I have a need to summarize my spatial data with what I will call a "meta-symbol", i.e., a symbol that represents more than one data column, with more than one state for each column. I could create a symbol file containing all of the combinations of such a symbol, however, this can become a very large group of symbols in very short order.
For example, I have a map which shows geographical regions, and I wish to summarize the drought status of each of those entities for 4 different metric: 1) rainfall, 2) stream flow, 3) groundwater levels, and 4) reservoir storage values. I have 4 categories of drought indicator: 1) no drought, 2) drought watch, 3) drought warning, and 4) drought emergency. I believe that this makes my number of possible combinations, 4^4, or 256 different categories. If I were to add a 5th indicator, then I would end up with 5^4 possible combinations, or 625 different combinations. One possible approach that I have thought of is to create a rectangular grid (with cells for each indicator) for each geographic area, located at its centroid, then place a symbol in each grid cell. This would reduce the overhead to 4 symbols, that would then be dynamically assigned by mapserver to the drought value. I am concerned about registering these properly within the cell. Any feedback on my proposed approach, or examples of something similar would be appreciated, Thanks in advance, r.b. Robert W. Burgholzer Surface Water Modeler Office of Water Supply and Planning Virginia Department of Environmental Quality [EMAIL PROTECTED] 804-698-4405 Open Source Modeling Tools: http://sourceforge.net/projects/npsource/
