5. UPDATING SYSTEM FOR 
SCALE TOPOGRAPHIC MAP 
1:2,500 
As large scale mapping is widely demanded, 
the influence of practical simple updating 
system is expected very big. So far, prototype 
systems are built up. 
5.] Characteristics of simple updating system 
for large scale map 
In large scale mapping, as the shape of each 
building should be drawn, small structures in 
the digitized photograph are required to be 
visually clear. Therefore, in this system 
photograph is digitized in high resolution with 
very accurate scanner. As a result, data size of 
digital photograph become very huge, which 
means high performance personal computer or 
engineering workstation is required. In 
addition, digital map data are generally vector 
data, so "method using digital map 
transformed into central projection" is used for 
overlay. 
5.2 Experiment of simple updating using 
prototype system 
Using prototype system, experiment of simple 
updating and accuracy assessment have been 
conducted. The digital map revised by 
prototype system was compared with the map 
revised by ordinary 3 dimensional 
measurement using stereoplotter. Accuracy of 
simple updating method was assessed by root 
mean square of the difference of coordinates of 
corresponding points in these two revised 
maps. Accuracy is calculated for both roads 
and buildings respectively. Table 1 shows 
specification of data used for experiment and 
the accuracy of simple updating method. 
Figure 4 shows revised map by simple 
updating method (solid lines) overlaid on that 
by 3 dimensional measurement (broken lines). 
410 
6. CONCLUSION 
Simple updating system for digital map, 
which does not require special 
photogrammetric instruments but common 
personal computer or workstation and anyone 
can handle easily, has been developed. 
Especially, system for 1:25,000 scale 
topographic map which has developed by GSI 
is very practical and is supposed to be adopted 
in the routine revision work from this year. 
Prototype systems for large scale mapping 
have also developed. Those systems show 
fairy good accuracy, but visual interpretation 
of fine structures on digital photograph such 
as shapes of buildings is difficult unless 
photograph is digitized in very high resolution. 
REFERENCES 
Koide, M., I. Kamiya, T. Yoshinari, and B. 
Urabe, 1992. Raster based  1/25,000 
Topographic Map Revision. International 
Archives of Photogrammetry and Remote 
Sensing Commission IV : 517-522.