVC; -514.44 to 514.44 for  
GPS 18-5Hz  
True north velocity, -514.4 to 514.4 meters/second for GPS 18 PC/LVC; -514.44 to 514.44 for  
GPS 18-5Hz  
Up velocity, -999.9 to 999.9 meters/second for GPS 18 PC/LVC; -999.99 to 999.99 for GPS 18-  
5Hz  
GPS 18 Technical Specifications (190-00307-00)  
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4.2.14 DGPS Beacon Information (PGRMB)  
NOTE: The GPS 18 products do not support PGRMB at this time.  
$PGRMB,<1>,<2>,<3>,<4>,<5>,K,<6>,<7>,<8>*hh<CR><LF>  
<1>  
<2>  
<3>  
<4>  
<5>  
<6>  
Beacon tune frequency, 0.0, 283.5 to 325.0 kHz in 0.5 kHz steps  
Beacon bit rate, 0, 25, 50, 100, or 200 bps  
Beacon SNR, 0 to 31  
Beacon data quality, 0 to 100  
Distance to beacon reference station in kilometers  
Beacon receiver communication status (0 = Check Wiring, 1 = No Signal, 2 = Tuning, 3 =  
Receiving, 4= Scanning)  
<7>  
<8>  
DGPS fix source (R = RTCM, W = WAAS, N = Non-DGPS Fix)  
DGPS mode, A = Automatic, W = WAAS Only, R = RTCM Only, N = None (DGPS disabled)  
4.3 BAUD RATE SELECTION  
Baud rate selection can be performed by sending the appropriate configuration sentence to the GPS sensor  
as described in the $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <10>.  
4.4 MEASUREMENT PULSE OUTPUT (GPS 18 LVC & 18-5Hz ONLY)  
4.4.1 One-Pulse-Per-Second (PPS) Output (GPS 18 LVC Only)  
The highly accurate one-pulse-per-second (PPS) output is provided for applications requiring precise  
timing measurements. After the initial position fix has been calculated, the PPS signal is generated and  
continues until power down. The rising edge of the signal is aligned to the start of each GPS second within  
1 µs for all conditions in which the receiver has reported a valid and accurate position for at least the  
previous 4 seconds.  
The NMEA 0183 sentences that follow each rising edge of the PPS signal tell when you were and where  
you were at that previous rising edge of the PPS signal, beginning with the GPRMC sentence as the lead  
sentence in any particular NMEA 0183 record.  
Regardless of the selected baud rate, the information transmitted by the GPS 18 series products is  
referenced to the pulse immediately preceding the NMEA 0183 RMC sentence.  
The accuracy of the one-pulse-per-second output is maintained only while the GPS receiver is computing a  
valid position fix. To obtain the most accurate results, the one-pulse-per-second output should be calibrated  
against a local time reference to compensate for cable and internal receiver delays and the local time bias.  
The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms  
and 980 ms as described in $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <13>.  
4.4.2 Five-Pulse-Per-Second Output (GPS 18-5Hz Only)  
The highly accurate five-pulse-per-second output is provided for applications requiring precise timing  
measurements. After the initial position fix has been calculated, the GPS 18-5Hz generates the pulse signal,  
which continues until power down. The rising edge of the signal is aligned to the start of each GPS second  
within 1 µs for all conditions in which the receiver has reported a valid and accurate position for at least the  
previous 4 seconds.  
The NMEA 0183 sentences that follow each rising edge of the Measurement Pulse Output signal tell when  
and where you were at that previous rising edge of the Measurement Pulse Output signal, beginning with  
the GPRMC sentence as the lead sentence in any particular NMEA 0183 record.  
Regardless of the selected baud rate, the information transmitted by the GPS 18-5Hz is referenced to the  
preceding five times per-second output pulse.  
The accuracy of the five-pulse-per-second output is maintained only while the GPS 18-5Hz can compute a  
valid position fix. To obtain the most accurate results, the five-pulse-per-second output should be calibrated  
against a local time reference to compensate for cable and internal receiver delays and the local time bias.  
