1:50 000 NATIONAL MAP SERIES
The Dutch East India company established a base at the Cape of Good Hope in 1652.The first settlers were allocated land to farm and provide fresh vegetables, fruit, meat and water to the ships that were sailing via the Cape on route to the east. Land was allocated to settlers initially without being surveyed and eventually as more settlers arrived, the disposal of land was based on the Land Registry system which had long been in use in the Netherlands. Although every title deed was accompanied by a diagram showing its boundaries and area, the grant of land had not been fixed by survey. Many of these areas were measured by pacing a roughly circular (approximately 4 kilometre radius) shape around a central position. This gave rise to many abuses and disputes over farm beacons which often led to litigation and dissatisfaction. It was not until 1813 that efforts were made to improve the system.
In 1904 the necessity of a National Mapping Program that would benefit civil society as well as the military was discussed. The British War Office undertook mapping of the Orange River Colony at 1:125 000 scale and the North West Cape at 1:250 000 scale, thereafter nothing other than ad hoc mapping.
In 1928 experiments commenced with terrestrial photogrammetry which eventually led to a landmark decision in 1936 to map the country at 1:50 000 scale. A fifteen year plan was commenced using aerial photography, plane table methods and a variety of photographic interpretation techniques. Despite the published scale of 1:50 000 right up to the early 1960’s map sheets were compiled at 1:18 000 and 1:36 000 and copies of these large scale compilations were used by engineers and others at the then convenient scale of 500 yards to the inch.
Most domestic mapping operations ceased during World War II. The war led to many technical innovations and major advances in aircraft and camera technology and by the end of the war this became available for mapping purposes.
Prior to the war Trigsurvey had its own aircraft and flew its own photography. The Airforce flew aerial photography in the post war period and later the private sector was able to supply a product better suited for mapping purposes.
In 1948 the first photogrammetric stereo-plotters were commissioned and the capture of topographical data from aerial photography commenced. By the early 1960’s only 20% of the country had been mapped at 1:50 000. In 1962 a new 15 year plan was introduced which coincided with new developments in the air survey industry such as super wide angle photography and electronic computers. A decision was made to compile at 1:50 000 and employ private sector land surveyors to perform field work. The complete coverage of South Africa mapped at a scale of 1:50 000 was achieved in 1976.
South Africa adopted the metric system in 1970 and all maps compiled prior to 1970 had to be metricated. This meant that for about 60% of the country the contours had to be recompiled.
In 1992 the last metric sheet of the National 1:50 000 map series was published.
The manual cartographic process previously known as fairdrawing has made way for a new Computer Assisted Map Production System which was introduced in 1997. The modern computerized map production system has had many benefits including increased production and value added products such as digital map images.
The 1:50 000 National Map Series comprises 1913 map sheets and is the largest map scale providing complete coverage of South Africa, an area of 1 221 000 square kilometers. Although there is full mapping coverage of South Africa, approximately 20% of the country still has to be produced as a digital product.
1:10 000 ORTHOPHOTO MAPS
Map compilation at 1:18 000 was discontinued in the early 1960’s and with the eminent completion of the 1:50 000 series a new large scale series was contemplated. There was and still is a demand for large scale mapping especially in the field of civil engineering. In 1968 the 1:10 000 Orthophoto Map Series commenced with full scale production, initially contracted out to the private sector and in 1971 the Chief Directorate assumed this responsibility. This large scale mapping is generally confined to urban and peri-urban areas of dense detail and to areas with growth potential. The manual cartographic process was replaced by a Computerised Map Production System in 2000. The introduction of computer technology not only increased production, it also produced value added products such as digital images and a 25 metre Digital Elevation Model. Approximately 30% of South Africa is covered by 1:10 000 Orthophoto maps.
1:250 000 TOPO-CADASTRAL MAPS
The early 1:250 000 scale maps were produced for military purposes during World War II. Later edition 1:250 000 maps were derived from the component 1:50 000 maps which had been compiled as part of the 15 year plan. Each 1:250 000 map has 32 1:50 000 component maps. Following on the success of the Computer Assisted Map Production System introduced for the 1;50 000 series, this national map series too replaced the manual production methods with new computer technology. Value added products emanating from the new process include digital images and a seamless data base covering South Africa at 1:250 000 scale. There are 70 1:250 000 maps in this series.
1:500 000 TOPO-ADMINISTRATIVE MAPS
Between 1934 and 1937 maps at 1:500 000 scale covering South Africa were produced by the then Department of Irrigation . Known as the “Lewis Maps” they were the first topographical map series to provide full coverage of South Africa. On completion of the 1:50 000 series the 1:500 000 series was completely revised. Revision of the series commenced in 1974 and was completed in 1984. Magisterial District and Administrative boundaries based on information supplied by the Municipal Demarcation Board were added to the topographical information as an overlay. Computer Assisted Map Production has also been introduced for this series and the 1:500 000 series maps are now derived from the larger scale 1:250 000 series. Value added products from this series include digital images and the background topographical base maps which are used to produce Aeronautical Charts. The Aeronautical information is printed as an overlay on the 1:500 000 Topographical base maps. There are 23 1:500 000 maps in this series.