[postgis-users] Transform SAD69 to WGS84

[marco vieira]

Felipe:
 Try to convert using +towgs parameter and be careful with the various
realizations of SAD-69 in Brazil. If you want to convert back to WGS84 from
SAD-69 coordinates taked from GPS software (original in WGS-84 and converted
to SAD-69 by GPS software) you shall use the same parameters of GPS software
(maybe a mean value: -57 +/- 15,+1 +/- 6, -41 +/- 5); If you want to convert
with oficial (legal) parameters (IBGE) you take care about the "year of
realization".
 Take a look at
http://www.ibge.gov.br/home/geociencias/geodesia/param_transf/default_param_transf.shtm?c=19to
portuguese explanations about the parameters and
ftp://geoftp.ibge.gov.br/documentos/geodesia/pmrg/legislacao/RPR_01_25fev2005.pdf
to legislation.
 PostGis doesn't have +towgs described on proj4 parameter of 4291 srid.
Regards

-- 
Marco Vieira
+55 21 9499-6800
e-mail: maovieira at gmail.com

2006/12/5, Felipe Costa <fsc7mail at gmail.com>:
>
> Hello,
>
> I'm trying to transform a geometry in SAD69 (srid 4291) to WGS84 (4326).
> The problem which occurs is an error
>
> ERRO:  transform: couldn't project point: -45 (geocentric transformation
> missing z or ellps)
>
> I've looked for a possible solution of this problem and I saw someone with
> the same problem at
> http://postgis.refractions.net/pipermail/postgis-users/2006-October/013565.html
>
> And he found a solution at
> http://postgis.refractions.net/pipermail/postgis-users/2006-October/013570.html
>
> He discovered the variables of datum conversion for Belgian national grid
> which is 31370, but I have no idea what should I do to know this variables
> to my SAD69 system since my attribute proj4text in spatial_ref_sys has no
> mention to the variable towgs84.
> Can someone help me to discover how can I make this conversion?
>
> Thanks in advance,
>
> Felipe Costa
> SIGLAB - INPA
> Manaus - AM - Brazil
>
> _______________________________________________
> postgis-users mailing list
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/postgis-users/attachments/20061205/664e2961/attachment.html>