TM 5-6675-317-14
(b) For map generalization, place large-scale map on glass stage and
place small-scale map on table.
(2) Determine photographic and map lens power. Lowest power provides great-
est field of view; highest power provides greatest detail.
NOTE
Photograph and map must be at same relative scale in order to make accur-
ate cartographic corrections.
(a) Determine map scale and photograph scale.
Example:
200 Scale: 1
1 in. = l mi:
RF 1:24,000:
(b) Determine reduction factor (RF)
Example: 200 Scale = RF
1 in. =1 mi = RF
in. on map equals 200 ft of terrain.
1 in. on map equals 1 mi of
terrain.
Reduction factor of map. 1 in. of
map equals 24,000 in of terrain.
of both photograph and map.
in. of terrain.
(l mi =
5280 ft = 63,360 in.)
(c) Determine matching scale S.
Use RF of photograph as l/P and
RF of map as I/M.
Then the scale S can be expressed as photo-
graph reduction factor (P) over the map reduction factor (M).
s = l/M Divided By l/P or S = P/M
Example:
Photograph RF = 1:80,000; Map RF = 1:24,000.
Thus P = 80,000; M = 24,000; and
S = 80,000/24,000 = 3.3.
(d) Use the value of S to determine map lens and photograph magnification.
S Value
Map Lens
Photograph Magnification
1-7
lx
lx-7x
2-14
lx
2X-14X
Example:
If 3.3 is value of S, then map lens of 1X and
either 1X-7X attachment lens or 2X-14X (without
attachment lens) may be used.
4-20
