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Zonal Statistics

August 11 2010 | 0 comments
Categories: Map Data

Thanks, I am actually interested in the area of the burnt cover in each land cover classification within some countries in Africa. Is Zonal Statistics as Table the right function to use? If so, which of the fields gives me the value of the burnt area? How can I get the area in either hectares or kilometers?

Mapping Center Answer:

Both the Zonal Statistics and Zonal Statistics as Table tools will only give you statistics about the ALL the values in the zone, not specific ones, like the burned area.  To get the statistics you are looking for, use the Combine tool -- it is in the Local toolbox in Spatial Analyst. This tool combines multiple rasters so that a unique output value is assigned to each unique combination of input values. So any unique land cover withing the various fire areas will have a unique value. You also get the count of pixels in the output.

To determine the amount of area, multiply the number of pixels (the COUNT field in the attribute table) by the ground area that each pixel represents (this is based on the units of the projection that is used for the rasters). If you have to covnert between different units (e.g., ha or km) use the conversion constants table to do the math.

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