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Posted by z.entropic on May 1, 2006, 10:52 pm


I'm asking because I do not know how to include the geoid shape
corrections to the standard geometrical formula for a sphere... A
MapSource section gives at N 42 20' a distance of ~103 km per 1deg15',
which is equivalent to 1373 m per 1 arc min, and I'm wandering what
kind of geoid correction I might see...

z.entropic


Posted by Sam Wormley on May 1, 2006, 11:45 pm


z.entropic wrote:
> I'm asking because I do not know how to include the geoid shape
> corrections to the standard geometrical formula for a sphere... A
> MapSource section gives at N 42 20' a distance of ~103 km per 1deg15',
> which is equivalent to 1373 m per 1 arc min, and I'm wandering what
> kind of geoid correction I might see...
>
> z.entropic
>

Since the geoid is irregular (and why would you want to calculate
distance along it in the first place?), why not use the WGS84
ellipsoid?

Aviation [Navigation] Formulary by Ed Williams
http://williams.best.vwh.net/avform.html


Posted by Tony on May 2, 2006, 10:05 pm


> Since the geoid is irregular (and why would you want to calculate
> distance along it in the first place?), why not use the WGS84 ellipsoid?

Thanks for the useful formulary--it's been a long time since I had to
deal with this stuff... Now, why? Because I didn't know better, but
wanted to know what's the distance equivalent to 1/1000 of an arc min
on my GPSR when I'm traveling straight East to Boston... <VBG>

z.entropic


Posted by sigurdhu on May 2, 2006, 2:00 pm


z=2Eentropic.

Your estimate is quite good, see
http://home.online.no/~sigurdhu/Grid_10min.htm

Latitude: 42=B0 20'
Distance to nearest pole:
2868.954 int. naut. miles
5313.303 kilometres
1 minute of lati=ADtude: 1851.329 metres
1 minute of longi=ADtude: 1373.616 metres
Circumference of parallel of latitude:
29670.107 kilometres
16020.576 int. naut. miles

------
Sigurd
N 59=B056' E 10=B042' (WGS 84)

Size and shape of the Earth (WGS 84)?
Garmin MapSource map sizes?
Garmin GPSmap 276C, GPS 12 MAP and GPS III (PLUS)?
See http://home.online.no/~sigurdhu


z=2Eentropic skrev:
> I'm asking because I do not know how to include the geoid shape
> corrections to the standard geometrical formula for a sphere...
> A MapSource section gives at N 42 20' a distance of ~103 km per 1deg15',
> which is equivalent to 1373 m per 1 arc min, and I'm wandering what
> kind of geoid correction I might see...
>=20
> z.entropic


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