History of National Mapping in South Africa

In 1904 the necessity of a national mapping programme was first discussed but never materialised due to funding difficulties. The (British) War Office (Royal Engineers) did map the Orange River Colony at the scale 1:125 000 and the north-west Cape at 1:250 000 but thereafter nothing much was done other than ad hoc mapping.

A national mapping programme was again considered after Dr WC van der Sterr was appointed first Director of the Trigonometrical Survey of the Union of South Africa in 1920.

In 1928 experiments commenced with terrestrial photogrammetry over the Cape Peninsula. This culminated in a 1:25 000 map with 25 foot contours. The terrestrial photogrammetric method was, however, deemed unsatisfactory. Further experimentation was performed employing different techniques and using different scales of mapping.

In 1936 a landmark decision was made to map the country at 1:50 000 (with some areas at 1:25 000) and that aerial photography would be used. Thus commenced the first 15 year plan. Mapping was carried out using plane table techniques combined with a variety of photographic interpretation techniques. Despite the published scale of 1:50 000, right up until the early 1960's, sheets were generally compiled at 1:18 000 (and 1:36 000) to enable engineers and other users to use copies of the large scale compilations, at the (then convenient) scale 500 yards to the inch.

Most domestic mapping operations ground to a halt during World War II. However, as so often happens, war stimulates technological innovation, and by the end of the war, superior aircraft and camera systems became available for mapping purposes.

In 1948 Trigsurvey ordered its first photogrammetric stereoplotters.

In 1952 a decision was made to make use of private sector contractors to fly aerial photography (and perform other mapping work). Prior to the war Trigsurvey had had its own aircraft and flew its own photography. Immediately after the war, photography was flown by the air force. The private sector were able to supply a product better suited for mapping purposes.

By the early 1960's, only 20% of the country had been mapped at 1:50 000. Then in March 1961, W van Breda Smith became Director of Trigsurvey and in 1962 put a new 15 year plan into action. This coincided with many developments in the air survey industry such as super-wide angle photography and electronic computers. An important decision was also made to compile at 1:50 000 and to employ private sector land surveyors to perform field work.

This time the 15 year plan was successful and on 8 May 1973 the last 1:50 000 sheet was compiled (and published in March 1976).

South Africa adopted the metric system in 1970. Consequently, when the 1:50 000 series was completed in 1976, about 60% of the sheets used the foot as unit of measure and the remainder metres. All contours had to be recompiled. The last metric sheet was published in 1992.

Experimentation commenced in 1977 with ultra-small scale super-wide angle photography at scale 1:150 000 flown to orthophoto specification, i.e 90% overlap flown along prescribed flight lines. Eventually the whole country was covered at this scale. From this, 1:50 000 orthophotos were produced for detail revision. Contouring and detail compilation, in flatter areas, directly from the small scale photography was also undertaken. This photography was relatively expensive but the savings at aerial triangulation and compilation were enormous - three overlapping models covered an entire 1:50 000 sheet. 1:50 000 orthophoto maps were never produced, except for some sheets in the Kalahari which were enhanced by the addition of the orthophoto background to the conventional line map. A nation wide 200/400 metre DEM was a byproduct of this programme.

This mapping is generally confined to urban and peri-urban areas of dense detail and to rural areas with growth potential; approximately 25% of the country is covered with this mapping. A 50 metre DEM has been generated as a byproduct of the 1:10 000 orthophoto mapping programme.