Convert coordinates from Arc 1950 (EPSG:4209) to WGS 84 (EPSG:4326) — official EPSG transformation parameters, accuracy and area of use, with a free in-browser converter.
Arc 1950 (EPSG:4209) is the classical datum of south-central Africa, computed along the 30th-meridian arc triangulation on the Clarke 1880 (Arc) ellipsoid. It underlies older national mapping in Botswana, Zimbabwe, Zambia, Malawi and neighbouring countries.
EPSG publishes per-country transformations to WGS 84 with accuracies from a few metres to about 20 m — the network was vast, and each national fit absorbed different distortions. Pick the operation matching your country of interest.
Most of the region has since adopted ITRF-based national frames, but enormous volumes of mining, cadastral and topographic data remain on Arc 1950.
Try it: Victoria Falls, Zimbabwe
Input (EPSG:4209): 25.8572, -17.9243
The EPSG Geodetic Parameter Dataset defines 9 transformations between Arc 1950 (EPSG:4209) and WGS 84 (EPSG:4326). Each applies to a specific area — pick the one whose area of use covers your data.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -138 | metre |
| Y-axis translation(ty) | -105 | metre |
| Z-axis translation(tz) | -289 | metre |
Derived at 9 stations. Accuracy 3m, 5m and 3m in X, Y and Z axes.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -125 | metre |
| Y-axis translation(ty) | -108 | metre |
| Z-axis translation(tz) | -295 | metre |
Derived at 5 stations. Accuracy 3m, 3m and 8m in X, Y and Z axes. Note: Lesotho does not use Arc 1950 but does use Cape (CRS code 4222); Cape and Arc 1950 datums share a common fundamental point.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -142 | metre |
| Y-axis translation(ty) | -96 | metre |
| Z-axis translation(tz) | -293 | metre |
Derived at 10 stations. Accuracy 5m, 8m and 11m in X, Y and Z axes. Replaced by Arc 1950 to WGS 84 (10), tfm code 6906.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -145 | metre |
| Y-axis translation(ty) | -97 | metre |
| Z-axis translation(tz) | -292 | metre |
Derived at 38 stations. Accuracy 10m in each of X, Y and Z axes. Replaces Arc 1950 to WGS 84 (9), tfm code 1121.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -134 | metre |
| Y-axis translation(ty) | -105 | metre |
| Z-axis translation(tz) | -295 | metre |
Derived at 4 stations. Accuracy 15m in each axis. Note: Eswatini does not use Arc 1950 but does use Cape (CRS code 4222); Cape and Arc 1950 datums share a common fundamental point.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -161 | metre |
| Y-axis translation(ty) | -73 | metre |
| Z-axis translation(tz) | -317 | metre |
Derived at 6 stations. Accuracy 9m, 24m and 8m in X, Y and Z axes.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -179 | metre |
| Y-axis translation(ty) | -81 | metre |
| Z-axis translation(tz) | -314 | metre |
Derived at 7 stations. Accuracy 13m, 25m and 7m in X, Y and Z axes. Info source gives source CRS as Arc 1960. From inspection of parameter values, comparison with other CTs and geographic applicability of CRS, OGP believes that this should be Arc 1950.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -147 | metre |
| Y-axis translation(ty) | -74 | metre |
| Z-axis translation(tz) | -283 | metre |
Derived at 5 stations. Accuracy 21m, 21m and 27m in X, Y and Z axes.
| Parameter | Value | Unit |
|---|---|---|
| X-axis translation(tx) | -143 | metre |
| Y-axis translation(ty) | -90 | metre |
| Z-axis translation(tz) | -294 | metre |
Derived at 41 stations. Accuracy 20m, 33m and 20m in X, Y and Z axes. Note: Eswatini and Lesotho do not use Arc 1950 but do use Cape (CRS code 4222); Cape and Arc 1950 datums share a common fundamental point.
The same transformation with common GIS tools and libraries:
from pyproj import Transformer
transformer = Transformer.from_crs("EPSG:4209", "EPSG:4326", always_xy=True)
x, y = transformer.transform(-73.9857, 40.7484)
print(x, y)geographic system using latitude and longitude on an ellipsoid · Area of use: Africa - Botswana, Malawi, Zambia, Zimbabwe
+proj=longlat +a=6378249.145 +rf=293.4663077 +towgs84=-143,-90,-294,0,0,0,0 +no_defs +type=crsMore about EPSG:4209 →
geographic system using latitude and longitude on an ellipsoid · Area of use: World (by country)
+proj=longlat +datum=WGS84 +no_defs +type=crsMore about EPSG:4326 →