GPS 18 Technical Specifications (190-00307-00)  
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The default pulse width is 100 ms, however; it may be programmed in 20 ms increments between 20 ms  
and 180 ms as described in $PGRMC Section 4.1.2 Sensor Initialization Information (PGRMI), field <13>.  
APPENDIX A: EARTH DATUM LIST  
The following is a list of the Garmin GPS 18 Earth datum indices and the corresponding earth datum name  
(including the area of application):  
0
ADINDAN–Ethiopia, Mali, Senegal, Sudan  
AFGOOYE–Somalia  
1
2
AIN EL ABD 1970–Bahrain Island, Saudi Arabia  
ANNA 1 ASTRO 1965–Cocos Island  
3
4
ARC 1950–Botswana, Lesotho, Malawi, Swaziland, Zaire, Zambia, Zimbabwe  
ARC 1960–Kenya, Tanzania  
5
6
ASCENSION ISLAND 1958–Ascension Island  
ASTRO BEACON “E”–Iwo Jima Island  
AUSTRALIAN GEODETIC 1966–Australia, Tasmania Island  
AUSTRALIAN GEODETIC 1984–Australia, Tasmania Island  
ASTRO DOS 71/4–St. Helena Island  
7
8
9
10  
11  
12  
13  
14  
15  
16  
17  
18  
19  
20  
21  
22  
23  
24  
25  
26  
27  
ASTRONOMIC STATION 1952–Marcus Island  
ASTRO B4 SOROL ATOLL–Tern Island  
BELLEVUE (IGN)–Efate and Erromango Islands  
BERMUDA 1957–Bermuda Islands  
BOGOTA OBSERVATORY–Colombia  
CAMPO INCHAUSPE–Argentina  
CANTON ASTRO 1966–Phoenix Islands  
CAPE CANAVERAL–Florida, Bahama Islands  
CAPE–South Africa  
CARTHAGE–Tunisia  
CHATHAM 1971–Chatham Island (New Zealand)  
CHUA ASTRO–Paraguay  
CORREGO ALEGRE–Brazil  
DJAKARTA (BATAVIA)–Sumatra Island (Indonesia)  
DOS 1968–Gizo Island (New Georgia Islands)  
EASTER ISLAND 1967–Easter Island  
EUROPEAN 1950–Austria, Belgium, Denmark, Finland, France, Germany, Gibraltar, Greece,  
Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland  
28  
29  
30  
31  
32  
EUROPEAN 1979–Austria, Finland, Netherlands, Norway, Spain, Sweden, Switzerland  
FINLAND HAYFORD 1910–Finland  
GANDAJIKA BASE–Republic of Maldives  
GEODETIC DATUM 1949–New Zealand  
ORDNANCE SURVEY OF GREAT BRITAIN 1936–England, Isle of Man, Scotland, Shetland  
Islands, Wales  
33  
GUAM 1963–Guam Island  
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34  
35  
36  
37  
38  
39  
40  
41  
42  
43  
44  
45  
46  
47  
48  
49  
50  
51  
52  
53  
54  
55  
56  
57  
GUX 1 ASTRO–Guadalcanal Island  
HJORSEY 1955–Iceland  
HONG KONG 1963–Hong Kong  
INDIAN–Bangladesh, India, Nepal  
INDIAN–Thailand, Vietnam  
IRELAND 1965–Ireland  
ISTS O73 ASTRO 1969–Diego Garcia  
JOHNSTON ISLAND 1961–Johnston Island  
KANDAWALA–Sri Lanka  
KERGUELEN ISLAND–Kerguelen Island  
KERTAU 1948–West Malaysia, Singapore  
L.C. 5 ASTRO–Cayman Brac Island  
LIBERIA 1964–Liberia  
LUZON–Mindanao Island  
LUZON–Phillippines (excluding Mindanao Island)  
MAHE 1971–Mahe Island  
MARCO ASTRO–Salvage Islands  
MASSAWA–Eritrea (Ethiopia)  
MERCHICH–Morocco  
MIDWAY ASTRO 1961–Midway Island  
MINNA–Nigeria  
NORTH AMERICAN 1927–Alaska  
NORTH AMERICAN 1927–Bahamas (excluding San Salvador Island)  
