African Geomatics
Namibian Map Systems
A practical reference to Namibia's coordinate reference systems, map projections, datum transformations and vertical datum.
New Namibian Map System
The current reference datum for new maps in Namibia is the World Geodetic System 1984 (WGS84).
The specifications are set out in Government Gazette No. 6145, 7 October 2016 .
Section 8.1.3 specifies WGS84 as the horizontal datum for all new digital orthoimagery and vector data. Section 8.2.2 specifies a modified Transverse Mercator projection.
Projection Parameters
| Projection | Transverse Mercator |
|---|---|
| Central Meridian | 17° E |
| Latitude of Origin | 0° |
| False Easting | 600,000 |
| False Northing | 10,000,000 |
| Scale Factor | 1.0 |
| Linear Unit | Metre |
| Geodetic Datum | WGS84 |
Old Namibian Map System and Cadastral Datum
Older topographic maps in Namibia, as well as the official
cadastral system, are based on the Schwarzeck Datum.
The Schwarzeck Datum uses the Bessel 1841 spheroid and the German Legal Metre (GLm) instead of the International Metre (m): 1 GLm = 1.0000135965 m.
The projection used on older topographic maps and in the cadastral system is a south-oriented Transverse Mercator projection with two-degree panels.
Historic topographic maps are available online: Topographic Maps of Southern Africa .
Projection Parameters
| Projection | Transverse Mercator, south-oriented |
|---|---|
| Central Meridian | 11°, 13°, 15°, 17°, 19°, 21°, 23° or 25° E |
| Latitude of Origin | 22° S |
| False Easting | 0 |
| False Northing | 0 |
| Scale Factor | 1.0 |
| Linear Unit | German Legal Metre |
| Geodetic Datum | Schwarzeck |
The coordinate reference systems used for Namibia's two-degree map panels are documented in the EPSG Geodetic Parameter Dataset.
The EPSG codes below provide links to the corresponding system definitions on EPSG.io:
Schwarzeck Datum: EPSG:4293
Schwarzeck / Lo22/11: EPSG:29371
Schwarzeck / Lo22/13: EPSG:29373
Schwarzeck / Lo22/15: EPSG:29375
Schwarzeck / Lo22/17: EPSG:29377
Schwarzeck / Lo22/19: EPSG:29379
Schwarzeck / Lo22/21: EPSG:29381
Schwarzeck / Lo22/23: EPSG:29383
Schwarzeck / Lo22/25: EPSG:29385
Note: Some GIS and CAD applications do not support south-oriented projections. In such cases, coordinates may be sign-reversed and used with a north-oriented Transverse Mercator projection. The German Legal Metre may also be replaced by the International Metre using a scale factor of 0.9999864037.
The effect of the German Legal Metre is small over local distances (14 mm over 1,000 m). Surveyors generally account for this difference by incorporating it into a scale factor. Over larger distances, the effect becomes more significant, particularly farther from the latitude of origin at 22° S. It can reach approximately 7.5 m in the north and 10 m in the south of Namibia.
Older Local Cadastral Survey Systems
Before the official introduction of the projection described above in the 1950s and 1960s, longitude origins of 15° E or 18° E were also used. These are generally referred to on cadastral documents as preliminary systems, for example Lo.22/15 Prelim and Lo.22/18 Prelim.
Various other local cadastral survey systems were established before the official Schwarzeck system covered the whole country. Examples include the Base North (V) System in northern Namibia, the Schwarzrand System in south-western Namibia, the Kaiser-Wilhelm-Berg System around Windhoek, and the Uitdraai System east of Otjimbingwe. These systems can still be encountered on older farm diagrams and general plans.
Datum Conversion
Datum transformation parameters from the Schwarzeck datum to WGS84 have a countrywide accuracy of approximately 30 m.
Commonly used parameters consist of a translation (shift) only, with no rotation or scale factor.
The following parameters are available from:
- DMA (US Defense Mapping Agency) - EPSG:1226
From Schwarzeck to WGS84: DX: 616 DY: 97 DZ: -251
From WGS84 to Schwarzeck: DX: -616 DY: -97 DZ: 251 - Chief Directorate Surveys and Land Information; Mowbray; South Africa - EPSG:1271
From Schwarzeck to WGS84: DX: 615.64 DY: 102.08 DZ -255.81
From WGS84 to Schwarzeck: DX: -615.64 DY -102.08 DZ 255.81 - Dr Charles Merry (UCT - University of Cape Town)
From Schwarzeck to WGS84: DX: 616.8 DY: 103.3 DZ: -256.9
From WGS84 to Schwarzeck: DX: -616.8 DY: -103.3 DZ: 256.9
Use the free Schwarzeck Transformation App to transform between different coordinate systems in the WGS84 and the Schwarzeck datum:
Local transformation parameters vary by region, with an RMS of about 1.5 m, for example in the north-western region (see Projects – Transformation Parameters ), and about 0.3 m in the central area.
Namibian Vertical Datum
The vertical datum in Namibia is based on heights above Mean Sea Level (MSL). Most published heights of trigonometrical beacons were determined by trigonometrical levelling and are given to the nearest metre or to one decimal place.
More accurate heights are available in certain areas where precise levelling has been carried out. Benchmarks are located at approximately one-mile intervals along these levelling routes. The map shows the routes for which precise heights can be obtained from the Surveyor-General's Office in Windhoek.
Windhoek: Normal Null (NN) Datum
In Windhoek, a different levelling datum is used, known as the Normal Null (NN) datum. The conversion between Mean Sea Level (MSL) and Normal Null is:
MSL = NN − 3.475 m
NN = MSL + 3.475 m
Windhoek: Normal Null (NN) Datum
In Windhoek, a different levelling datum is used, known as the Normal Null (NN) datum. The conversion between Mean Sea Level (MSL) and Normal Null is:
MSL = NN − 3.475 m
NN = MSL + 3.475 m