1

I am basic user of GIS. I have a project in Rwanda and have received CAD information in a coordinate system I am unaware of. In addition this isn't the first time I have come across similar references for similar areas. Can anyone work out the coordinate system from these coordinates:

  • decimal degrees -2.2710, 30.2612
  • unknown system 529041.54, 4748727.20
1
  • 1
    Probably the decimal degree are in WGS84, you can try to insert into google earth and check if they are in the right position.
    – Riflo
    Jan 10, 2020 at 13:15

1 Answer 1

5

I think I've found the coordinate system you're looking for. Your unknown coordinate reference system seems to be referred to in Rwanda as ITRF 2005 / TM Rwanda. It is a projected coordinate system using Transverse Mercator with the following parameters :

False Easting : 500,000
False Northing : 5,000,000
Central meridian : 30
Latitude of origin : 0
Scale factor : 0.9999
Linear unit : Meter
Geographic Coordinate System: GCS_ITRF_2005
Datum: D_ITRF_2005

The crs is mentioned in some ESRI Rwanda documents such as this one and is used by local government in some web services. The ESRI-style WKT for that crs is:

PROJCS["ITRF_2005",GEOGCS["GCS_ITRF_2005",DATUM["D_ITRF_2005",SPHEROID["GRS_1980",6378137.0,298.257222101]],PRIMEM["Greenwich",0.0],UNIT["Degree",0.0174532925199433]],PROJECTION["Transverse_Mercator"],PARAMETER["False_Easting",500000.0],PARAMETER["False_Northing",5000000.0],PARAMETER["Central_Meridian",30.0],PARAMETER["Scale_Factor",0.9999],PARAMETER["Latitude_Of_Origin",0.0],UNIT["Meter",1.0]]

And the proj4 string would be:

+proj=tmerc +lat_0=0 +lon_0=30 +k=0.9999 +x_0=500000 +y_0=5000000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

(Note: I did not use any transformation between ITRF2005 and WGS84)

With these assumptions, in decimal degrees, your example unknown point is located at lat,lon: -2.2726260, 30.2611137:

enter image description here

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.