NORTH AMERICAN 1927–Central America (Belize, Costa Rica, El Salvador, Guatemala,  
Honduras, Nicaragua)  
58  
59  
60  
NORTH AMERICAN 1927–Canal Zone  
NORTH AMERICAN 1927–Canada (including Newfoundland Island)  
NORTH AMERICAN 1927–Caribbean (Barbados, Caicos Islands, Cuba, Dominican Republic,  
Grand Cayman, Jamaica, Leeward Islands, Turks Islands)  
61  
62  
63  
64  
65  
66  
67  
68  
69  
70  
71  
72  
NORTH AMERICAN 1927–Mean Value (CONUS)  
NORTH AMERICAN 1927–Cuba  
NORTH AMERICAN 1927–Greenland (Hayes Peninsula)  
NORTH AMERICAN 1927–Mexico  
NORTH AMERICAN 1927–San Salvador Island  
NORTH AMERICAN 1983–Alaska, Canada, Central America, CONUS, Mexico  
NAPARIMA, BWI–Trinidad and Tobago  
NAHRWAN–Masirah Island (Oman)  
NAHRWAN–Saudi Arabia  
NAHRWAN–United Arab Emirates  
OBSERVATORIO 1966–Corvo and Flores Islands (Azores)  
OLD EGYPTIAN–Egypt  
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73  
74  
75  
76  
77  
78  
79  
80  
81  
82  
83  
OLD HAWAIIAN–Mean Value  
OMAN–Oman  
PICO DE LAS NIEVES–Canary Islands  
PITCAIRN ASTRO 1967–Pitcairn Island  
PUERTO RICO–Puerto Rico, Virgin Islands  
QATAR NATIONAL–Qatar  
QORNOQ–South Greenland  
REUNION–Mascarene Island  
ROME 1940–Sardinia Island  
RT 90–Sweden  
PROVISIONAL SOUTH AMERICAN 1956–Bolivia, Chile, Colombia, Ecuador, Guyana,  
Peru, Venezuela  
84  
SOUTH AMERICAN 1969–Argentina, Bolivia, Brazil, Chile, Colombia, Ecuador, Guyana,  
Paraguay, Peru, Venezuela, Trinidad and Tobago  
85  
SOUTH ASIA–Singapore  
86  
PROVISIONAL SOUTH CHILEAN 1963–South Chile  
SANTO (DOS)–Espirito Santo Island  
SAO BRAZ–Sao Miguel, Santa Maria Islands (Azores)  
SAPPER HILL 1943–East Falkland Island  
SCHWARZECK–Namibia  
87  
88  
89  
90  
91  
SOUTHEAST BASE–Porto Santo and Madeira Islands  
SOUTHWEST BASE–Faial, Graciosa, Pico, Sao Jorge, and Terceira Islands (Azores)  
TIMBALAI 1948–Brunei and East Malaysia (Sarawak and Sabah)  
TOKYO–Japan, Korea, Okinawa  
TRISTAN ASTRO 1968–Tristan da Cunha  
User defined earth datum  
92  
93  
94  
95  
96  
97  
VITI LEVU 1916–Viti Levu Island (Fiji Islands)  
WAKE-ENIWETOK 1960–Marshall Islands  
WORLD GEODETIC SYSTEM 1972  
WORLD GEODETIC SYSTEM 1984  
ZANDERIJ–Surinam  
98  
99  
100  
101  
102  
103  
104  
105  
106  
107  
108  
109  
CH-1903–Switzerland  
Hu-Tzu-Shan  
Indonesia 74  
Austria  
Potsdam  
Taiwan–modified Hu-Tzu-Shan  
GDA–Geocentric Datum of Australia  
Dutch  
GPS 18 Technical Specifications (190-00307-00)  
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APPENDIX B: BINARY PHASE OUTPUT FORMAT  
In binary phase output mode, GPS 18 series products will transmit two types of packets once per second.  
One record contains primarily post-process information such as position and velocity information. The  
second record contains receiver measurement information. For the GPS 18 PC, GPS 18 LVC, and GPS 18-  
5Hz, the records are sent at a default baud rate of 9600 baud, 8 data bits, and no parity.  
