This is the 23rd day of my participation in the August More Text Challenge

A, problem,

Because of some requirements I needed to calculate the area of the vector boundary to determine the field area, but I ran into some problems. The way to calculate the area is pretty simple. However, the following problems arise:

1. My layer is in geographic coordinates instead of projection coordinates and cannot calculate area as shown in the following figure: Area – disabled

​

2. After the projection transformation into the projection coordinate system, there is a large difference in the calculated area.

Second, the steps

Software:

Arcgis10.3

Tools:

Projection and transformation tools

So let’s just create a new vector for example

1. Open the layer properties list and create a field to calculate the area (name is optional).

​

2. Right-click the mouse to pop up the option box and select “Geometric Calculation”

​

Under normal circumstances, the above pop-up box will appear. Select the area – coordinate system – unit and click OK

But what we have is the following,

​

The reason is that my layer is in geographic coordinates. Not projected coordinates. The area calculation can only be planar. Projection coordinates = geographic coordinates + projection calculation

Therefore, the geographical coordinates of the irregular ellipsoid should be converted into projection coordinates.

3. Projection conversion

Method 1: Find the position of the table in the directory, right click on the property, and the following box pops up. Select the projection coordinate system from the required coordinate system and define a projection coordinate system for the data

​

Method 2: Toolbox — data management tool — Projection and transformation — projection

​

​

4. During the projection, we choose different projection coordinate systems, and the calculated data are biased. Different geographical locations should be converted into specific projection coordinate systems due to different parameters

Therefore, before the projection, we need to determine the projection coordinate system to be transformed for the data. Generally, it is also associated with the geographic coordinate system corresponding to the data to a certain extent

​