[OSGeo Africa] SACRS 'south-oriented' clarification

Gavin Fleming gavin at afrispatial.co.za
Tue Sep 3 05:16:42 PDT 2013

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.



Gavin Fleming
t: 0218620670
c: 0845965680
f: 0866164820

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