To turn these records on for the GPS 18 PC, GPS 18 LVC, and GPS 18-5Hz versions, use the $PGRMC1  
NMEA sentence as described in Section 4 GPS 18 PC, GPS 18 LVC, & GPS 18-5Hz Software Interface.  
Refer to the Garmin Device Interface Specification for details on how to form and parse Garmin packets.  
At the time of this printing, these specs are available from the technical suppport section of our Web site:  
Note: For the GPS 18-5Hz, a baud rate of 9600 is not high enough to transmit all of the packets (since they  
are output at a 5 Hz rate). You will need to change the baud rate to at least 38400 to be able to transmit all  
of the packets. Refer to Appendix C: Changing the Baud Rate in Garmin Mode for information.  
For the GPS 18 USB, the two records must be enabled independently by commands to the unit. Refer to the  
Garmin Device Interface Specification for details on how to form and parse Garmin packets over USB. At  
the time of this printing, these specs are available from the technical suppport section of our Web site:  
http://www.garmin.com/support/commProtocol.html. The ID of each command should be 10 decimal to  
signify that the record is a command. The data portion of the packet should be one of the following:  
Function  
Command (base 10)  
Position Record On  
Position Record Off  
49  
50  
Receiver Measurement Record On  
Receiver Measurement Record Off  
110  
111  
Note that the satellite data information is also enabled when the position record is enabled.  
Records sent over RS232 begin with a delimiter byte (10 hex). The second byte identifies the record type  
(33 hex for a position record, 34 hex for a receiver measurement and 72 hex for a satellite data record).  
The third byte indicates the size of the data. The fourth byte is the first byte of data. The data is then  
followed by a checksum byte, a delimiter byte (10 hex), and an end-of-transmission character (03 hex).  
Additionally, any DLEs (0x10) that appear between the delimeters are escaped with a second DLE. There  
is sample code at the end of this section that will strip off the DLEs and ETXs.  
RS232 Packet:  
- 0x10  
(DLE is first byte)  
- 0x##  
(Record ID – single byte)  
- 0x##  
(Number of data bytes – single byte)  
- data bytes  
- 0x##  
(See descriptions below)  
(2’s complement of the arithmetic sum of the bytes between the delimiters)  
- 0x10  
(DLE)  
- 0x03  
(ETX is last byte)  
USB packets contain only the record ID, size, and data payload. Refer to the Garmin Device Interface  
Specification for details on how to form and parse Garmin USB packets.  
USB Packet:  
- 0x##  
(Record ID – single byte)  
- 0x##  
(Number of data bytes – single byte)  
(See descriptions below)  
- data bytes  
The data bytes of each packet contain the record specified by the record ID. A description of each record  
follows.  
GPS 18 Technical Specifications (190-00307-00)  
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Satellite Data Record  
The satellite data has a record ID of 0x72 with 84 (0x54) data bytes. The data bytes contain the data for the  
12 channels as described below. For each satellite, the following data is available:  
typedef struct  
{
uint8  
uint16  
uint8  
uint16  
uint8  
svid;  
snr;  
//space vehicle identification (1–32 and 33–64 for WAAS)  
//signal-to-noise ratio  
elev;  
azmth;  
status;  
//satellite elevation in degrees  
//satellite azimuth in degrees  
//status bit-field  
} cpo_sat_data;  
The status bit field represents a set of booleans described below:  
Bit  
0
1
Meaning when bit is one (1)  
The unit has ephemeris data for the specified satellite.  
The unit has a differential correction for the specified satellite.  
The unit is using this satellite in the solution.  
