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I have coordinates in *GPS (WGS84) (deg) format and I need convert them to South African Cape/Lo27 format. I know I can do this on this website (https://twcc.fr/en/#), but unfortunately I need to convert a few hundred coordinates, are there any conversion formulas that I can use?

Here is an example of my data:

What I have:

Longitude: -32.9220

Latitude: 27.7586

What I need:

X: -70991.542

Y: 3644059.052

Convergence: 0.4123

closed as too broad by PolyGeo Jan 31 '18 at 10:57

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    what software you want to use to display your GPS points? – LaughU Jan 31 '18 at 9:18
  • The end user (not me) is using arcgis – Inzane0047 Jan 31 '18 at 9:33
  • If you are after an algorithm/formula then perhaps review these Q&As: gis.stackexchange.com/questions/tagged/… – PolyGeo Jan 31 '18 at 10:57
  • I am pretty sure that your longitude and latitude values are swapped. – mkennedy Jan 31 '18 at 21:23
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For a simple batch conversion, you could use

https://mygeodata.cloud/cs2cs/

Copy & Paste your coordinate pairs and define the input CRS (4326, already the default setting) and output CRS (22287, as Marco mentioned). Also see this post.

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There are many ways to do it, but I am a QGIS fan, so my answer consider to load your coordinate in Qgis and then save them in the format you want using the appropiate epsg code, in your case EPSG:22287.

  • Unfortunately I am not familiar with QGIS, But it has become obvious that teaching myself how to use QGIS will benefit me greatly – Inzane0047 Jan 31 '18 at 9:40
  • No special skills, it is very user friendly! But I am assuming you know a bit of GIS to deal with your data. If not, I recomend some reading: A gentle gis introduction – Marco Jan 31 '18 at 9:45
  • Thanks! I have very limited knowledge of GIS, though I have worked on GE Smallworld and a bit on Arcgis. Currently I have QGIS installed and I am trying to learn it! – Inzane0047 Jan 31 '18 at 9:52
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To complete the task in ArcMap:

Just a note - Do Not Use ESRI's Default Lo27 Spatial Reference

Load all your points into Excel / A text editor. Make sure you have at least 3 columns. 1 - ID or Name for the point ; 2 - Latitude ; 3 - Longitude. Save the file and open ArcMap.

Add the data to ArcMap as you normally would, right click the file and select "Display XY Data". The next window that will pop up allows you to select the X Field (Your Longitude Column), the Y Field (The Latitude Column) and a Z Field - leave blank, unless you have a Z value. The next important thing is to select the "Edit" button. This will let you select the coordinate system for your GPS Points. You stated that you have the data in "WGS84".

enter image description here

On pressing edit, you will be taken to the "Spatial Reference Properties" page. From the window with all the folders, select "Geographic", "World" and then "WGS84". Press ok, and then Ok again from the "Display XY Data" Window. Below is just a screenshot of the Spatial Reference Window.

enter image description here

You data view should now show the points as a layer. THis layer is temporary, so if you close the MXD you will lose it. It will have the WGS84 Spatial Reference. You now need to re-project this data to the Cape Lo27 reference. To do this, open the ArcToolbox, Navigate to "Data Management Tools" then "Projections and Transformations" and the "Project" Toolbox. See below:

enter image description here

Select th einput as you XY Event Layer, Choose a filename to save the Event Layer a permanent Shapefile. Now select the little button to the right of the "Output Coordinate System" to make a new coordinate system for CAPE Lo27. A new window will pop up, it will be the "Spatial Reference Properties" again. This time select the drop down arrow from the little earth button - Shown in the pic below. Select "New" -> "Projected Coordinate System"

enter image description here

Things can get a little tricky here.

First: Choose a name for the new system you want to make: Cape_Lo31 Second: Choose the projection system you want to use: Select Transverse MErcator from the drop down list Third: Type 27 in space next to "Central Meridian" Fourth: Linear unit is "Meters" and the Meters per unit is "1" Fifth: Select "Change" in the Geographic Coordinate System

In this new window that pops up, scroll to the top, choose the "Geographic Coordinate Systems" folder, then "Africa" and search for "Cape". Select it.

enter image description here

Press ok, and finish running the "Project" Tool. In the data view there will now be a point file, correctly projected in Cape Lo27.

To show the coordinates in the attribute table you need to change the Data Frame Property's Coordinate System to the new Lo27 system you have created. Right click the "Layers" at the top of the Table of Contents, Select Coordinate System from the tabs and you will see your new system under the "Layers" folder. Select it and then open the attribute table in your new point file.

Add two new fields "X_lo27" and "Y_lo27". Right click on the field and select "Calculate Geometry". For the X field, select the X Coordinate and for the Y field select Y.

When this process has run you can export this attribute file out into text for use in any other software you need to.

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