[OSGeo Africa] Reconstruction old SG diagrams

[Aslam Parker]

Hi Hanlie

The coordinates that you have attached are in a local system. There is no ways of transforming it without common points in the National Control Survey System.

You have a few choices:

If the farm/diagram has not consolidated and still exist, then the spatial data from the SG would be a good approximation (if you just need a rough idea).

If you need accurate coordinates, I would recommend you ask a Land Surveyor.

If you attempt to reconstruct this property more accurately, you will need common points in the NCSS and transform from a local system to the SA Coordinate system. However you have to know how to transform not only from local systems to national systems, but also from Cape Datum to Hartebeesthoek94.

I hope this assists 

-----Original Message-----
From: Africa [mailto:africa-bounces at lists.osgeo.org] On Behalf Of Hanlie Pretorius
Sent: Monday, February 20, 2017 9:24 AM
To: Africa local chapter discussions
Subject: [OSGeo Africa] Reconstruction old SG diagrams

Hi,

I was wondering if any surveyor on this list is willing to transform the local coordinates in the attached mid 20th century SG diagrams to WG25. They are all in the Mafikeng region and I can't use the current cadastre to locate them - too much has changed.

Thanks very much.

Regards
Hanlie