2
This pattern is repeated for all 12 channels for a total of 12 X 7 bytes = 84 (0x54) bytes :  
typedef struct  
{
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
cpo_sat_data  
} cpo_all_sat_data  
The RS-232 Packet for the Satellite Record looks like:  
- 0x10  
(DLE is first byte)  
- 0x72  
(Record ID – single byte)  
(Number of data bytes – single byte)  
- 0x54  
- cpo_all_sat_data  
- 0x##  
(2’s complement of the arithmetic sum of the bytes between the delimiters)  
- 0x10  
(DLE)  
- 0x03  
(ETX is last byte)  
GPS 18 Technical Specifications (190-00307-00)  
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The USB Packet for the Satellite Record looks like:  
- 0x72  
(Record ID – single byte)  
- 0x54  
(Number of data bytes – single byte)  
- cpo_all_sat_data  
Position Record  
The Position Record has a record identifier of  
typedef struct  
{
float  
float  
float  
float  
int  
alt;  
epe;  
eph;  
epv;  
fix;  
double  
double  
double  
float  
float  
float  
float  
int  
gps_tow;  
lat;  
lon;  
lon_vel;  
lat_vel;  
alt_vel;  
msl_hght;  
leap_sec;  
grmn_days;  
long  
} cpo_pvt_data;  
alt  
Ellipsoid altitude (meters)  
epe  
eph  
epv  
fix  
Est pos error (meters)  
Pos err, horizontal (meters)  
Pos err, vertical (meters)  
0 = no fix; 1 = no fix; 2 = 2D; 3 = 3D; 4 = 2D differential; 5 = 3D differential;  
6 and greater = not defined  
gps_tow  
lat  
GPS time of week (sec)  
Latitude (radians)  
lon  
Longitude (radians)  
lon_vel  
lat_vel  
alt_vel  
msl_hght  
leap_sec  
Longitude velocity (meters/second)  
Latitude velocity (meters/second)  
Altitude velocity (meters/second)  
Mean sea level height (meters)  
UTC leap seconds  
grmn_days Garmin days (days since December 31, 1989)  
GPS 18 Technical Specifications (190-00307-00)  
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Receiver Measurement Record  
typedef struct  
{
unsigned long  
double  
cycles;  
pr;  
unsigned int  
char  
unsigned char  
char  
phase;  
slp_dtct;  
snr_dbhz;  
svid;  
char  
valid;  
} cpo_rcv_sv_data;  
typedef struct  
{
double  
int  
rcvr_tow;  
rcvr_wn;  
cpo_rcv_sv_data sv[ 12 ];  
} cpo_rcv_data;  
rcvr_tow  
rcvr_wn  
cycles  
pr  
Receiver time of week (seconds)  
Receiver week number  
Number of accumulated cycles  
Pseudorange (meters)  
phase  
To convert to (0 to 359.999) multiply by 360.0 and divide by 2048.0  
0 = no cycle slip detected; non-zero = cycle slip detected  
Signal strength - db Hz  
slp_dtct  
snr_dbhz  
svid  
Satellite number (0 to 31; 119 to 138 for WAAS). Note: add 1 to offset to current svid  
numbers.  
valid  
0 = information not valid; non-zero = information valid  
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DLE and ETX bytes:  
Sample C code to receive the two records should filter DLE and ETX bytes as described below:  
typedef enum  
{
DAT,  
DLE,  
ETX  
} rx_state_type;  
/* Declare and initialize static variables */  
static char  
static int  
in_que[ 256 ];  
in_que_ptr = 0;  
static rx_state_type rx_state = DAT;  
.
.
.
void add_to_que( char data )  
{
#define DLE_BYTE 0x10  
#define ETX_BYTE 0x03  
if ( rx_state == DAT )  
{
if ( data == DLE_BYTE )  
{
rx_state = DLE;  
}
else  
{
in_que[ in_que_ptr++ ] = data;  
}
}
else if ( rx_state == DLE )  
{
if ( data == ETX_BYTE )  
{
rx_state = ETX;  
}
else  
{
rx_state = DAT;  
in_que[ in_que_ptr++ ] = data;  
}
}
else if ( rx_state == ETX )  
{
if ( data == DLE_BYTE )  
{
rx_state = DLE;  
}
}
if ( in_que_ptr > 255 )  
{
in_que_ptr = 0;  
}
}
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APPENDIX C: CHANGING THE BAUD RATE IN GARMIN MODE  
In certain cases, you may need to change the default baud rate of your Garmin GPS receiver while in  
Garmin mode. Follow these steps to temporarily change the baud rate.  
