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

[KieranMurphy_GISP1]

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.

[DavidPike]

Have you converted your slope values to polygons? Save them as Feature Classes so you can sum the ShapeArea columns on each, if there's not any NoData values, their total area will be the area of the Raster?

[KieranMurphy_GISP1]

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 ?

[DavidPike]

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?

[DanPatterson]

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