Re: [OpenMap Users] Constants in Geo.java

Hi Todd,

The code references
http://www.gfy.ku.dk/%7Eiag/HB2000/part4/groten.htm, which lists these
numbers as

Equatorial radius of the Reference Ellipsoid (mean equatorial radius of
the Earth) in the zero-frequency tide system (Bursa et al. 1998)
(6378.13662 KM)

and

Polar flattening computed in the zero-frequency tide system, (adopted
GM, w , and J2 in the zero-frequency tide system) (298.25642).

Seems like this is a different datum than WGS 84 and my impression is
that these should be changed in the OpenMap Geo class to match WGS 84,
or at least be settable.

Ken, comments? I just don't know the background of your choosing those
values.

- Don

On May 12, 2004, at 3:53 PM, Webb, Todd wrote:

> I am trying to track down some discrepancies between calculations in
> our mapping framework and OpenMap. For coordinate calculations there
> are some constants defined in Geo.java for Ellipsoid semi-major axis
> and flattening reciprocal. These numbers differ slightly from WGS84,
> does anyone know where they came from?
>
> WGS84 values: 6378137.0 m, 1/f=298.257223563
> Geo.java: 6378.13662 km, 1/f=298.25642
>
> Thanks,
> Todd
>
> Todd A Webb <twebb@titan.com>
> The Titan Corporation
> 3033 Science Park Road
> San Diego, CA 92121
> 858.597.9128
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Don Dietrick, dietrick@bbn.com
BBN Technologies, Cambridge, MA
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