ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
(3) Press + 2 twice to get to ID 32. Record the
elevation in feet.
Memory Matching Procedure.
(4) To obtain the geodetic (true) azimuth for a
a. General. The IMU test and alignment procedure
grid azimuth:
is a lengthy (about 8 hours) test sequence which thor-
oughly checks out the IMU and recomputes many of
(a) Press GAZ/TAZ. Record GAZ.
the software calibration parameters if no hardware
(h) Press G A Z / T A Z again. Display will show
malfunctions are found. Most of the testing is per-
TAZ C-E.
formed automatically under computer control. The
maintenance technician is required to reposition the
(c) Press ENT. Record TAZ.
system and measure angles with a theodolite to cali-
brate the porro prism. Care must be taken to site the
(d) Subtract GAZ from TAZ.
system so it remains motionless during the test and is
(e) Add the grid azimuth of the orienting line
properly oriented. The system must be provided with
to the difference to obtain the geodetic
survey coordinates so it can properly compute the
azimuth.
calibration constants. The computer memory used for
the test becomes matched to the IMU.
TAZ
3902.61
Example:
-3903.15
GAZ
b. Test Equipment and Materials.
-0.54
+ 1245.23
(1) PADS test set consisting of the signal proces-
Orienting line grid
sor unit (SPU), punched tape reader (tape reader), buffer
azimuth
unit, interconnecting cables and auxiliary equipment.
1244.69
Geodetic (true)
(2) Teletypewriter. The 100-wpm motor-worm
azimuth of
gear must be installed prior to use. Refer to TM 11-
orienting line
5815-200-12.
(3) PADS power supply, computer, pallet frame,
f. Siting. The system must be on a level, stable
batter box, and CDU.
surface which will not move during the test. Surfaces
(4) +28V power source.
which are unacceptable include: maintenance van floor
or workbench, wooden floors, mud, snow, ice, loosely
c. Survey Requirements. The survey parameters for
packed sand, slippery clay, etc. Acceptable surfaces
a test site will be provided by an engineer survey unit.
include: concrete, dry packed earth, etc. Hot blacktop
The parameters required are:
may allow the system to sink slightly. Distribute the
(1) Latitude, in degrees, minutes, and seconds,
load on blacktop and surfaces such as packed sand and
accurate to 5 arc-seconds.
gravel by placing the system on the base of a transit
case or a four foot square of 3/4-inch-thick plywood or
(2) Elevation, in feet, accurate to 30 feet.
similar material. The surface must be smooth enough so
(3) Geodetic azimuth, in roils, accurate to 0.02
the system does not rock. A surface which can be
roil.
d. The azimuth orienting line must be located so
sand to fill the gravel voids and provide a smooth level
the maintenance technician's theodolite is between 6
surface.
and 16 meters from the IMU porro prism and the
technician can autoreflect on the porro prism. The
porro prism will be oriented approximately 45 degrees
g. Normally, the alignment surface will be outside
a maintenance van. It must be close enough so the
to the cardinal headings. (See figure 4-9.)
cables from the test equipment will reach the system
e. If only UTM coordinates, elevation in meters,
while the test equipment remains in the van. The
and/or grid azimuth are available, the system can be
alignment surface must be situated so the porro prism
used to translate them to the proper quantities as
can be observed from the orienting line (refer to para-
follows:
graph 4-11c.).
With the operational program installed in
(1)
memory, perform the test shown in table 3-1.
h. Test Procedure. Perform the test in accordance
Use the correct values for casting, northing,
with table 4-14 or 4-14.1. Table 4-14 uses PADS test set
and elevation.
tape reader, part no. 877406-1 and table 4-14.1 uses
tape reader, part no, 877406-2. Table 4-15 is a sample
After elevation is entered, press: MON, ID,
(2)
printout from an IMU test. An interconnection diagram
3,0, ENT. Record the displayed latitude in
is provided in figure 4-8.
degrees, minutes, and seconds.
4-78
Change 5
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