[OSGeo Africa] Using south-orientated CRSs for GIS in South Africa

Frank Sokolic sokolic at worldonline.co.za
Tue Aug 27 02:18:14 PDT 2013

ArcGIS 10+ and the soon-to-be-released QGIS 2.0 contain the (correct) 
south-orientated definitions of the Lo coordinate reference systems. 
However, the problem with this is that there is a HUGE amount of spatial 
data in SA and neighbouring countries that use a "north-facing" 
orientation. To convert all of this to the south-orientated system will 
have a massive impact on the GIS community both in terms of money and 
time. Can we afford this?

Does National Geo-spatial Information (NGI) have a policy on which CRS 
to use for GIS? They also supply spatial data using "north-orientated" 
coordinates so perhaps they have a policy somewhere that states:
- use south-orientated coordinates for survey data
- use north-orientated coordinates for GIS data?


On 26/08/2013 22:03, Gavin Fleming wrote:
> Very topical point Frank
> Now that EPSG and proj4 have codes and implementations for the
> south-facing LO/Hartebeesthoek94 system, it's all well and good except
> as you say most GIS practitioners use north-facing, which we should not
> call 'LO' at all. I wish EPSG had set up the north facing series instead.
> If you get coordinates from a surveyor they are likely to be
> south-facing, otherwise not, probably because GIS has not been able to
> handle south-facing till recently?
> In my early GIS days if we got south-facing data, we'd flip it to
> north-facing manually before continuing.
> There's a bit of a blocker in QGIS 1.9 at the moment where, if you
> define a north-facing LO CRS (which I prefer to call something like
> 'SouthAfricaTM19' instead of 'LO19'), it forces '+axis=wsu' into the
> definition, which makes it south-facing. I've filed a bug report [1]
> about this, hoping it gets fixed before 2.0 is released.
> I'm working in Lesotho now on parcel data which is in north facing TM
> (on the Cape datum still), though survey data comes in south-facing. The
> LO/Cape datum series is also in EPSG now, but also only as south-facing
> :-(.
> [1] http://hub.qgis.org/issues/8487
> Gavin
> On 26/08/2013 17:08, Frank Sokolic wrote:
>> Dear List,
>> As many of you know, the South African coordinate reference system is
>> defined as a south-orientated system, with Westings (Y) increasing
>> towards the south and Southings (X) increasing towards the West.
>> However, in a GIS context I've only ever seen SA CRSs (e.g. Lo19,
>> Lo31, etc) represented with x-coordinates increasing eastwards and
>> y-coordinates increasing northwards.
>> So, for example, the coordinates of the entrance to Durban harbour are
>> represented in Hartebeesthoek94/Lo31 as
>> Y = -5641.000
>> X = +3305647.886
>> but in practice in a GIS this point is represented as
>> X = +5641.000
>> Y = -3305647.886
>> My question is: are there any GIS practitioners in South Africa who
>> use the SA CRSs in the south-orientated sense?
>> Regards, Frank.
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