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<div class="moz-cite-prefix"><font face="Times New Roman">For years
I have been working in GIS with a south orientated system.</font>
I don't understand what the problem is.<br>
<pre class="moz-signature" cols="72">Peter Newmarch
Professional Land Surveyor
4Y GeoInformatics Pty Ltd
Tel : +27 31 5642856
Fax : +27 31 5643074
Mobile : +27 82 5705859
eMail : <a class="moz-txt-link-abbreviated" href="mailto:newmarch@land-surveyors.com">newmarch@land-surveyors.com</a> </pre>
On 2013/08/27 02:07 PM, Frank Sokolic wrote:<br>
</div>
<blockquote cite="mid:521C9694.3080708@worldonline.co.za"
type="cite">Hi Aslam,
<br>
<br>
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?
<br>
<br>
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?
<br>
<br>
Frank.
<br>
<br>
<br>
On 27/08/2013 12:46, Aslam Parker wrote:
<br>
<blockquote type="cite">Hi All
<br>
Can we please not call it the Lo system, it is the South African
<br>
Coordinate Reference System. For a detailed and authoratative
definition
<br>
and explanation, please download
<br>
<a class="moz-txt-link-freetext" href="http://www.eepublishers.co.za/images/upload/positionit_2012/SA%20Coordinate%20reference%20system%20part1+2.pdf">http://www.eepublishers.co.za/images/upload/positionit_2012/SA%20Coordinate%20reference%20system%20part1+2.pdf</a>
<br>
Apparently ESRI has recently implemented the south oriented
SACRS in
<br>
their software.
<br>
<br>
<br>
Aslam Parker | Director: Geo-spatial Information and
Professional Support
<br>
<br>
|Chief Directorate: National Geo-spatial Information
<a class="moz-txt-link-abbreviated" href="http://www.ngi.gov.za">www.ngi.gov.za</a>
<br>
<a class="moz-txt-link-rfc2396E" href="http://www.ngi.gov.za/"><http://www.ngi.gov.za/></a>|Cape Town|
<br>
<br>
Tel +27 21 658 4302|Fax +27 86 211 7919| Mobile 082 331 8501|
<br>
<a class="moz-txt-link-abbreviated" href="mailto:aparker@ruraldevelopment.gov.za">aparker@ruraldevelopment.gov.za</a>
<a class="moz-txt-link-rfc2396E" href="mailto:aparker@ruraldevelopment.gov.za"><mailto:aparker@ruraldevelopment.gov.za></a>__
<br>
<br>
__
<br>
<br>
__
<br>
<br>
PPlease consider the environment before printing this email
and/or any
<br>
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<br>
<br>
>>> Peter Newmarch <a class="moz-txt-link-rfc2396E" href="mailto:newmarch@land-surveyors.com"><newmarch@land-surveyors.com></a>
8/27/2013 11:42 AM >>>
<br>
If one is producing maps in a country, then its common practice
to use
<br>
the national mapping system of that country. So I guess NGI does
have a
<br>
policy in the sense that their is a national mapping system for
all data
<br>
- which is the current Lo system.
<br>
<br>
Peter
<br>
<br>
Peter Newmarch
<br>
Professional Land Surveyor
<br>
4Y GeoInformatics Pty Ltd
<br>
Tel : +27 31 5642856
<br>
Fax : +27 31 5643074
<br>
Mobile : +27 82 5705859
<br>
eMail :newmarch@land-surveyors.com
<br>
<br>
On 2013/08/27 11:18 AM, Frank Sokolic wrote:
<br>
<blockquote type="cite">ArcGIS 10+ and the soon-to-be-released
QGIS 2.0 contain the (correct)
<br>
south-orientated definitions of the Lo coordinate reference
systems.
<br>
However, the problem with this is that there is a HUGE amount
of
<br>
spatial data in SA and neighbouring countries that use a
<br>
"north-facing" orientation. To convert all of this to the
<br>
south-orientated system will have a massive impact on the GIS
<br>
community both in terms of money and time. Can we afford this?
<br>
<br>
Does National Geo-spatial Information (NGI) have a policy on
which CRS
<br>
to use for GIS? They also supply spatial data using
"north-orientated"
<br>
coordinates so perhaps they have a policy somewhere that
states:
<br>
- use south-orientated coordinates for survey data
<br>
- use north-orientated coordinates for GIS data?
<br>
<br>
Frank.
<br>
<br>
On 26/08/2013 22:03, Gavin Fleming wrote:
<br>
<blockquote type="cite">Very topical point Frank
<br>
<br>
Now that EPSG and proj4 have codes and implementations for
the
<br>
south-facing LO/Hartebeesthoek94 system, it's all well and
good except
<br>
as you say most GIS practitioners use north-facing, which we
should not
<br>
call 'LO' at all. I wish EPSG had set up the north facing
series
<br>
instead.
<br>
<br>
If you get coordinates from a surveyor they are likely to be
<br>
south-facing, otherwise not, probably because GIS has not
been able to
<br>
handle south-facing till recently?
<br>
<br>
In my early GIS days if we got south-facing data, we'd flip
it to
<br>
north-facing manually before continuing.
<br>
<br>
There's a bit of a blocker in QGIS 1.9 at the moment where,
if you
<br>
define a north-facing LO CRS (which I prefer to call
something like
<br>
'SouthAfricaTM19' instead of 'LO19'), it forces '+axis=wsu'
into the
<br>
definition, which makes it south-facing. I've filed a bug
report [1]
<br>
about this, hoping it gets fixed before 2.0 is released.
<br>
<br>
I'm working in Lesotho now on parcel data which is in north
facing TM
<br>
(on the Cape datum still), though survey data comes in
south-facing. The
<br>
LO/Cape datum series is also in EPSG now, but also only as
south-facing
<br>
:-(.
<br>
<br>
[1] <a class="moz-txt-link-freetext" href="http://hub.qgis.org/issues/8487">http://hub.qgis.org/issues/8487</a>
<br>
<br>
Gavin
<br>
<br>
On 26/08/2013 17:08, Frank Sokolic wrote:
<br>
<blockquote type="cite">Dear List,
<br>
<br>
As many of you know, the South African coordinate
reference system is
<br>
defined as a south-orientated system, with Westings (Y)
increasing
<br>
towards the south and Southings (X) increasing towards the
West.
<br>
However, in a GIS context I've only ever seen SA CRSs
(e.g. Lo19,
<br>
Lo31, etc) represented with x-coordinates increasing
eastwards and
<br>
y-coordinates increasing northwards.
<br>
<br>
So, for example, the coordinates of the entrance to Durban
harbour are
<br>
represented in Hartebeesthoek94/Lo31 as
<br>
Y = -5641.000
<br>
X = +3305647.886
<br>
but in practice in a GIS this point is represented as
<br>
X = +5641.000
<br>
Y = -3305647.886
<br>
<br>
My question is: are there any GIS practitioners in South
Africa who
<br>
use the SA CRSs in the south-orientated sense?
<br>
<br>
Regards, Frank.
<br>
<br>
<br>
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