identify percentage of raster cells within a polygon

Question

As per the title I want to determine the population inside multiple polygons according to different land use zoning (High Residential, Low Residential, National Parks etc) that's in raster format.

To do this I'm thinking I should calculate the percentage of raster cells inside the polygon and then join the tables so I can calculate the population.

So far I've reclassified these land use zones to make 3 different binary rasters. e.g. For High Res:- 1 for high Res and 0 for the other two (National Parks and Low Res); For Low Res:- 1 for Low Res and 0 for High Res and National Parks.

The next step would be to use "Zonal Statistics by Table" and join the table to the polygon table that has population information. However it seems I'm just adding up polygon population essentially coming out with the same number.

Answer 1

You could convert the raster to points (Conversion Tools\From Raster) and join that to the polygon layer using a spatial join (layer's context menu\Joins and Relates\Join...\Join data from another layer based on spatial location). That gives the option to collect some statistics, as well as provides a field with a count.

The sticky point is that assumes the centroid for the cell equates to the majority of the cell, which might not always be true. In other words, a point could fall within a polygon, but the majority of the actual cell resides in a different polygon.

Depending on your needs, that may not be significant.