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GENERIC STEP-BY-STEP APPROACH STEP TWO

The steps to follow in geo-coding your service point addresses include the following:

 Obtain a complete list of your service points in electronic format, including:
o The physical addresses of the service points, for example, street number, street name, and
street type as follows: 22 Smith Road.
o The geographic places where the service points are located, for example, suburb, town,
village and city.
 Acquire the spatial information that will be used to do the geo-coding, for instance:
o National address directory or street address database which contains geographic coordinates.
o Geographic places of Statistics South Africa.
Use GIS or specialist geo-coding software to geo-code the database of service points, clearly indicating
the level to which they have been geo-coded, for example street, suburb, town, village or city level.

Use Google Earth to check the geographic position of the service points and adjust these positions if
necessary.

Figure 14: Illustration depicting the geo-coding process (Africascope 2009)

A very important aspect of spatial data is the coordinate reference system that is used. A Geographic
Coordinate System (GCS) uses a three-dimensional spherical surface to define locations on the earth. A
Projected Coordinate System is flat. It contains a GCS, but it converts that GCS into a flat surface.

The geographic coordinates of the service points of departments are generally provided in a GCS, for
example, latitude/longitude. However, geographic coordinates are not as accurate in distance calculations
as with projected co-ordinates, which are required for doing accessibility studies.
You should therefore transform your service point datasets from a geographic to a projected coordinate
system. A commonly used projection is the Transverse Mercator or Lo projection, giving you coordinates
in the South African Coordinate System.

ACTIVITY 4: QUALITY CONTROL THE DATA

Thanks to the development of modern technologies, data capture has become easier, but the risk of poor
data quality has increased.

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