Refer to the Garmin Device Interface Specification for details on how to form and parse Garmin packets.  
At the time of this printing, these specs are available from the technical suppport section of our Web site:  
1. Turn off all requests by transmitting packet:  
id = IOP_RQST_DATA (0x1C)  
data = 0 (16-bit unsigned integer )  
2. The GPS unit will respond by sending a packet with id = IOP_ACK_BYTE (0x06)  
3. After you receive the above packet, transmit packet:  
id = IOP_BAUD_RQST_DATA (0x30)  
data = baud rate to change to (32-bit unsigned integer; for example, 38400)  
4. The GPS unit will respond by sending a packet:  
id = IOP_BAUD_ACPT_DATA (0x31)  
data = highest acceptable baud rate closest to what was requested  
(32-bit unsigned integer; for example, 38361 decimal)  
5. Determine the actual baud rate value from the data sent in step 4. This value will be within +/- 5% of  
the actual baud rate. (For example, the GPS unit might send a baud rate of 38361, which correlates to a  
baud rate of 38400).  
6. If the baud rate in step 5 is acceptable, transmit packet:  
id = IOP_ACK_BYTE (0x06)  
data = IOP_BAUD_ACPT_DATA (0x31)  
7. Sleep for a small amount of time, about 100 milliseconds, to make sure the packet in (6) was  
successfully transmitted to the GPS unit.  
8. Close the current connection to the GPS unit and immediately open a new connection with the new  
baud rate obtained in step 5.  
9. Immediately after establishing a connection, transmit packet:  
id = IOP_CMND_DATA (0x0A)  
data = IOP_ACK_PING (0x3A)  
10. The GPS will respond by sending a packet:  
id = IOP_ACK_BYTE (0x06)  
data = IOP_CMND_DATA (0x0A)  
11. After you receive the above packet, transmit the same packet in step 9 again.  
id = IOP_CMND_DATA (0x0A)  
data = IOP_ACK_PING (0x3A)  
12. The GPS will respond again with the same packet in step 10.  
id = IOP_ACK_BYTE (0x06)  
data = IOP_CMND_DATA (0x0A)  
13. The baud rate has been successfully changed upon receiving the above packet. If the GPS unit does  
not receive these two IOP_CMND_DATA packets within two seconds, it will reset its baud rate to  
9600.  
GPS 18 Technical Specifications (190-00307-00)  
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APPENDIX D: GPS 18 PC/ LVC/18-5Hz & WINDOWS SERIAL MOUSE ISSUE  
Problem: It is possible for Windows to incorrectly interpret the NMEA 0183 output of the GPS 18 PC as  
the output of a Microsoft Serial BallPoint Mouse. When that happens, Windows loads drivers for the Serial  
BallPoint Mouse. This causes the cursor to move erratically about the display, clicking, right clicking,  
double clicking, dragging and dropping displayed items as it goes. On Windows 2000 and Windows XP,  
you may not experience the problem if you wait until after the computer is booted before connecting the  
GPS 18 PC to the serial communications port. This problem is not specific to the GPS 18 PC. Any NMEA  
0183 device connected to a Windows computer’s serial port is likely to cause this problem. Below are  
several possible solutions to this problem.  
Note: If your GPS 18 PC came with Garmin nRoute™ Navigation Software, you will not have this  
problem; the unit is programmed to produce data according to the binary format that is described in  
Appendix B: Binary Phase Output Format.  
If you wish to use a different navigation software application with your GPS 18 PC, you will need to de-  
select the “Phase Output Data” option that is discussed in Solution 3 below.  
Solution 1: The easiest solution is to disable the Serial BallPoint mouse in the Device Manager. Of course,  
this solution assumes that you do not need to use a Serial BallPoint mouse with your computer. When the  
wild mouse problem occurs follow the steps below.  
