ArcGIS Application--Four ways to calculate patch area

There are several methods in ArcGIS to calculate the area of the map, this article summarizes four methods, can be called the most complete in history?

1. Calculation geometry

I think this is the best way for non-professionals to use the computational geometry features in ArcGIS directly.

A, first add a double Type field, which is used to store area values.

B. Perform computational geometry operations

Select the corresponding attribute in the dialog box that follows.

2. Field Calculator

The field calculator is a more advanced usage, in which you can edit a personalized script code (VB script or Python) to perform some complex calculations. The calculation of speckle area is one of the simplest applications.

The Python script is as follows:

3. Calculation Area Tool

4. SHP Switch to GDB

Create a GDB (PGDB or FGDB), create a feature dataset, and note that the feature dataset's coordinate system is set to be consistent with the original SHP, and when the SHP data is dumped like GDB, the boundary length and area of the patch are calculated automatically.

A Little doubt

As shown, the identified 1, 2, 3, 4 columns in turn corresponding to the above four calculation area method, observed that the results of method 4 and other three methods have a little difference in numerical accuracy, why?

ArcGIS Application--Four ways to calculate patch area