very much, 
conducted 
sult required. 
, transparent 
sparent type, 
accuracy but 
flective type, 
anner, 1s for 
e scanner is 
le updating 
curacy is not 
ortant, aerial 
n finer than 
x. However, 
lata size of 
uge. 
on map 
jethods for 
[hose are as 
b. method using digital map transformed into 
central projection 
c. method using affine transformed 
photograph 
Principle of these methods are shown in 
Figure 2. 
(1) Method using orthophoto 
In this method, single photograph is oriented 
using several ground control points first. 
Second, grid with specified resolution is set on 
the digital map. For each grid point, 
corresponding photo coordinate is calculated 
| ; digital photograph 
DEM 
   
  
digital orthophoto 
f S digital map 
(1) Method using orthophoto 
  
  
  
  
digital map 
from orientation parameter and digital 
elevation model (DEM), and pixel value is 
resampled by nearest neighbor or bilinear 
method. The generation of digital orthophoto 
in this way takes much time, but this method 
1s very natural method. 
(2) Method using affine transformed 
photograph 
In this method, more than three control points 
which are distinct both on digital map and 
aerial photograph are selected first. Second, 
affine transformation is determined from 
rl 
digital photograph 
digital map transformed 
into central projection 
  
(3) Method using digital map transformed into 
central projection 
  
  
E ONE 
E 
[| 
  
[^ 
digital photograph 
(2) Method using affine transformed photograph 
Figure 2 : Methods for overlaying photograph on map