[OSGeo Africa] SACRS 'south-oriented' clarification

Peter Newmarch newmarch at land-surveyors.com
Tue Sep 3 05:27:16 PDT 2013

The normal convention for surveyors is "name,y,x". - which will be 1c.

However, that being said, the nature of the coordinate is such that one 
can always tell which is the Y and which is the X.

Peter Newmarch
Professional Land Surveyor
4Y GeoInformatics Pty Ltd
Tel       : +27 31 5642856
Fax       : +27 31 5643074
Mobile    : +27 82 5705859
eMail     : newmarch at land-surveyors.com

On 2013/09/03 02:16 PM, Gavin Fleming wrote:
> Hi all
> We are adding some predefined north-oriented SACRS definitions to QGIS 
> so that we can all easily use the normal "LO" GIS data and not have to 
> 'roll our own' custom CRS definitions, which should make everyone's 
> lives easier.
> The proj4 South-oriented (TMSO) definitions from the EPSG that are in 
> QGIS 2 (all the 'Lo' Hartebeesthoek and Cape ones) are correct 
> according to the EPSG but I would like to establish whether everyone 
> follows the EPSG axis-order convention in South Africa. If the norm is 
> to NOT follow the axis order conventions, then the proj4 definitions 
> need to be altered.
> 1. Look at the alternatives for the point below. Say whether you 
> consider c or d to represent how you obtain and use TMSO coordinates:
> a. Here is a WKT point in EPSG:4326
> POINT(23 -28)    Axis order is x,y
> b. This is the same point in what we GIS users in SA would call 
> colloquially 'LO23' (i.e. north facing SACRS)
> POINT(-0.0000000003128453 -3098441.7473872434347868)   Axis order is x,y
> c. This is the same point in EPSG:2050 (SACRS) with EPSG axis-order 
> convention (y,x)
> POINT(0.0000000003128453 3098441.7473872434347868)   Axis order is y,x
> d. This is the same point in EPSG:2050 (SACRS) with what I think is 
> South African axis-order convention (x,y)
> POINT(3098441.7473872434347868 0.0000000003128453)   Axis order is x,y
> 2. Can anyone tell me what axis order ArcGIS expects TMSO coordinates 
> to be in?
> 3. Please send a small sample of data that you *know* is in TMSO. e.g. 
> some raw land surveyors data.
> If you've read this far I'd be grateful for a quick response to 1, 2 
> and 3.

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