[Proj] projection of Madagascar

OvV_HN ovv at hetnet.nl
Wed Apr 30 05:49:28 EDT 2008

Gerald I. Evenden wrote:
> Just to add to the confusion, libproj has always contained the +proj=labrd 
> projection based upon a development by John Snyder.  An example script would 
> be:
> PROJ="+proj=labrd +ellps=intl +azi=18d54 +lat_0=18d54S +lon_0=46d26'13.95E 
> +k_0=0.9995 +x_0=400000 +y_0=800000"
> Are there any known values known to be acceptable by Madagascar 
> surveyors/government?

The longitude of origin of 46d 26'13.95E puzzles me.
This value is given in the Madagascar Grids & Datums article by mr.
Mugnier, but he gives a value of 21G with respect to Paris, which would
be the same as 46d 26m 13.95s East of Greenwich (see column 2 on page 
144 of said article).
Hmmm... that would be a new chapter in cartography!

Anyhow, the EPSG GN 7-2 value of 46d 26m 14.025s wrt Greenwich is 
equivalent with exactly 49 grad wrt Paris. Wouldn't that be a more 
logical value?

Oscar van Vlijmen

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