How do I know which units that I need to calculate perimeter for my soil data. The field column I have has Perimeter and it has a several nulls that I need to fill it in.
It is a polygon and
it is a NAD 1983 UTM Zone 13 N and Linear Unit is Meter
If the data are projected and the units are in meters, then the units are in meters
unless you made a change in the calculate geometry to report otherwise.... which is why you should always leave your calculations in the units of the data rather than changing them to what you want. Use projected data, leave the units in their base units and alter outside the table not within
You can always add a new field and calculate as metres to check against your known values, but given that you have to make an effort to calculate in units other than the linear unit, it's a safe bet that it's what was used.