[Proj] Unknown Datum

Clifford J Mugnier cjmce at lsu.edu
Fri Nov 26 11:45:19 EST 2010

This is likely based on the Astro Position at Extremo Nordeste da Base de Leste 1904.
Clifford J. Mugnier, C.P., C.M.S.
Chief of Geodesy,
Center for GeoInformatics
Department of Civil Engineering 
Patrick F. Taylor Hall 3223A
Baton Rouge, LA  70803
Voice and Facsimile:  (225) 578-8536 [Academic] 
Voice and Facsimile:  (225) 578-4578 [Research] 
Cell: (225) 238-8975 [Academic & Research]
Honorary Life Member of the 
Louisiana Society of Professional Surveyors 
Fellow Emeritus of the ASPRS 
Member of the Americas Petroleum Survey Group


From: proj-bounces at lists.maptools.org on behalf of Kassiane Mentz
Sent: Thu 25-Nov-10 07:25
To: proj at lists.maptools.org
Subject: [Proj] Unknown Datum


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.

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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