Monday, May 30, 2011

Convert between GDM2000 and Peninsular Malaysian States Cassini coordinates using this Google gadget

Note: This Google Gadget no longer works as Google no longer supports Gadgets on web sites. A WebApp version is available on this site http://dominoc925-pages.appspot.com/webapp/gdm2000cassini/default.html.

GDM2000 or Geodetic Datum of Malaysia 2000 and Cassini-Soldner are coordinate systems commonly used in the Peninsular Malaysia States of Johor, Negri Sembilan, Melaka, Pahang, Selangor, Terengganu, Penang/Seberang Perai, Kedah, Perlis, Perak and Kelantam. This Google Gadget will allow you to convert between one or more pairs of State Cassini easting, northing coordinates and geographical GDM2000 latitude, longitude (GRS80) coordinates, all on GRS80 ellipsoid. It is possible to enter your own Cassini-Soldner projection parameters.

To convert easting,northing to latitude,longitude
  1. Select the Main tab (if it is not active)
  2. Type in one or more easting and northing coordinates in the Easting, northing text box, e.g. 8813.252,-23740.096.
  3. Click the Convert to Latitude,Longitude button (black pointing downward triangle).
To convert latitude,longitude to easting,northing
  1. Select the Main tab (if it is not active)
  2. Type in one or more latitude and longitude coordinates in the Latitude,northing text box e.g. 1:49:39.95355,103:38:24.93554.
  3. Click the Convert to Easting,Northing button (black pointing upward triangle)

To change the State Parameters
  1. Select the Prefs tab.
  2. Select the Use Cassini Parameters drop down list and choose a Peninsular Malaysian state e.g. Johor.

    The selected State's Cassini-Soldner parameters will be used for the conversion .

    Note: if you want to enter your own parameters, choose User-defined and type in the origin parameters

To change the coordinates delimiter character
  1. Select the Prefs tab.
  2. Select the Delimiter character drop down list and choose a character e.g. comma.

    The selected character will be the delimiter for your new key in coordinates and destination coordinates .
To change the latitude,longitude coordinate format
  1. Select the Prefs tab.
  2. Select the Latitude, longitude format drop down list and choose a format e.g. D:M:S.

    The selected format will be the format for your new key in latitude,longitude coordinates or the destination latitude,longitude coordinates.

14 comments:

Hilmy said...

Hi,

Just came across this post whilst doing some googling on GDM2000. Very interesting gadget you have there.

Some comments:
1. I assume you are using the GDM2000 parameters as published by EPSG (eg EPSG:3168 for Perak). These have non-zero easting, northing offsets. At some point (after August 2003), the Survey Dept (JUPEM)in Malaysia zeroed out all the state offsets. (I was trying to find out when this happened).
2. The zero-offset GDM2000 does not have EPSG entries but this is still denoted as GDM2000 by JUPEM.
3. The state Cassini origins have changed slightly due to the earthquakes in Indonesia. This is reflected in GDM2000 (2009).
4. You did not state the coordinate system for your lat/long. According to my test, this appears to be GDM2000 lat/long which most people assume to be identical to WGS84. There is a slight difference according to JUPEM.

So it would be most useful if you could state the references you used.

Thanks and regards.

Hilmy

d0min0c said...

Hi Hilmy
I am using the GDM2000 parameters as published by JUPEM in their Technical Manual on the Geocentric Datum of Malaysia (GDM2000) dated Aug 2003. If the State Cassini origins have changed since the Tsunami then I will have to look for the new parameters and update the gadget. And yes, the lat/long coordinate system is GDM2000.
thanks

d0min0c said...

The gadget has been updated to use GDM2000(2009) origins.

Troy Diack said...

Well done, very helpful. Can you list the calculations, would be a lot easier to plug into excel. For a sheet with numerous entries.

Troy Diack said...

Well done dominoc925, this is very helpful. I was wondering if you could post the calculation for the conversion.

dominoc said...

Hi Troy, it's just the standard Cassini-Soldner projection calculation published on the Internet. This is one place http://www.scribd.com/doc/47407155/PKPUP3-2009

Troy Diack said...

Right, right, I realised that after I had posted, thought it was a cassini to wgs conversion, would have been epic. I've noticed a slight difference in the wgs84 and gdm penang, but at least it fits. Anyways really enjoy your blog, are you located in Malaysia? If so maybe a cuppa teh tarih one evening.

Heng Malacca said...

May I know if GDM2000 and Cassini-Soldner are the same or two different coordinate systems?

I was provided with xyz data (offshore of Mersing - Pulau Besar and Pulau Pemanggil) where the xy data are in Cassini-Soldner coordinate system. I will need to convert the Cassini-Soldner coordinates into UTM-48.

Can you advise please?

dominoc925 said...

@Malacca,
GDM is a geodetic datum while Cassini Soldner is a projection referencing the datum. Taken together, they can be considered a "coordinate system".

Typically, to convert to UTM zone 48, Cassini-Soldner xy can be converted first to geographic lat,lon and then to UTM 48. A datum conversion may be needed since UTM 48 typically uses WGS84 datum.

Heng Malacca said...

Thank you, dominoc925, for the explanation.

Alvin Loh said...

Is there a way to convert google earth co ordinates (WGS 84) to GDM 2000? Many thanks

Awang said...

May I know if the rso and gdm is the same coordinate system? If they are different, what is their different?

dominoc925 said...

@Awang, RSO and GDM are different. RSO is a projection while GDM is a datum. Together they make up a coordinate system.

Omar Farouq said...

Hi, can I ask you a favor. I'm looking for a formula on how to do projection from GDM2000 to RSO Geocentric. I was given a task to manually calculate on the projection. So, Ineed detail on every calculation. I'm looking forward for an answer. Thanks in advance =)

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