Vertica Place creates circle-like polygons with vertices not equidistant to the center

Vivian_Rossi

Hello, I'm in the need to design a solution that requires precision on geometrical/geographycal operations.

Creating a circle I realized that the resulting polygon has vertices with distance to the center with an average of 15% less of the correct value with a peak of 30%.
Also the circle area value is different to the value I expected (217km2 vs 314km2)

 

I'm using the following statement to create a circle around a geo position with a radius of 10km:
select st_astext(st_buffer(ST_GeomFromText('POINT(9.0004 45.9997)'),0.09));
considering 1 degree = 111111 meter (as simple as earth circumference divided by 360)

Find attached the completed analysis.

Anyone can tell me what is wrong in my analysis?

Thanks in advance,
Vivian.

VirtualElvis

Sounds like curvature of the earth is at play here.

Vivian_Rossi

I've done some more tests, ST_Buffer works fine.

Workaround for me will be to use geometries instead of geographies.

Any other experiences are welcome, thanks!

Vivian.