1. Unplug the DB9 connector.  
2. Right-click the My Computer icon on your desktop and select Properties to open Device Manager.  
3. Go to the hardware tab of the resulting pop-up window and click on the Device Manager button.  
4. Right-click on Serial BallPoint Mouse and choose the option to Disable (NOT uninstall) this device.  
Solution 2: Do not plug the DB9 connector into the computer until the computer is turned on and the  
operating system is completely booted up and running. Every time you use the GPS 18 PC/LVC, you will  
need to start the computer and operating system before making the connection between the GPS 18 PC and  
the computer. This solution usually works on Windows 2000 and Windows XP computers.  
Solution 3: Change the default output of the GPS 18 PC/LVC so that it does not automatically send NMEA  
0183 data to the computer (change the default configuration to enable “Phase Output Data”). Use the  
Garmin Sensor Configuration Software, named SNSRCFG.EXE, provided on the Web site to enable  
“Phase Output Data.” SNSRCFG.EXE is included with the latest GPS 18 firmware, available at  
Please note that by enabling “Phase Output Data,” the device will no longer appear as a NMEA 0183  
device to your computer. As a result, mapping applications that expect to hear NMEA 0183 data will not  
recognize your GPS 18 P/LVC until you re-enable the NMEA 0183 output, disabling the “Phase Output  
Data” in the process.  
Refer to Appendix E: Sensor Configuration Software for complete information about downloading the  
Sensor Configuration Software application.  
After the Sensor Configuration Software is installed and running on your computer, follow the steps below  
to change the default data output of the GPS 18 PC, LVC, or 18-5Hz.  
1. Select the GPS 18 PC / LVC or the GPS 18-5Hz from the  
list of sensors and click OK. The Sensor Configuration  
Software opens with the default configuration file for the  
GPS 18, as shown on the next page.  
2. Select Config > Switch to NMEA Mode (or press the F10  
key).  
3. Select Comm > Setup to open the Comm Setup Window.  
GPS 18 Technical Specifications (190-00307-00)  
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4. Select the Serial Port to which the  
GPS 18 is connected. Select Auto  
to have the program automatically  
determine the Baud Rate, or select  
Manual to manually select the  
Baud Rate of the GPS 18. Click  
OK when done.  
5. Click the Connect icon , or  
select Comm > Connect to  
connect to the GPS 18.  
6. To view the current programming  
of the GPS 18, select Config >  
Get Configuration from GPS (or  
press the F8 key). The current  
programming of the GPS 18 is  
displayed in the window, as shown on the  
previous page.  
7. Open the Sensor Configuration Window by  
pressing the F6 key or selecting Config >  
Sensor Configuration.  
8. Place a check mark in the box next to  
“Binary Output Data” to change the GPS  
18 to Garmin Mode. The unit will keep this  
change in the programming until you  
change it again in the software.  
Note: Selecting Config > Switch to  
Garmin Mode (or pressing the F11 key)  
only changes the unit to work in Garmin  
Mode until power is cycled through the unit  
again. For a more permanent change, refer  
to step 8 above.  
9. Click OK.  
10. When you are ready to upload the changes  
into the GPS 18, select Config > Send  
Configuration to GPS (or press the F9  
key). The new configuration is then loaded  
into the GPS 18.  
11. You may disconnect and close the software  
when finished. The software configuration  
can also be saved for future reference.  
Refer to Appendix E: Sensor Configuration Software for complete information about downloading the  
Sensor Configuration Software application.  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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APPENDIX E: SENSOR CONFIGURATION SOFTWARE  
SNSRCFG configures the GPS sensors based on user-selected parameters. Some application features  
include the ability to download GPS sensor configuration, maintain different configurations in files, and  
perform GPS sensor configurations quickly with the use of one function key.  
This section provides a brief overview of the Sensor Configuration Software. Refer to this section when  
using the software to configure your Garmin sensor.  
Downloading the Sensor Configuration Software  
The Garmin Sensor Configuration Software (SNSRCFG.exe) is available from the Garmin Web site. To  
download the software, start at http://www.garmin.com/oem, select the GPS 18, and then select Software  
Updates. The Garmin Sensor Configuration Software (SNSRCFG.exe) is included in the software update  
download.  
Selecting a Model  
After opening the program (snsrcfg.exe), the following  
screen appears. Select the radio button next to the type of  
Garmin sensor you are configuring.  
