STUDY AND PRACTICE ON NATIONAL MAIN WATER DATA MAKING EACH
RIVERS ARCS IDENTICAL ENTITY
D. Liu, S. Su
Chinese Academy of surveying and Mapping
dongqin@casm.ac.cn
Linear geographical entities/features such as
rivers and roads are presented by series arcs which are spatially end in end in
traditional geographic database. Although they are belongs to an identical
entity, each part has no additional information except the location relation.
In order to better use these data, the paper
presents the method of how to make the arcs that represent the
same river have a unique attribute value. The main process includes the
followings. Firstly we gain the NAME and CODE information of 1:1000000 main
river data by location-matching the river data between 1:250000 and 1:1000000
database. Secondly we calculate the STRAHLER-rank(order) of each river arc
according the STRAHLER rules except those whose rank are higher than 5 or those
who have names or codes. Thirdly based on foregoing work, we judge which arcs
are belong to a same river according to flow direction and STRAHLER-rank, and
then assign them an identical value. By cycling calculate we have accomplished
the task that each arc has gained the identical value of the river that it
belongs to. The finally result is that each river of the main water data of the
whole national scope has obtained the identical value that is different with
others. The paper also shows some of the advantages of using the result
mentioned above.
The main significance of the processing is that
it can help the cartographers save the time when they use these data making
topographic maps, and it can also provides the convenience for GIS users in the
spatially analysis.