TM5-6675-326-14
6-6.2.33 Area Measurements on Aerial Photographs of Unknown Scale or
Magnification - Continued
g .
Place planimeter near
tracer arm lies along
shape.
Set wheels so
arm.
shape to be measured so that length of
imaginary line through center of
that axles form 90° angle with tracer
h .
Make practice trace to be sure tracer arm will
one operation.
i .
Determine area constant, C (multiplier), using
formula:
cover area in
t h e f o l l o w i n g
Area of constant
Area of test rule (given on Calibration Records
Sheet provided with equipment)
Encoder count for each revolution (given on
Calibration Records Sheet provided with
equipment)
S c a l e r a t i o
( 1 ) D e t e r m i n e Sc by using the following formula:
Sc =
S c a l e r a t i o
CL = Length constant (para 6-6.2.32)
RL = Counts per inch (given on Calibration Records
Sheet provided with equipment)
(2) Example:
U s e g i v e n RL value (724) on Calibration
Records Sheet and CL value (0.018447) obtained from
linear measurements on aerial photographs (para
6 - 6 . 2 . 3 2 ) .
S c =
0.018447 X 724 = 13.355628
SC2
= 178.372799
6-90
