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The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics
Chen, Jun

ISPRS, Vol.34, Part 2W2, ‘'Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001
Figure5. Path Terrain Quick Scanning
Besides, the altitude of path can be adjusted to observe the
terrain effect at different heights. This is important when the
inter-visibility conduct is needed in case of communication
device layout, or foresting by airplane, or fine farming
investigation. In some complicated situation, when the satellite
line-of-sight is cut off and the number of navigation satellites are
reduced, GPS navigation will become a problem and this will be
dangerous for flight. It is quite essential to indicate this
information for related parts of path on DEM.
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Figure6. Path Evaluation And Information Indication
Under this circumstance, the terrain induced environmental
influence on GPS positioning is also studied and is indicated on
a right windowed column for user reference. The window also
includes navigation accuracy by GPS. The satellite cut off by
terrain is denoted with a red color line. Zooming is provided to
show regional parts of the path in complicated terrain situation. 3
levels of zooming is supported by the system.
In some situation, it is useful to know the availability of GPS
ahead of a specified time span at an appointed place. In this
software system, the terrain induced visibility of GPS is taken
into consideration. GPS satellite predicted positions in the sky
are calculated from almanacs files. The position plus terrain
factors determine the predicted GPS visibility and possible
positioning accuracy( DOP values).
The software system is an integrated analysis tool for path
planning and investigation by GPS navigation.
Figure7. Predicted Satellite Visibility Sky Plot
Figure8. Predicted Positioning DOP Curve
Function of DEM generation from other data source such as RS,
electronic DTM map is to be included in. rapid compression
algorithm for DEM or DTM generation is still to be discussed
to speed up the whole system.
The first author of the paper would like to thank Professor Du
Qinyun, ,Dr. Wenpin Jiang, Dr. Su Kang and Dr. Yan Li for their
support for the project. Part of the research has been supported
by National Science and Technology Foundation for Surveying
and Mapping under contract number 99011. The research is also
supported by the cooperation project from China General
Company Of Aviation And Aeronautics.
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Linyuan xia: Associate Prof., Graduated from Wuhan Technical
University of Surveying and Mapping in 1986(Geodesy).
Research field: GPS and related application.