depth test doesn't work

[iSpring]

Earth radius is 6378137. It is a big number. Bigger radius, less depth precision. It results in depth test issue.

[iSpring]

Updating EARTH_RADIUS from 6378137 to 14000 can fix this issue.

[iSpring]

z-fighting
https://learnopengl.com/#!Advanced-OpenGL/Depth-testing

[iSpring]

Z fighting & polygon offset
https://sites.google.com/site/threejstuts/home/polygon_offset