topic Re: Area Calculation in ArcGIS Online Questions

Area Calculation

BradyHay — Tue, 17 Jan 2023 19:46:11 GMT

Hi all,

I'm new to ArcGIS and usually utilize it as an intermediate for transferring data into CAD. I've recently received several map files which classify the habitat suitability rating for several local species and am trying to obtain the areas for each classification within a new boundary. The layer is a TIFF with no attribute table so I'd be extremely grateful if anyone has any recommendations for a quick way to generate areas within ArcMap or how to export the layer as linework or polygons so the areas can be calculated in CAD. Thanks in advance!

Re: Area Calculation

SteveCole — Tue, 17 Jan 2023 22:32:09 GMT

In Arctoolbox, Conversion Tools->From Raster->Raster to Polygon will convert the pixel values to vector polygon features which will be easier to import into CAD. There are a couple options to help simplify the polygon boundaries which will help eliminate the raster "jaggies" that happen when you convert raster to vector.

If you just want the area tally, your legend in your screenshot already tells you the number of pixels per category. Jot down that number and then look at the raster properties for that layer to determine what area the pixel represents (10m x 10m = 100 square meters). Simply multiply the area by the number of pixels to determine the total area represented.

Steve

Re: Area Calculation

BradyHay — Wed, 18 Jan 2023 16:47:09 GMT

Much appreciated Steve! I did try utilizing ArcToolbox to convert everything to polygons but it does give me an error code stating that the input file isn't valid for the parameter.

Using the pixel count to calculate areas definitely sounds like the way to go! I am looking for the area within the M 197 boundary I have in the file (polygon). Is there a way to set the M 197 as the new boundary and and then utilize the pixel count within the new boundary?

Re: Area Calculation

SteveCole — Thu, 19 Jan 2023 16:13:38 GMT

Looks like you have a few options to chose from. Here's ESRI's explanation of what that error you encountered is. Based on you screenshot, the raster values are integers, so I would try converting your original raster to an integer based raster using the Int() tool as suggested in my link above. Once you have an integer based version of the raster, it "should" convert to polygons just fine.

Of course, this just converts the entire raster and doesn't give you just the area within the M 197 boundary you mentioned. One way or another, you have to clip the raster by the M 197 area in order to get that subset of information. To just simply clip the raster, go to ArcToolbox and then-

Data Management->Raster->Raster Processing->Clip and then specify your M 197 dataset as the output extent layer (be sure to check the box 'Use Input Features for Clipping Geometry'). Once the tool finishes and adds the result to your map, just go to the symbology tab of the layer options and you'll see the pixel count as you did before.

If you end up converting the entire raster to polygons, then use Analysis Tools->Extract->Clip in ArcToolbox to clip the new polygons by the M 197 boundary.

Re: Area Calculation

BradyHay — Thu, 19 Jan 2023 20:56:07 GMT

Much appreciated Steve! my license won't allow me to utilize the int tool or raster calculator but using the pixels after clipping the raster works!

Re: Area Calculation

SteveCole — Thu, 19 Jan 2023 21:19:39 GMT

It sucks that your license level prohibits you from working the Spatial Analyst option but I'm glad you're able to get your answer from my other, indirect way.