[OSGeo Africa] Using south-orientated CRSs for GIS in South Africa
sokolic at worldonline.co.za
Tue Aug 27 05:07:48 PDT 2013
What is NGI's position on GIS data? When I've obtained GIS data from NGI
in the past it has always been supplied as north-oriented, and not in
the south-oriented SA CRS. Was this because in the past there weren't
any GIS packages that supported the south-oriented SACRS?
Now that GIS programs are starting to support the SACRS (e.g. QGIS 2.0,
ArcGIS) does this mean that NGI will start distributing GIS data in the
On 27/08/2013 12:46, Aslam Parker wrote:
> Hi All
> Can we please not call it the Lo system, it is the South African
> Coordinate Reference System. For a detailed and authoratative definition
> and explanation, please download
> Apparently ESRI has recently implemented the south oriented SACRS in
> their software.
> Aslam Parker | Director: Geo-spatial Information and Professional Support
> |Chief Directorate: National Geo-spatial Information www.ngi.gov.za
> <http://www.ngi.gov.za/>|Cape Town|
> Tel +27 21 658 4302|Fax +27 86 211 7919| Mobile 082 331 8501|
> aparker at ruraldevelopment.gov.za <mailto:aparker at ruraldevelopment.gov.za>__
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> >>> Peter Newmarch <newmarch at land-surveyors.com> 8/27/2013 11:42 AM >>>
> If one is producing maps in a country, then its common practice to use
> the national mapping system of that country. So I guess NGI does have a
> policy in the sense that their is a national mapping system for all data
> - which is the current Lo system.
> 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 2013/08/27 11:18 AM, Frank Sokolic wrote:
>> 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
>>> 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 
>>> 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
>>>  http://hub.qgis.org/issues/8487
>>> 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.
>>>> Africa mailing list
>>>> Africa at lists.osgeo.org
>> Africa mailing list
>> Africa at lists.osgeo.org
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