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

Tue Aug 27 08:30:19 PDT 2013

For years I have been working in GIS with a south orientated system. I 
don't understand what the problem is.

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 02:07 PM, Frank Sokolic wrote:
> Hi Aslam,
>
> 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 correct orientation?
>
> Frank.
>
>
> 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
>> http://www.eepublishers.co.za/images/upload/positionit_2012/SA%20Coordinate%20reference%20system%20part1+2.pdf 
>>
>> 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>__
>>
>> __
>>
>> __
>>
>> PPlease consider the environment before printing this email and/or any
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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
>>
>> 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?
>>>
>>> Frank.
>>>
>>> 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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>>>>> Africa at lists.osgeo.org
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>>>>
>>>>
>>>
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