6B-1-1 
A Tracking System for Construction vehicles with DGPS and RTK-GPS 
Shun’ichi OHTSU, Tomonori TAKADA, Tatsunori SADA 
Technical Research Institute, Mitsui Construction CO., LTD. 
518-1, Komaki, Nagareyama-city, Chiba, 270-0132 
JAPAN 
E-mail: ohtsu@mcc48.mcc.co.jp 
KEY WORDS: GPS,DGPS,RTK-GPS, Tracking system 
ABSTRACT 
In recent years GPS technology has been introduced to operation control of construction vehicles, especially tracking the 
rolling compaction machine. Tracking System using GPS is applied to embankment quality control which has been usually 
executed by physical compaction test on the road construction in Japan.There are two real-time positioning and tracking 
systems by GPS, one is differential GPS(DGPS) and the other real-time kinematic GPS (RTK GPS). Users can get 
meter-level accuracy easily with DGPS which employs pseudorange meas-urement.Especially, in Japan, the DGPS 
service by FM multiple broadcasting is spread all over the country for the vehicle navigation users, therefore, DGPS is 
available with low cost at any place where FM can be received. On the other hand, RTK GPS employs a method carrier- 
phase differential GPS positioning whereby users can obtain centimeter-level position accuracies in real time. But users 
have to set local broadcasting system and the devices are more expensive than those of DGPS. The authors developed a 
monitoring system for such construction machine operation using both DGPS and RTK GPS and evaluated both methods. 
The system consists of GPS receivers, communication systems ( FM receiver, local com-munication system), monitors 
and multi gate station (MGS). MGS receives multi receivers outputs ( DGPS and RTK GPS) changes the data formats and 
sends the final outputs to the monitoring system. We had executed an experiment to compare both methods in accuracy , 
stability, and operability on the road construction field. As a result, we obtained 2 meter accuracy by DGPS and 2 cm 
accuracy by RTK GPS, but there were some problems in RTK GPS about stability and operability. We concluded that 
users should select the positioning and tracking method according to the accuracy requirement and other circumstances. 
1. INTRODUCTION 
In Japan, work has been under way in recent years to 
develop GPS (Global Positioning System)-based systems 
for managing construction vehicle operations. Many re 
searchers are working, in particular, on the development 
of systems that manages the quality of rolling by tracking 
rolling equipment locations in real time by means of GPS. 
High-accuracy GPS technology includes two real-time po 
sitioning techniques: Differential GPS (DGPS) and Real- 
Time Kinematic GPS (RTK-GPS). DGPS and RTK-GPS 
provide real-time positioning accuracies of up to several 
meters and several centimeters, respectively. In Japan, 
DGPS service via FM multiplex broadcasts is available to 
drivers in almost all parts of the country so that an 
inexpensive DGPS system can be made a reality if posi 
tioning accuracies of several meters are acceptable. An 
RTK-GPS system, on the other hand, requires its own 
reference station which transmits correction information. 
RTK-GPS, therefore, is more expensive than DGPS 
although the former is capable of more accurate posi 
tioning. 
The authors examined different GPS-based positioning 
techniques to find a method suitable for monitoring con 
struction vehicles, taking into consideration characteristics 
of DGPS and RTK-GPS. Then, the authors developed a 
monitoring system which makes combined use of DGPS 
and RTK-GPS. This paper reports on the development 
and application of a construction vehicle monitoring sys 
tem using DGPS and RTK-GPS, focusing on the veri 
fication of DGPS and RTK-GPS, on DGPS- and RTK- 
GPS-based monitoring of construction vehicles, and par 
ticularly on rolling work that requires real-time vehicle 
management.