I am having a problem with a conversion I'll share that here. Who can help?
We have recieved some spatial data from Burundi. Therefore it has a geographic coordinate system. Unfortunately I am not able to convert it to WGS84. Whatever I try, there is always a shift in the geodata of several meters.
More details:
We are working in Esri ArcGIS 10.1. We also tried to convert the data with Quantum GIS. In both cases the results were not accurate. Extra information on our activities/settings: The transformation we used is an international standard: http://georepository.com/transformation_3998/Arc-1960-to-WGS-84-4.html The specifications of this transformation is the same as of Arc 1950 to WGS 1984 number 3. Quantum GIS and Esri ArcGIS are telling us that the projection of the data is "User Defined". The systems do not recognize the projection as a known projection system. > Quantum GIS: USER:100000 - * Auto generated CRS (+proj=tmerc +lat_0=0 +lon_0=30 +k=0.9996 +x_0=500000 +y_0=10000000 +a=6378249.145 +b=6356514.966398753 +towgs84=-143,-90,-294,0,0,0,0 +units=m +no_defs)
There isn't much information available for that part of the world. EPSG (http://www.epsg.org - I'm on the subcommittee that maintains it) thinks that the transformation, Arc 1950 to WGS 1984 (3) is incorrect. That Burundi data was on Arc 1960 instead. There's another transformation, Arc 1960 to WGS 1984 (4). You might try defining your data as Arc 1960 with the projection information you have and use that transformation.
None of the transformations that I know about in that area are very good.
Cliff Mugnier in his Grids & Datums column on Burundi lists a GK zone for Burundi that has a scale factor of 1.0, not 0.9996, so that's something else to try.
There isn't much information available for that part of the world. EPSG (http://www.epsg.org - I'm on the subcommittee that maintains it) thinks that the transformation, Arc 1950 to WGS 1984 (3) is incorrect. That Burundi data was on Arc 1960 instead. There's another transformation, Arc 1960 to WGS 1984 (4). You might try defining your data as Arc 1960 with the projection information you have and use that transformation.
None of the transformations that I know about in that area are very good.
Cliff Mugnier in his Grids & Datums column on Burundi lists a GK zone for Burundi that has a scale factor of 1.0, not 0.9996, so that's something else to try.
Melita
Thank you Melita for your quick reply! I will have a look at it and will let you know the outcome. Harmen
