[OSRS-PROJ] da, df

Gerald I. Evenden vze2hc4d at verizon.net
Sat Aug 4 20:19:07 EDT 2001

Remarkable.  The lengths some will go to to save such a trivial number of bytes.

I used to do this back in the 60's when memory was dear, but now???

"Felipe G. Nievinski" wrote:

> FYI (about the DA and DF parameters)
> The DA and DF are the delta values between the ellipsoid used by WGS-84 and another given ellipsoid:
> da = [a(WGS 84 ellipsoid) - a(second ellipsoid)] | a = semi-major (equatorial) axis
> df = [f(WGS 84 ellipsoid) - f(second ellisoid)*10000] | f = flattening
> They are commonly used by NAVSTAR-GPS receivers, which shall already know the WGS-84 model, and therefore needs less space to store just the delta values for the others Earth models than the a and f values themselves.
> For example, the Finnish ellipsoid can be defined by:
> da = -251 m
> df = -0.14192702


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