LocalEarthRadius

MATLAB

[re,NSre,EWre] = LocalEarthRadius(G)
[re,NSre,EWre] = LocalEarthRadius(R1,[R2],[re])

Computes the effective spherical Earth radius as function of latitude.

Parameters	Description
G [struct]	Geometry structure from GeomStruct or a comma-separated list of (R1,[R2],[re])
R1 [Nx3 vector]	LLA position vector 1.
R2 [Nx3 vector]	(Optional) LLA position vector 2. Can be empty but must be passed if passing re. If not passed in or passed in as empty, re is (NSre+EWre)/2.
re [vector]	(Optional) 2 element vector, [Equatorial radius, Polar radius], of the geodetic earth radii (m). Defaults to [6378137, 6356752.314] from PhysicalConst.

Return Values	Description
re [vector]	Vector with same dimension as R1 & R2 with the effective spherical Earth radius (m).
NSre [vector]	Vector with same dimension as R1 & R2 with the effective North/South spherical Earth radius (m).
EWre [vector]	Vector with same dimension as R1 & R2 with the effective East/West spherical Earth radius (m).

D. H. Maling, Coordinate Systems and Map Projections, 2nd Edition Pergamon Press, 1992, pp.. 77-79.