Spectra Precision Survey Pro v4.6 Recon and Nomad User Manual - Manual (Page 249)

GPS Overview
239
change appreciable within the range of RTK GPS, so this map
projection is an excellent way to model simple flat earth ground level
coordinate systems.
Ellipsoid Scale Factor
This scale factor accounts for the height of the ground above the
reference surface (the ellipsoid). This scale factor is defined
geometrically: Consider the following diagram:
R+h
Radius of
Ellipsoid, R
Ellipsoid
Height, h
Distance on
Ground
Distance on
Ellipsoid
dist
ground
/(R+h) = dist
elip
/R
dist
elip
/dist
ground
= R/(R+h)
k
elip
= R/ (R+h)
Combined Scale Factor
Generally, the two scale factors are multiplied together into a
combined scale factor. The combined scale factor is then applied to
grid distances to get ground distances:
k
cf
= k
elip
* k
map
dist
grid
= dist
ground
* k
cf
Fig. 5: Ellipsoid Scale Factor
The effect of height above the ellipsoid on scale.