[Proj] Unknown Datum

Kassiane Mentz kassimaiden at gmail.com
Thu Nov 25 08:25:41 EST 2010


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
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.

The following parameters used:

Projection: Transverse Mercator

Ellipsoid: International 1909 (Hayford)

X Translation (m) -105.3687744788

Y Translation (m) 128.2533004372

Z Translation (m) 5.9501954062

X Rotation (seconds) 0.2526444267

Y Rotation (seconds) -4.9126506172

Z Rotation (seconds) -2.1177220547

Scaling factor 0.99998717166457

False East X 5,000,000 m

False North Y 200,000 m

PS.: We emphasize that we are just programmers, and we are working with
cartographers, who does not dominate the program.


Microsoft Office Specialist
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