STUDY AND PRACTICE ON NATIONAL MAIN WATER DATA MAKING EACH RIVERS ARCS IDENTICAL ENTITY
D. Liu, S. Su
Chinese Academy of surveying and Mapping
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.