Hello, hope you are well. I have to be able to calculate the percentage of area in a polygon of a raster. I have created a slope map, and have one area that is less than or equal to a certain percent, and the rest is above that percent. I am tasked with f

Question

Hello, hope you are well. I have to be able to calculate the percentage of area in a polygon of a raster. I have created a slope map, and have one area that is less than or equal to a certain percent, and the rest is above that percent. I am tasked with figuring out what percentage is in each category. What tool or process can I use ? Thank you.

DanPatterson · Answer

If you are trying to summarize a raster with respect to a polygon featureclass's polygons, then you might look at

Zonal Statistics as Table—Help | Documentation

Zonal Histogram—Help | Documentation

DavidPike · Answer

Hi mate,

By polygon do you mean the extent of your raster?

I'm assuming you've used Raster Calculator or Con etc. to recode/reclassify the original slope raster? As changing the symbology in the map will not affect the data values.

Raster to Polygon—Help | ArcGIS for Desktop

would allow you to see the Shape_Area of your polygons - I would just select by attribute then right-click on the field in the attribute table and see the sum statistics for each. Be aware of the simplification options as this would change your percentage areas.

Or,

Just look at the raster attribute table

Build Raster Attribute Table—Help | ArcGIS for Desktop

You'll see a count of the number of cells for each type, then it's a case of calculating the percentages of each.

Again, beware of how you want to handle NoData values (if there are any), such as hydrology in your AOI, are they excluded from the percentage calculation or to be included in the total area?

KieranMurphy_GISP1 · Answer

David-

Thank you for your response !

No, I have not converted the slope values to polygons.

Actually, I do not know how to do that.

Is there a tool for that ?