Features
Maintenance and Care
AL20M, AL24M, AL28M
AL24A, AL28A, AL32A
Auto Levels
01. Focusing knob
02. Sighting guide
• As with all precision instruments, the auto level should be
transported and stored in its carrying case.
• When carrying the instrument mounted to a tripod, be sure
to carry it vertically rather than over your shoulder.
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2
3
13
12
03. Crosshairs’ adjustment screws (under cover)
04. Crosshairs’ focusing ring
05. Eyepiece
06. Horizontal rotation ring and angle index
07. Leveling screws
User Guide
•
• Whenever possible, store the instrument in a dry, shady area.
• Wipe the instrument clean with a cloth. Clean the objective
and eyepieces with special care using a damp tissue or soft,
clean, lint-free cotton cloth.
• When working in wet weather, wipe off the instrument and
carrying case in the field and let them dry completely indoors
with the case open.
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5
11
10
08. Base plate
09. Circular level adjustment screws
10. Horizontal tangent knob
11. Circular level
12. Mirror for reading circular level
13. Objective
6
Safety Information
9
Included in this manual are Cautions and Notes. Each of
these words represents a level of danger or concern. A Caution
indicates a hazard or unsafe practice that could result in
minor injury or property damage. A Note indicates important
information unrelated to safety.
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Establishing an Elevation
1. Set up and level the instrument.
2. Set the grade rod on a known elevation (30.55 m) and take a
grade rod reading (1.72 m).
3. Add the grade rod reading to the known elevation to get the
height of instrument or HI (1.72 + 30.55 = 32.27 m).
4. Subtract the elevation of the point you want to establish
(31.02 m) from the HI (32.27) to calculate the difference
between the two points (32.27 – 31.02 =1.25 m).
5. Go to the point you want to establish and adjust the height of
the grade rod until the calculated difference (1.25) is centered
in the crosshairs.
How to Use the Instrument
Taking Measurements
Setting Up the Instrument
1. Set up the tripod at a height appropriate for your use.
Note: Make sure the tripod is stable and the tripod head is
relatively level.
2. Attach the instrument to the tripod.
3. Level the instrument using the circular level as a reference.
4. Focus the telescope crosshairs by turning the crosshairs’
focusing ring.
Determining the Difference in Elevation
Taking a Distance Measurement
Note: The instrument’s stadia lines allow you to determine the
distance between the instrument and the grade rod.
1. Take readings at the upper stadia
15
line (1.436 m) and the lower stadia
a1
b1
line (1.152 m).
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13
12
11
10
2. Calculate the difference between
the two readings (1.436 – 1.152 =
0.284 m).
3. Multiply the difference by 100
to get the distance between the
instrument and the grade rod
(.284 x 100 = 28.4).
B
Aligning the Instrument
1. Align the telescope to the grade rod using the sighting guides.
A
2. Turn the focusing knob to bring the grade rod into sharp
focus. Precisely sight the center of the grade rod in the
telescope crosshairs using the horizontal tangent knob.
1. Set up the instrument half way between two points (A and B).
2. Take a reading at point A (a1 = 1.726 m) and another one at
point B (b1 =1.259 m).
Note: A slight deviation of the line of sight from horizontal
will not cause any measuring error as long as the instrument
is set up approximately half way between the two points.
3. Subtract b1 from a1 to get the difference between the points
(d = 0.467 m).
Computation Example
Elevation
3. Check for parallax shift.
Note: No parallax exists if the crosshairs and the grade rod
graduations remain in coincidence even when you change
your viewing angle (move your eye up/down and left/right in
front of the eyepiece).
Note: After the bubble in the circular level has been centered,
the compensator corrects residual line-of-sight inclinations.
The compensator does not, however, eliminate any tilts
resulting from inadequate adjustment of the circular level or
line of sight. These must be checked regularly (see Adjusting
the Instrument for more information).
Center Line Reading
Distance Measurement
Upper Stadia Line Reading
Lower Stadia Line Reading
Difference
1.294 m
1.436 m
1.152 m
0.284 m
28. 4 m
Note: Point B is 0.467 higher than point A because the
difference is a positive number. If point B were lower than
point A, the number would be negative.
Distance (0.284 x 100)
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