How to get a total amount of cells per classification type in a raster in ArcGIS 10.1?

Digging into Rasters: Getting a Cell Count Breakdown in ArcGIS 10.1

So, you’ve got yourself a classified raster, huh? Think of it like a digital map where each color (or number) represents something different – maybe land cover, like forests, fields, or urban areas. Now, wouldn’t it be cool to know exactly how much of each “something” you have? That’s where counting cells comes in, and it’s surprisingly easy to do in ArcGIS 10.1.

Why bother counting cells? Well, imagine you’re a conservationist tracking deforestation. Knowing the exact area of forest lost over time is pretty darn important, right? Or maybe you’re a city planner figuring out how much land is dedicated to residential versus commercial use. Cell counts give you the raw data to make those calculations and informed decisions.

The secret weapon here is something called a “raster attribute table,” or RAT for short. Basically, it’s a spreadsheet that lives alongside your raster, keeping track of each unique value (your “forest” or “urban” categories) and, crucially, how many cells have that value. Think of it as a census for your raster!

Now, let’s get down to brass tacks. Here’s how you can get those cell counts:

A couple of gotchas to watch out for:

• Missing “COUNT” Field: Sometimes, the “COUNT” field might be MIA. If that happens, try running the “Int” tool again, even if your raster is already an integer. For some reason, that sometimes kicks ArcGIS into gear. You can also try running the “Build Raster Attribute Table” tool again.
• “NoData” Blues: Cells with “NoData” values (meaning they don’t have a classification) won’t be included in the RAT. Keep that in mind when you’re interpreting your results. It’s like having blank responses on a survey – you need to account for them.

Okay, so the RAT method is usually the simplest way to go, but there’s another trick up our sleeve: Zonal Statistics. This is super handy if you want to count cells within specific zones defined by another dataset.

So, there you have it! Whether you’re a seasoned GIS pro or just starting out, knowing how to count cells in ArcGIS 10.1 is a valuable skill. It lets you unlock the hidden information in your raster data and make smarter, more informed decisions. Now go forth and count!