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Vertical Control Surveys
- Early vertical control was obtained from heights obtained by using aircraft type altimeters and later Aneroid type barometers. The history of vertical control acquisition in Natmap is summarised in this 1988 paper by Manning and Menzies.
- The Natmap Johnson Ground Elevation Meter (JGEM), was one of only a handful ever manufactured. In Australia, the Royal Australian Survey Corps (RASvy) also used the JGEM for mapping. The Johnson Ground Elevation Meter article is via the link.
- To produce the contoured 1: 100,000 scale topographic maps from aerial photography, height or vertical control was required. National Mapping found that known ground based methods proved to be too slow or unsuitable for Australian conditions. An airborne solution was thus sought. The Laser Years : Recollecting Airborne Terrain Profiling for Photogrammetric Vertical Control in the Division of National Mapping, 1962-1982, by Paul Wise, provides the most detailed account of the Division of National Mapping's, airborne terrain profiling program. It was this program that generated profiles of the terrain from which the location and height of selected points were extracted, enabling Nat Map's vertical control requirements to be met.
- Joe Lines 1971 paper Application of Airborne Profiling to 1:100 000 Scale Mapping discusses the reason for the adoption of this technology by Natmap and the Airborne Profile Recorder, used by Natmap under contract, is described here.
- An early paper on the development of the Airborne Profile Recorder (APR) by the Photographic Survey Corporation (PSC) of Canada, titled The Airborne Profile Recorder by BI McCaffrey, Project Engineer, PSC Applied_Research, The Photographic Survey Corporation Ltd, Canada, National Mapping Bulletin by the National Mapping Council, Vol.1, No.3, April 1951, extracted from Photogrammetric Engineering, December 1950.
- Between 1971 and 1980 the Division of National Mapping's Laser Terrain Profiler, WREMAPS I, acquired over 250,000 kilometres of terrain profiles which provided vertical control for the photogrammetric plotting of 2.7 million square kilometres (the area of Australia is 7.7 million square kilometres) at a scale of 1:100 000 with a contour interval of 20 metres. Paul Wise's 1979 Technical Report 26 'Laser Terrain Profiling' summarises the complete program.
- The National 3rd Order Levelling Survey was undertaken from 1965-70. Almost in parallel mean sea level for Australia was established allowing the 1971 determination of the Australian Height Datum (AHD). The Australian National Levelling Network Survey, Australian Height Datum and Australian Vertical Working Surface describes the work involved in establishing the Australian Height Datum (AHD). The private sector played the major role in this program, in that private surveyors under contracts arranged by National Mapping and overseen by the States, carried out 60 per cent of the required levelling surveys. One such survey entailed around 500 kilometres of two-way levelling from Pedirka in South Australia across some 1,100 sand hills in the Simpson Desert to Birdsville in Queensland. The original paper has been updated to include the 2020 introduction of the Australian Vertical Working Surface (AVWS) and a method for most users to determine an AHD height from their GPS height.
- The National 3rd Order Levelling Survey and subsequent 1971 determination of the Australian Height Datum (AHD) are described in the following :
- Granger, Harry William (1972), The Australian height datum, Australian Surveyor, Vol. 24, Issue. 4, pp. 228-237;
- Roelse Adrian, Granger Harry W and Graham John W (1975), The Adjustment of the Australian Levelling Survey 1970-71, Technical Report 12, Department of National Development, Division of National Mapping 1975 - 2nd ed.
- Field Instructions for Nat Map 3rd order levelling surveys may be viewed for 1968 and 1969.
- Levelling connections to third order specifications, to selected Aerodist and Theodolite/Tellurometer traverse stations were undertaken in the Tanami region of the Northern Territory. These connections were to enable the heights of the selected stations to be related to AHD. Herein, some of the work during September/October 1972, is described and the permanent record of this work may be viewed.
- The map at the end of this 1965 report by Alan J Flavelle titled Helicopter Survey by Contract, NT & Qld. 1965, Part 1, BMR Record 1965/212 shows the indicative routes, across the Tanami Desert, of level traverses indexed DD and DE.