A collaborative piece by Li Shuen and Zoe Lum
Don't know the appropriate Universal Transverse Mercator (UTM) Zone for projecting your spatial data (i.e WGS). Download the above Google Earth KMZ with UTM zones https://www.dropbox.com/s/xvstuqe0qioq09u/utmzone.kmz?dl=0.
If you work in Malaysia you would use the following:
Peninsula Malaysia
West coast Zone 47 and East Coast Zone 48
East Malaysia
West - Zone 49 and East - Zone 50
For further information see this great website with the original download link https://en.geofumadas.com/Download-zones-utm-google-earth/
RSO
"ArcGIS has a CRS called Kertau RSO Malaya (m) as well as one called Kertau (RSO) RSO Malaya (m). I hope you spotted the difference! Very similar names for two different things. The second one ("(RSO) RSO") conforms to EPSG 3168. The first one does not: it has a different datum, a different ellipsoid, a different azimuth, and a different false easting; it doesn't conform to anything. (Thanks to Chee Pheng and the folks at WCS Malaysia for checking on this.)
If you are using ArcGIS, be really careful which of these you are using: look for (RSO) RSO in the name. You can check a shapefile by opening the *.prj file in a text editor (eg, Notepad) and looking at the start of the WKT:
+ PROJCS["Kertau_RSO_RSO_Malaya"... good.
+ PROJCS["Kertau_RSO_Malaya_Meters"... bad!"
Data appears misaligned after projecting to Kertau_RSO_RSO_Malaya or UTM Zone 47/48N
If your map appears "shifted" or misaligned even after trying both CRSs above, you might be working with data that is using the coordinate system "Malaysia Primary Geodetic Network 2000 " and the datum, "Geodetic Datum of Malaysia 2000" or GDM 2000 (2009).
This can occur especially with data acquired from JUPEM (Department of Survey and Mapping Malaysia); GDM 2000 is one of the more recent datums they are currently using.
Source: JUPEM, 2009
To project GDM 2000 (spheroid) to a 2D plane, we should use the projection Geocentric MRSO (Malayan rectified skew orthomorphic), for Peninsular Malaysia, and Geocentric BRSO (Borneo rectified skew orthomorphic) for East Malaysia.
Source: JUPEM, 2009
Why not Geocentric Cassini-Soldner?
The Geocentric Cassini projection is usually used for cadastral surveying purposes. This system has the advantage of reducing scale distortion. However for larger area, for example covering a state, the magnitude of the distortion is too great. Not to be advised for state wide study areas.
For more info on coordinate reference systems and projections in Malaysia and the methods of converting from one system to another, here's a technical guide published by JUPEM: https://www.jupem.gov.my/jupem18a/assets/uploads/files/pekeliling/e6846-pkpup3-2009.pdf.
To find out how and why the GDM 2000 was implemented in Malaysia, read: http://eprints.utm.my/id/eprint/3527/1/gdm2000_DSMMKL.pdf