ISPRS Workshop on Service and Application of Spatial Data Infrastructure, XXXVI (4/W6), Oct.14-16, Hangzhou, China 
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(b) Test field B 
100m 
-—“► 
100m 
(a) Test field A 
Figure 2. Test field 
X 
300m 
► Y 
SOcrn^ 
differences vector 
fa) Differences of vector at Field A 
(b) Differences of vector at Field B 
Figure 3. Differences of vector 
2. CONCEPT AND SYSTEM OF REAL TIME GIS 
“REAL TIME GIS” is the system for real time mapping and 
updating the Map at the field site using RTK-GPS and GIS. It 
can be connected with cellular phone through which the stored 
data can be transmitted to the host computer with GIS database. 
Figure 1 shows the concept of “REAL TIME GIS”. Position of 
gas pipe was measured by RTK-GPS as shown in the left side of 
figure. Measured position data are sent to mobile phone by 
wireless system. GIS data will be transferred to GIS server 
through mobile phone as shown in the right side of figure. Then 
the existing GIS data are immediately updated. “REAL TIME 
GIS” was defined by us. 
However, GPS data did not correspond to standard of Japanese 
geodetic system because BESSEL ellipsoid and Tokyo Datum 
had been adopted general standard geometry until 31 March, 
2003. If we directly use GPS data to digital map, geodetic 
system has to cause the coordinates transformation between old 
system and new system. 
3. CONTROL POINT FOR CONVERSION 
To convert the base map, the control point was made by using 
relative positioning GPS. In the research, control point means 
the point which shows both exact coordinates of Tokyo Datum 
and JGD2000. The verification area has the accurate data of 
Tokyo Datum (based on BESSEL ellipsoid and rectangular 
plane coordinate system), and it was generated for town 
planning recently. Experiment areas are “Area A” and “Area B” 
(After this, it is marked A and B). A and B has 14 control points 
and 19 control points respectively. Rectangular size of A and B 
is about 400m and 1000m respectively. To obtain coordinates