User talk:Wpjo

Due to the ellipsoid shape of the earth, the curvature of its surface is not the same. Based upon local curvature, an observer might conclude the circumference of the earth is in between 39800 and 40200 km (source http://en.wikipedia.org/wiki/Latitude#Geocentric_latitude). The curvature --and thus the refraction-- depend on the latitude and the direction in which refraction was measured. Please note that this background information is missing.

regards wpjo 19:21, 1 November 2013 (UTC)~