6B-1-5 
6.2 TRACKING TEST 
The purpose of the test is to confirm the paths of rolling 
equipment measured with the two types of GPS receivers 
installed on the test system and to measure their 
positioning accuracy. The yard in which the test was 
conducted is a rectangular yard 30 m long and 20 m wide, 
as shown in Photo 8 and Figure 9. In the test, rolling 
equipment was run in the longitudinal direction at 2 m 
intervals, and measurement data were collected. 
Horizontal positioning errors of the RTK-GPS and DGPS 
positioning methods measured in the test were about 2 
cm and 2 m, respectively, as shown by the vehicular paths 
in Figure 9. Thus, the positioning accuracy of DGPS 
measured in the test is not high enough to be used 
independently; it requires a supplementary method to 
improve positioning accuracy. RTK-GPS, on the other 
hand, turned out to be accurate enough. As the per 
centages of effective measurements shown in Table 10 
indicate, however, RTK-GPS-based positioning is prob 
lematic in case of transmission errors or in mountain 
regions. In areas, such as in flatland areas, where con 
ditions for satellite observation and telecommunications 
are favorable, RTK-GPS-based rolling management is 
satisfactory. However, in areas, such as in mountain areas, 
where conditions for satellite observation and telecom 
munications are unfavorable, it is desirable that DGPS- 
based rolling management, which attaches importance to 
the environmental conditions, augmented by a supple 
mentary accuracy-improvement measure be used. 
Photo.7 The test systtem 
on the rolling compaction machine 
Photo.8 The tracking test field 
X(m) 
Figure.9 The trackig of rolling compaction machine