Raster Calculator Problem

Question

I am trying to perform a sedimentation analysis for a watershed. I have created multiple rasters that I need to multiply together.  When I multiply the four rasters together with the raster calculator I have negative and positive values.  However, the lowest value in the rasters being multiplied is zero.  I can multiply up to three of them together without this happening but all four seems to add negative values.  I am using ArcGIS 9.3.1 and all rasters have the same projection, cell size, and are in a GRID format. Any ideas as to why negative values are showing up?

curtvprice · Answer

I am trying to perform a sedimentation analysis for a watershed. I have created multiple rasters that I need to multiply together.  When I multiply the four rasters together with the raster calculator I have negative and positive values.  However, the lowest value in the rasters being multiplied is zero.  I can multiply up to three of them together without this happening but all four seems to add negative values.  I am using ArcGIS 9.3.1 and all rasters have the same projection, cell size, and are in a GRID format. Any ideas as to why negative values are showing up?

You may be able to solve this mystery by using the identify tool to compare the values in the four inputs and the output for individual locations.