Maps and Geospatial Information

This includes the popular 1:10 000 orthophoto and 1:50 000 topographic, numerous other smaller scale, provincial and national maps. Orthorectified imagery, elevation data (including DEMS), vector topographic data as well as raster maps are available digitally.

 

SA Mapsheet Referencing

General

  1. Each map of the National Map Series is identified by its unique number (e.g. 2830CB) and scale, or by name (e.g. 331 8 Cape Town, 1: 250 000).
  2. All maps produced by the National Geo-spatial Information are referenced to the Hartebeesthoek 94 Datum (WGS84 ellipsoid).

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Topographic Data (Vector)

What is GIS Vector Data?
 
This is the representation of reality in the form of features (points, lines and areas) whose locations are stored as X, Y co-ordinates (its Spatial Attributes). In some instances these features would also contain the Z (height) co-ordinate, such as the in a contour feature. Non-Spatial Information or Attributes are also stored within the feature, this would give you descriptive information about this feature.

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Elevation Data

DEM (Digital Elevation Model) data describes the surface of the earth through a regular rectangular grid which can be visualised as a wire grid framework draped over the surface of the earth. Each grid intersection is defined by two components, i.e. a coordinate reference grid location(y, x) and associated height (H). The coordinate and associated height components are referenced to separate earth reference systems, i.e. a two dimensional (y, x) and one dimension (H) reference system. Collectively, the reference system can be described as a Compound Coordinate Reference System (CCRS) [ISO 2002]. The y and x coordinates are referenced to the Datum's and Coordinate Systems while the height component is reference to mean sea level.

Read more: Elevation Data