Re: GeoDistance and transformation from WGS84 to WGS84

• To: mathgroup at smc.vnet.net
• Subject: [mg101559] Re: GeoDistance and transformation from WGS84 to WGS84
• From: ragfield <ragfield at gmail.com>
• Date: Fri, 10 Jul 2009 06:44:17 -0400 (EDT)
• References: <h340nr\$gjs\$1@smc.vnet.net>

```On Jul 9, 12:55 am, "Sjoerd C. de Vries" <sjoerd.c.devr... at gmail.com>
wrote:
> Anyone an idea why the following doesn't work? It calculates the
> distance between two points on the earth with given latlong
> coordinates. WGS84 is the datum used for GPS, if I'm not mistaken.
>
> In[86]:= GeoDistance[GeoPosition[{1, 0}, "WGS84"],  GeoPosition[{0,
> 0}, "WGS84"]]
>
> During evaluation of In[86]:= GeoDistance::datum: No direct
> transformation between datums "WGS84" and "WGS84" is available. >>
>
> Out[86]= GeoDistance[GeoPosition[{1, 0}, "WGS84"],
>  GeoPosition[{0, 0}, "WGS84"]]
>
> The "More Information" box of GeoPosition specifically states that
> WGS84 is one of the allowed datums. However, GeodesyData["Datum"] and
> GeodesyData["ReferenceEllipsoid"] make clear that WGS84 is not a
> datum, but a reference ellipsoid (WGS72 seems to be both).

I don't know *why* it doesn't work, but if you change WGS84 to
WGS84Original it does work:

In[255]:= GeoDistance[GeoPosition[{1, 0}, "WGS84Original"],
GeoPosition[{0, 0}, "WGS84Original"]]

Out[255]= 110574.

-Rob

```

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