[Proj] Unknown Datum

Kassiane Mentz kassimaiden at gmail.com
Thu Nov 25 09:52:08 EST 2010

Hi. Thanks for your answer, but I maybe you don't understood my problem.
How to use parameters convertion? And where insert the new Datum?
How I will use the +towgs84 parameters if the Proj4 didn't recognized my
datum's parameters?


2010/11/25 Jean-Claude Repetto <jrepetto at free.fr>

> Le 25/11/2010 14:25, Kassiane Mentz a écrit :
> > We are in a city in southern Brazil (Porto Alegre - Rio Grande do Sul),
> > and have a lot of maps that have a
> > unknown local Datum.
> > We are using an application that uses Mapserver webmapping but is having
> > trouble with our maps becouse
> > they were using an unknown datum, even our forecast and our ellipsoid
> > are known.
> > Trying to makem with the mapserver automatically convert our maps to
> > WGS84, which is what most
> > approached our features, we decided to insert a new proj4 Datum.
> > In file PJ_Datums.c we inserted a new reference vector in pj_datums []
> > for our datum, passing the parameters
> > conversion. Also insert an entry in the archive world for our specific
> > case.
> > Compiled the library with our modifications and uses MapServer to
> > perform a test. Using the command Shp2img, we realized that this stopped
> > working, which indicates that something happened in Proj4.
> > We would like to know if there really is a way to include a unknown
> > Datum to the proj4 perform the conversion.
> Hello,
> You don't need to change the PROJ.4 source code. Just use the +towgs84
> parameter to perform the datum transformation.
> Jean-Claude
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Kassiane S. Mentz
Microsoft Office Specialist
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