[GIS] Identify coordinate system used near Kuala Lampur

coordinate systemcoordinateslatitude longitudemalaysia

I have some coordinates that were given to me, and I do not know much about how they were taken. I thought they were UTM coordinates, but when I try to convert them using some online tools I always obtain a value that is far away from the supposed point. That makes me think that they are not UTM coordinates, so I need some help to identify what system is used.

Here is an example coordinates data straight from the file I was provided, copied exactly as it was written. The positions are located in Kuala Lumpur, Malaysia, and were surveyed around 1997; I used 47N as UTM zone.

            Provided  Converted  
easting   106374.634   0.874278 latitude 
northing   96819.608  95.464439 longitude

(Converted is even out of the 47N zone!)

   Expected (approx)  converted in UTM
latitude    3.145241  easting  806771.55
longitude 101.759941  northing 348052.77

Any idea on what kind of coordinates are being used here?

Best Answer

Not the perfect solution, but might take you further:

Malaysia does not use UTM for surveying. The EPSG registry lists several projections valid for West Malaysia, and the Selangor state. You will find further information on malaysian CRS at

http://www.asprs.org/a/resources/grids/04-2009-malaysia.pdf

https://www.jupem.gov.my/wp-includes/files/pekeliling/PKPUP3-2009.pdf

http://eprints.utm.my/3527/1/gdm2000_DSMMKL.pdf

Unfortunately, none of them really fits to your data. So it may be useful to set up your own projection.

You have a reference point in WGS84 degrees (101.759941 East 3.145241 North) and local coordinates (106374.634 East 96819.608 North). Make sure they are in decimal degrees and meters.

For statewide surveying, Malaysia uses cassini projections, based on the GDM2000 geographic CRS. So we take the proj.4 definition of Selangor grid EPSG:3380:

+proj=cass +lat_0=3.68464905 +lon_0=101.3891079138889 +x_0=-34836.161 +y_0=56464.049 +ellps=GRS80 +units=m +no_defs

and replace the values of the origin with the known point you have:

+proj=cass +lat_0=3.145241 +lon_0=101.759941 +x_0=106374.634 +y_0=96819.608 +ellps=GRS80 +units=m +no_defs

You can use this custom projection string with PROJ.4 cs2cs, or all GDAL-based software. The reference point will be matched exactly, others may be offset, depending on the extent of your data.

If you compare a grid of this CRS (in red) with the Selangor grid (in green), you get this picture:

enter image description here

The Selangor grid has its true origin at some point in Kuala Lumpur (next to the Istana Budaya). Your grid has the crossing of 100000m almost on the same spot. So they have just added 100000 on both coordinates to prevent having negative and positive coordinates (a common practice in many surveying systems). So you can just subtract that value from your coordinates, and work with EPSG:3380.

If you are unsatisfied, you can try the old Kertau 1968 datum as well. EPSG:4393 Kertau 1968 / Selangor Grid would be suitable, but is not included in all GDAL packages.

+proj=cass +lat_0=3.680344444444444 +lon_0=101.5082444444444 +x_0=-21759.438 +y_0=55960.906 +a=6377304.063 +b=6356103.038993155 +towgs84=-11,851,5,0,0,0,0 +units=m +no_defs

The additional false easting and northing of 100000 meters would be the same, since the true origin is almost on the same spot in Kuala Lumpur as for GDM2000.

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