6B-1-4 
RTK-GPS is that because RTK-GPS, unlike DGPS, also 
uses carrier information for position calculation, inter 
ruption of satellite transmissions or correction data 
transmissions due to the surrounding topography could 
result in failure in positioning. 
From the viewpoint of positioning accuracy alone, it can 
be said that RTK-GPS is a GPS technique suitable for a 
construction vehicle monitoring system. Topography of 
Japan, however, is mountainous, and many construction 
projects that use construction vehicles are located in 
mountain areas. Therefore, relative suitability of RTK- 
GPS and DGPS for use in a construction vehicle moni 
toring system needs to be investigated in terms of not only 
positioning accuracy but also the robustness of system 
operation under the influence of environmental conditions. 
6. EVALUATING DGPS AND RTK-GPS BASED 
ROLUNG MANAGEMENT SYSTEMS 
In order to apply GPS to a rolling management system, it 
is necessary to investigate the relative suitability of the 
GPS techniques applicable to the system. Therefore, both 
DGPS and RTK-GPS receivers were installed on the 
rolling management system, and the system was tested 
and the GPS positioning techniques evaluated. 
6.1 CONFIGURATION OF THE TEST SYSTEM 
Figure 6 shows the configuration of the test system. The 
test system is equipped with two types of receivers, 
DGPS and RTK-GPS, so that they can be evaluated. 
"| DGPS Reference \- 1 
Local Reference 
Figure.4 Real-Time Kinematic GPS (RTK-GPS) 
Figure.6 Configuration of the test system 
Table.5 The special feature of RTK-GPS and DPGS 
RTK-GPS 
DGPS 
Accuracy 
2 cm in Horizontal 
5 cm in Vertical 
1 - 2 m in Horizontal 
3 - 5 m in Vertical 
Cost 
About $67,000(US) in Japan 
About $25,000(US) in Japan 
Time to recover after 
Interruption of Satellite 
Transmissions 
1 - 2 miunites after resumption 
of Satellite Transmissions 
At once after resumption 
of Satellite Transmissions 
Positioning mode during 
Interruption of Correction Data 
Transmissions 
Single point positioning mode 
(Interruption of RTK-GPS) 
Continuation for 30 - 90 seconds 
in Interruption of Correction Data 
Transmissions