Error when changing from WGS 1984 to WGS 1984 Web Mercator coordinatesystem with Python generated shapes

Question

I've used Python code to transform buffers into elongated ovals, intended to visualize the area where volcanic ash would settle during an eruption. These modified buffers were based on the standard WGS 1984 coordinate system. However, the issue arises when these shapes are loaded onto a map in the Web Mercator view. Once visualized in the Web Mercator view, the shapes become distorted, especially near the poles.

I've tried projecting them onto Web Mercator, but this hasn't resolved the issue. Also, snapping the coordinate system to an empty shapefile without a coordinate system and then redefining it didn't work either. Does anyone have any tips or suggestions for this problem?

Thanks in advance for your help!

WGS 1984 with the right geometrie (see how the Shape starts from the single Points)

WGS 1984 Web Mercator (the Shape changes and doesnt starts from the single points. its slightly off

danretired · Answer

If your points are in decimal degrees, then you buffer them using the geodesic option.  I assume you are using a planar buffer size (eg meters, feet etc)

You aren't going to get circles in any event in web mercator

Tissot's indicatrix - Wikipedia

TrutzBongartz · Answer

Thanks for your reply!

To begin with, unfortunately, the shapes must ultimately be in the WGS 1984 Web Mercator coordinate system. There is no way around this. If I understand you correctly, I need to ensure that the original buffers on which the shapes shown in the figure are based are generated geodetically? These could then be correctly converted to WGS Web Mercator after the displacement process within the Python code?

danretired · Answer

It might be best to use a projected coordinate system appropriate for your E-W coverage, then produce the buffers using the geodesic method

if yoi were you using the geodesic option and giving it a planar distance?

Buffer (Analysis)—ArcGIS Pro | Documentation

How Buffer (Analysis) works—ArcGIS Pro | Documentation

the shape is expected