pach of 
ic case. 
ate 
Yn) 
2 
(Yo-Yo) 
by f(s,) 
ing, 
minated, 
are 
rst step 
5/, and 
is func- 
EM, is 
tained 
alog) 
te sys- 
inate 
be 
  
  
Projection B 
1.Define X, Y, 
Aem 
aen if” 
2.Compute X, Y4 
and assign — X 
1 Data base g(X,,Y,) 
Scanned map d(X,,Y) 
   
— X 
Figure 3 Generation of a thematic data base using digital image processing 
defined. This is accomplished by measuring several pass points (e.g. grid loca- 
tions) in the map and the scanned map, i.e. by deriving pass points Py (X4; 
Y 1k» AW Using these pass points a best fitting linear affine transforma- 
tion of the type 
x, 54 + bX + el N X HEY (6) 
is computed. Chogsing a suitable size for the data base elements g(X5,Y2), e.g. 
(50m) 2 or (100m)^, finally the geometric processing is carried out. One de- 
fines a data base element location of coordinates X2,Y, and transforms this 
location into the S,V-system by employing projection equations connecting pro- 
jections A and B. Now the data base element has been defined in the map, and 
via equations (6) its location Xj,Y4 within the digital map format can be read- 
ily computed. Its nearest integer location X4,Y, serves to obtain the value 
d(X1,Y4) for the data base element g(X2,Y?) of location X5,Y2. This process 
is repeated for the entire data base. Figure 4 shows an example of a genera- 
tion of a data base for a forested area. 
   
Figure 4 Generation of a data base for a forested area. Left: Portion of 
topographic map 1:200,000 (forested area platter) 
Right: Data base with (50m) 2 element size 
17 
a) mr HERE IE EG RE Ks