Perform Multiply (Times) Function on Several Reclassified Rasters Using Python

Question

I have several reclassified rasters (0 = snow cover, 1 = no snow) and I would like to use the multiply function on all rasters that have the same spatial extent. In ArcGIS 10 this function can be performed on only two rasters. Is it possible to do it on multiple rasters in Python?

Answer 1

Actually, this function can be performed on large numbers of rasters at once even in ArcGIS 10 (without scripting). It is equivalent to finding the local minimum, because the product is 1 if and only if the minimum equals 1 and otherwise is 0. You can also obtain a solution using Equal to Frequency, Greater than Frequency, Less than Frequency, or Popularity by comparing the frequency of 1's to the number of rasters. This latter approach yields more specific information than you call for originally: rather than indicating whether snow was ever present, it can tell you the proportion of rasters in which it is present, cell by cell. Retaining such precision in the data is practically guaranteed to produce better models than the crude binary (yes/no, 1/0, present/absent) models often employed in GIS analysis.