Connecting to the Sensor  
After selecting the type of sensor, the following window  
opens. This is the Main Interface Screen for the program.  
To configure your sensor, you must first connect to the  
sensor.  
1. Select Config > Switch to NMEA Mode (or press the F10  
key).  
2. Select Comm > Setup to open the Comm Setup Window.  
3. Select the Serial Port to which the sensor is connected.  
Select Auto to have the program automatically determine  
the Baud Rate, or select  
Manual to manually  
select the Baud Rate of the  
GPS 18. Click OK when  
done.  
4. Click the Connect icon  
, or select Comm >  
Connect.  
5. To view the current  
programming of the  
sensor, select Config >  
Get Configuration from  
GPS (or press the F8 key).  
The current programming  
of the sensor is displayed  
in the window shown to  
the right.  
GPS 18 Technical Specifications (190-00307-00)  
Rev. D  
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File Menu  
The File Menu allows you to open, save, and print sensor configurations. The items in the File Menu work  
like most Windows-based programs.  
Comm Menu  
The Comm (Communication) Menu allows you to set the port number, baud rate, and then connect and  
disconnect from the sensor.  
Setup: Opens the Comm Setup Window, shown to the left. Select  
the Serial Port to which the sensor is connected from the drop-  
down list. Then select Auto (the program determines the baud rate  
on its own) or Manual (you then enter the baud rate) for the Baud  
Rate entry.  
Connect: Select Connect to connect to the sensor to change or  
view the configuration.  
Disconnect: Select Disconnect to disconnect from the sensor.  
Config Menu  
The Config (Configuration) Menu allows you  
configure the sensor as it is connected.  
Sensor Configuration (F6): Opens the Sensor  
Configuration Window, shown to the right.  
Many of the fields in this window should be left  
alone. Please refer to the beginning of this  
manual for clarification about some of these  
fields. For the most part, this window is used to  
enter a new Latitude, Longitude, and Altitude  
for the sensor. This is especially helpful when  
you are programming the sensor for use in a  
particular geographic location.  
Resetting the Unit (Reset Unit) performs a reset  
on the unit, much like cycling the power.  
Resetting the non-volatile memory (Reset  
NonVol) will clear all of the data from the non-  
volatile memory.  
NMEA Sentence Selections (F7): Displays the  
NMEA Sentence Selections Window. If the  
sentence is enabled, a check mark appears in the  
box to the left of the sentence name. Click the  
box to enable or disable to the sentence.  
GPS 18 Technical Specifications (190-00307-00)  
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Get Configuration From GPS (F8): Retrieves the current programming from the sensor. The  
programming is then displayed in the Main Interface Window.  
Send Configuration To GPS (F9): Sends the changes you have made to the programming to the sensor.  
Switch to NMEA Mode (F10): Switches the unit to NMEA Mode. The sensor must be in NMEA Mode  
when connected to this software.  
Switch to Garmin Mode (F11): Switches the unit to Garmin Mode.  
Update Software (F12): After you have downloaded a new software version for the sensor, you can update  
the sensor with the new software. Select Update Software and then select the file using the Open dialog  
box. You must locate both the *.rgn file and the updater.exe file.  
View Menu  
The View Menu allows you to view the NMEA sentences transmitted by the sensor. You can also  
customize how the program looks by showing and hiding the Toolbar and Status Bar.  
Help Menu  
The Help Menu displays the software version and copyright information.  
For the latest free software updates (excluding map data) throughout the life of your  
Garmin products, visit the Garmin Web site at www.garmin.com.  
© Copyright 2004–2005 Garmin Ltd. or its subsidiaries  
Garmin International, Inc.  
1200 East 151st Street, Olathe, Kansas 66062, U.S.A.  
Garmin (Europe) Ltd.  
Unit 5, The Quadrangle, Abbey Park Industrial Estate, Romsey, SO51 9DL, U.K.  
Garmin Corporation  
No. 68, Jangshu 2nd Road, Shijr, Taipei County, Taiwan  
Part Number 190-00307-00 Rev. D  
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