ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 
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DIGITAL MODEL AND GPS BASED PATH REPRESENTATION AND OPTIMIZATION 
Linyuan XIA 
National Laboratory for Information Engineering in Survey, Mapping and Remote Sensing, 
Wuhan University, 129#Luoyu Rd.,430079 Wuhan, China 
Tel: 86-27-87881292, fax:86-27-87863229,e-mail: Inyx@hp01 .wtusm.edu.cn, Iyxia@hpb1.wtusm.edu.cn 
Jingnan LIU 
President office, Wuhan University, 129#Luoyu Rd.,430079 Wuhan, China 
Tel: 86-27-87884841, fax: 86-27-87863229, e-mail: jnliu@wtusm.edu.cn 
ABSTRACT 
A multi-purpose path representation and optimization system is introduced in this paper. Path analysis can be performed in two 
ways:(1)design and comparasion on digital elevation map(DEM)(for initial planning). (2)path evaluation and optimization with GPS 
navigation aiding(for practical assessment). Digital model can be generated as DEM by Open Graphical Library with standardARC INFO 
data format or with other data format transferred. When implemented with practical GPS navigation data, environmental influence such 
as multipath interference can be given and point data quality plus reliability can be denoted on the map. Moreover, if a path is selected by 
mouse on the map, possible navigation accuracy by GPS is also indicated for path planning reference. The system can be used for fine 
farming, vehicle highway profiling, aircraft forestation and field investigation. 
1. INTRODUCTION 
With the rapid development of geoinformatics and spatial 
technologies, revolutionary innovations for geography and its 
related subjects have occurred. Geoinformatics based 
application such as resource management, environment 
conservation, traffic control and management, surveying and 
mapping is becoming more and more popular and important, and 
is gaining daily progresses. One of these development trends is 
the integration of spatial technologies(RS,GIS and GPS ). In the 
integration application, GIS is the base for comprehensive 
application and analysis. Deren Li has developed 3S integration 
system of ITS(Deren Li,2000), GPS combined with other 
sensors is employed as road network generation(Deren 
Li, 1999) . David Tyler used GPS as data collecting sensor to 
form DTM for an agricultural GIS( David Tyler,1992). American 
Institute of Navigation(ION) designed a AIRPLAN system to 
carry out flight routine planning with the global DTM base. In 
these application, DTM or DEM data source can be from RS, 
digital input or satellite image and it may be global or regional 
coverage according to the application purpose of the geomatics 
system. The digital mode(DTM or DEM) is an important 
component in the database of GIS and forms a basis of terrain 
data and topographic analysis. 
In thsis paper, a DEM is employed as a means of an area terrain 
representation to depict the earth’s relief, GPS receiver Is 
equipped into a dynamic object(vehicle or low flight plane) to 
collect data and achieve navigation. The positioning data is 
post-processed(differentiated if necessary) to get point position. 
Flight path or traveling path is then denoted on the DEM. Open 
GL approach is used to form moving terrain along the path to 
show the dynamic geographic environment. As an option, the 
terrain induced multipath influence on navigation and satellite 
distribution on the sky is indicated on the dynamic terrain map. 
Zooming local comparasion and optimization can be carried out 
in the software system. 
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Figure 1. Start Up Of The Software 
2. SYSTEM CONFIGURATION AND DATA REPARATION 
In this analysis system, spatial modeling of the regional terrain is 
described by DEM. Source data is archived in format of standard 
ARC/INFO. To achieve the display of DEM and the related 
analysis, the source data is extracted and decoded firstly, and 
then data points are synthesized by the principle of efficiency 
and accuracy, efficiency is mainly the computation speed and 
accuracy is the display equality and modeling fitness(source 
data equality is not discussed here). In this process, a proper 
number of important points are selected and filtered to form 
some intermediate layer files for later display and analysis. This 
can reduce the burden of too dense points and large data 
quantity. The general chart is as follow.