I'm working with the WWF ecoregions, which use the GCS_WGS_1984 geographic coordinate system. I have clipped the ecoregions with a species range (consisting of two polygons), but the new attribute table doesn't tell me the new 'clipped' ecoregion areas.
From reading around it seems I need a projected coordinate system to calculate these new areas. However the attribute table of the ecoregions contain area (km2) as well as shape area. Would these have been calculated using a projected coordinate system? If so, is there a way of finding out which one they used?
I am using ArcGIS 10.1 for Desktop.
Best Answer
It should not matter whether it is uses a geographic or projected coordinate system. The only way of finding out would be to look at the metadata. It may or may not have come with metadata.
If it is a shapefile, you will have to right click on the title of the field at the top of the table and click on calculate geometry to update the values.
If it is a feature class in a geodatabase, you will have to do the same thing if the field is something besides SHAPE_AREA. Shape area should be updated as edits are made and saved.
If you have a custom field, this will have to be recalculated by using the calculate geometry. Also, note what the map units are set to. It is not necessarily what you name your labels.