control points by least square method. Finally, 
aerial photograph transformed by the affine 
transformation is overlaid on digital map. 
This method is not suitable for hilly or 
mountainous area due to local distortion by 
topographical effect, but this is effective for 
flat area which include most of urban area and 
does not require DEM. 
(3) Method using digital map transformed into 
central projection 
After single photograph orientation is 
conducted, digital map data is transformed 
on aerial photograph using orientation 
parameters and DEM. In case the digital map 
is represented by vector data, calculation time 
is much reduced. 
3.3 Visual extraction of changed parts and edit 
In simple updating system, map data and 
aerial photograph are overlaid on the computer 
display, visual extraction of changed parts 
and edit can be done simultaneously. 
However, as stereoscopic viewing cannot be 
applied and visual interpretation is performed 
on the computer display, interpretation is very 
difficult for some objects. 
Experiment of 1:2,500 scale map revision by 
simple updating system shows, when 
1:12,500 scale photograph used in experiment 
is scanned with from 12.5 pm to 25 pm pitch, 
- interpretation of roads can be done for the 
photograph scanned with any scanning pitch 
- interpretation of building, which needs to 
get the shape of each, requires the photograph 
scanned with finer than 15 pm pitch. 
Practically, scanning pitch should be coarser 
than 25 pm from the point of data size. 
Therefore, in case interpretation is difficult, 
changed parts should be extracted using non- 
digital stereo photographs. 
As for software for edit, not only specially 
developed software but also several 
commercial CAD software can be available. 
408 
4. UPDATING SYSTEM FOR 1:25,000 
SCALE TOPOGRAPHIC MAP 
Our institute, GSI, is responsible for 
maintaining 1:25,000 scale topographic maps 
which are largest scale maps covering whole 
Japan. In order to conduct revision work of 
these maps smoothly, digital revision method 
has been developed and is supposed to be 
adopted as the main revision method (Koide 
et al,1992). As the method for getting 
changed parts, the simple updating method is 
newly included, adding to the ordinary stereo 
method using stereoplotter. In the following, 
rough flow of the digital revision system for 
1:25,000 scale topographic map and the 
simple updating method in this system are 
described. 
4.] Flow of digital revision for 1:25,000 scale 
topographic maps 
(1) Generation of digital map of raster type 
Digital map of raster type is generated after 8 
original plates for each topographic map are 
scanned with 25 pm by very precise scanner 
and overlaid precisely. From second revision, 
this step 1s not required. 
(2) Acquisition of data of changed parts 
Changed parts are acquired in vector form 
from stereo photographs oriented in the stereo 
plotter with encoder. Or simple updating 
method is adopted. That is, after single aerial 
photograph or existing large scale maps are 
scanned by A4 size scanner and overlaid on 
the raster map, changed parts are recognized 
visually. 
(3) Editing on workstation 
Using raster editing program developed by 
GSI, data of changed parts are edited 
according to map specification. 
(4) Film output for printing 
Revised ı 
plotter. 
4.2 Meri 
1:25,000 
This syst 
for map 
aerial ph: 
work 1s n 
which ca 
is expen 
Second, : 
(up to 10