I have drawn a circle on google earth pro in such a way that its radius starts from earth center 0,0 (lat/long) and ends at 0,90 (lat/long). This circle divide the earth into two equall halfs as shown in image. It is in line shape of length 39,999 km.

enter image description here

Then I have converted this circle in ArcGIS format and visualize there, it seem to be in a rectangle shape, obviously due to projection . When I select web mercator or other projected coordinate system of world they all give too much length as compared to its actual length 39,999 km.

enter image description here

My questions are:

  1. What method or suitable projection should I adopt in order to calculate its length on ArcMap?
  2. Length of this circle on google earth is 39,999 km which is different from the earth circumference which is about 40,075 km, why?
  • 1
    in this direction, it should be an ellipse, not a circle, because the Earth is flattened. It is approximatively 40008 km – radouxju Aug 28 '15 at 12:02
  • In ArcGIS as a complete line, I can only think of Stereographic, which displays half the world, centered on 0,0 (or anywhere on the equator), but then you'd have to measure the perimeter somehow...using a geodesic method. Or transverse Mercator, other cylindrical projections and treat it as two lines. – mkennedy Aug 28 '15 at 16:06
  • I have tried this method but this give too much length, but when I use measure tool for this rectangle shape on WGS 1984 projection it give a result of around 40,000 km which is acceptable. – Ghori Aug 29 '15 at 5:55

For #2 - 40,075 km is the East-West circumference. 40,008 km is the North-South circumference. The 9 km error in Google Earth's estimate could be the way they calculate great circle lengths.

  • Do you know what are the semi major and minor axis length of google earth reference system? – Ghori Aug 29 '15 at 5:50
  • It uses the WGS84 ellipsoid: epsg.io/7030-ellipsoid – Mintx Aug 31 '15 at 20:29

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