The Rectified Skew Orthomorphic projection also known as Hotine Oblique Mercator, is used for the national topographic mapping coordinate system of Malaysia, while the Cassini projection is used for the state level Ordnance/Cadastral Survey. In preparing the State Structure Plan using GIS, the issue of different projections from the National Physical Plan data (using RSO for its base map) and cadastral data from the individual states, has raised considerable concern for standardisation. Cassini projection is a Transverse Mercator projection that is neither conformal nor equal-area.This projection was formerly used by the Ordnance Survey throughout the United Kingdom and is still being used in a few countries for instance Cyprus, Denmark, Germany,Trinidad and Tobago. This projection was developed by C.F Cassini in the 18th century and J.G von Soldner in the 19th century. RSO projection is an Oblique Mercator projection that is conformal but not equal area.This projection is being used as the national coordinate system of a few countries for instance Singapore and Borneo.This projection was developed in 1900-1950 by Rosenmund, Laborde, Hotine and others. llustrations of the two projections are as shown below: (http://exchange.manifold.net/ manifold/manuals/5_userman/)
Normal cylindrical equal-area projections
Transverse cylindrical equal-area projections
Oblique cylindrical equal-area projections
Is there any problem when dealing with these two projections? Maybe not - because of the number of projection converter software (or extensions) around. A case in point being the Malaysia RSO-Casslni Projection Converter, which is an ArcView extension written using Avenue development language.This extension enable the conversion between Rectified Skew Orthomorphic (RSO) and Cassini-Soldner which are currently used in Malaysia.They are as follows: 1. Malaysia RSO to State Cassini 2. State Cassini to Malaysia RSO (http://www.malaysiagis.com/tech_center/map_projection/)
RSO
Cassini
A lot more information on GIS can be found in the internet. Just type
‘GIS’ on any search engine, and select your
subject of interest. Happy Learning!
ISSUE 01 / VOL.02 / JUNE. 2004
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