I have a point dataset: a single point whose coordinates are geographic (WGS_1984). The coordinates of the frame containing this layer are Web Mercator (Auxiliary Sphere). Using ArcGIS basic 10.8.1

I used the **multiple ring buffer** tool to create a single buffer of radius 1 mile. The tool runs and draws a circle.

When I use the distance measuring widget to measure that radius it reports that the radius is 1.3 miles!

I use the **project tool** to convert the coordinate of my single point layer to those of the frame (Web Mercator Auxiliary sphere). Use again the **multiple ring buffer** tool. This time the circle drawn is indeed much smaller, and the distance widget confirms that the radius is indeed 1 mile.

OK. So you are going to tell me that I should not use that tool (and very possible other proximity tools) on a layer whose coordinate are geographic. Fine. But why does the tool not report this as an error? It know the coordinate systems of the frame and of the point layer. And how can the discrepancy be 30%? A one mile radius drawn on the tangent plane at a point on a sphere cannot possible differ from a one mile radius drawn on the sphere by as much as 30% - not when the radius of the earth is 4000 miles.

It is only by shear luck that I realised I had a problem. Why is the software unable to alert me to this problem?