PECamp

Calculate area of raster data in polygons

Discussion created by PECamp on Feb 24, 2014
Latest reply on Feb 25, 2014 by PECamp
This appears to be a seemingly easy calculation. But I am having problems.  

Question: What is the percentage of a certain land cover class in each census block?

Data:
1) Census polygon
2) Land cover raster

Method: Tabulate Area tool - with census polygon as my zone and land cover as the class of interest.

Problem:  My output gives me areas much BIGGER than my census polygon (i.e. Percent land cover class is often greater than 100%...sometimes in the 1000s%).  These numbers are obviously incorrect, as area of vegetation can't be greater than the area of the census block (zone).  Both have linear units of meters and are projected.

What am I doing incorrectly?  Are there better ways to calculate area of raster in polygons?

Thanks in advance,

PC

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