Need help with calculating area for land cover

[NitishaShrestha]

Hi,

I am trying to calculate the area for each classification in NLCD land cover data.

I tried adding field in the attribute table but it does not let me use calculate geometry. I also tried using tabulate area from spatial analyst tool but that does not work either. Please help.

Thank You,
Nitisha

[TerrySilveus]

Hi,

I am trying to calculate the area for each classification in NLCD land cover data.

I tried adding field in the attribute table but it does not let me use calculate geometry. I also tried using tabulate area from spatial analyst tool but that does not work either. Please help.

Thank You,
Nitisha

What projection are you using?  I have seen this sometimes when I have it projected for lat/long, when I change to get UTM coordinates, I'm able to also calculate area.  Not sure how it's related, because sometimes I can get area with either projection, but if it's not projected maybe that's why you can't get the area.

[DarrenWiens2]

You can use the Summary Statistics tool (statistics field = area, case field = land class). Or, in the attribute table, right-click the land class column, choose summarize. Expand the area field and choose SUM.

[MatthewNordhagen]

Hi Nitisha - In my opinion the easiest method to calculate area of a land classification raster (be it NLCD or ReGAP) is to do a conditional statement on the raster to make each land type its own raster layer and then convert those raster layers to polygons.  For example, if you have a land type that's called 'Deciduous Forest' you can use the 'Con' tool in Spatial Analyst to create a new raster layer that only has Deciduous Forest.  Once the raster is created you can convert this to a polygon using the 'Raster to Polygon' tool.  The resulting shapefile will include a column called 'Shape_Area' that will give you the area of Deciduous Forest. 

I know there are many ways you can approach this problem but this is the method that I've used personally many time as it's fairly straightforward and quick in my opinion.  Let me know if you need any more help.  Good Luck.

[NitishaShrestha]

What projection are you using?  I have seen this sometimes when I have it projected for lat/long, when I change to get UTM coordinates, I'm able to also calculate area.  Not sure how it's related, because sometimes I can get area with either projection, but if it's not projected maybe that's why you can't get the area.

Thank you for the post. The data is projected as NAD UTM Zone 17N

[NitishaShrestha]

You can use the Summary Statistics tool (statistics field = area, case field = land class). Or, in the attribute table, right-click the land class column, choose summarize. Expand the area field and choose SUM.

Thank you for the post.

I tried Summary statistics but I am not sure what summary statistic I need to choose.

[NitishaShrestha]

Hi Nitisha - In my opinion the easiest method to calculate area of a land classification raster (be it NLCD or ReGAP) is to do a conditional statement on the raster to make each land type its own raster layer and then convert those raster layers to polygons.  For example, if you have a land type that's called 'Deciduous Forest' you can use the 'Con' tool in Spatial Analyst to create a new raster layer that only has Deciduous Forest.  Once the raster is created you can convert this to a polygon using the 'Raster to Polygon' tool.  The resulting shapefile will include a column called 'Shape_Area' that will give you the area of Deciduous Forest. 

I know there are many ways you can approach this problem but this is the method that I've used personally many time as it's fairly straightforward and quick in my opinion.  Let me know if you need any more help.  Good Luck.

Thank you for the post. Before using the spatial analyst tool do I need to make a different shapefile just for Deciduous forest by exporting the data.

What data do I pick for input conditional raster and  input raster or constant value?

[DarrenWiens2]

I guess I might be thinking about your data wrong, but this is what I'm picturing: a polygon shapefile or feature class (vector, not raster), with one attribute column containing the land classification each polygon belongs to, and another column with the area of each polygon.

In the Summary Statistics tool, choose the area column as the statistics field, SUM as the statistic, and land classification as the case field. This will sum the area of each land classification.

[NitishaShrestha]

I guess I might be thinking about your data wrong, but this is what I'm picturing: a polygon shapefile or feature class (vector, not raster), with one attribute column containing the land classification each polygon belongs to, and another column with the area of each polygon.

In the Summary Statistics tool, choose the area column as the statistics field, SUM as the statistic, and land classification as the case field. This will sum the area of each land classification.

It is a raster file. It does not have an area column. I want to generate a table with area for the raster data.

Thank You

[TerrySilveus]

It is a raster file. It does not have an area column. I want to generate a table with area for the raster data.

Thank You

I don't deal with rasters often, but wouldn't you just need to multiply the cell size with the number of cells of a specific value?