TM 5-6675-324-14
NOTE
Factory determined RT value is given on Calibration Records Sheet
provided with equipment. Alinement is performed as a check.
(7) Place planimeter near shape to be measured so that length of tracer arm
lies along imaginary line through center of shape. Set wheels so that axles form 90
degree angle with tracer arm.
(8) Make practice trace to be sure tracer arm will cover area in one
operation.
(9) Determine area constant, C (multiplier), using the following formula:
(S C ) 2 x
AT
C=
RT
C = Area of constant
= Area of test rule (given on Calibration Records Sheet
AT
provided with equipment)
= Encoder count for each revolution (given on Calibration Records
RT
Sheet provided with equipment)
Sc
= Scale ratio
(a) Determine Sc by using the following formula:
Sc
=
CL
R
X
L
Sc
= Scale ratio
= Length constant (paragraph 5-6.2ad)
CL
= Counts per inch (given on Calibration Records
RL
Sheet provided with equipment)
CL value (0.018447) obtained from linear measurements on aerial
photographs (paragraph 5-6.2.ad).
Sc
= 0.018447 X 724 = 13.355628
= 178.372799
(SC)2
For this example, the value for RT is 2157 and AT is 12.54.
The formula can now be computed on the calculator.
178.372799 X 12.54
2236.794903
.
= 1.036993
C
2157
2157
6-86
