Feature Article - Tasmanian mapping in the 20th century
Contributed by Department of Primary Industries, Water and Environment
At the beginning of the 20th century, no accurate topographical maps of Tasmania existed, indeed, very little of Australia was accurately mapped. World War I provoked limited activity in this field and a contoured map of the area between Hobart and Kingston was prepared for defence purposes only and was not made available to the public.
Prior to this, the only maps or charts available were small-scale maps of the whole State or the cadastral or county charts at a scale of 40 chains to 1 inch. Such charts, while compiled from actual surveys, were not controlled by the State triangulation, which was carried out by James Sprent in the 19th century. As a result, compilation errors tended to accumulate over distance. Also, very little cognisance was taken of topographical detail and no contours were shown at all.
At some time during the early part of the 1920s, the Mines Department produced two large-scale multi-coloured maps with contours in the Montagu River area. These were prepared using theodolite and dumpy level and consequently could be considered as the first accurate topographic maps produced in Tasmania, but their existence was not widely known.
During the 1920s and 1930s, the Forestry Department carried out topographical surveys of its plantation areas, usually with prismatic compass and Abney level. Towards the latter part of this period, it commenced compilation of its divisional maps at a scale of 2 miles to 1 inch using any maps or charts available, together with some field reconnaissance. These maps did not, in general, show contours or form lines but were the best general topographical maps available up to that time.
The outbreak of World War II in 1939 made Australia realise that it did not have suitable topographic maps available should an invasion of its shores occur. As a result, emergency mapping organisations were set up in each State under a Deputy Assistant Director of Surveys. In Tasmania, this operated under the umbrella of the Lands and Surveys Department as it did elsewhere. Sprent’s triangulation was recalculated and used as control for the plane table surveying of four 1 mile to 1 inch maps. Three of these sheets, Brighton, Hobart and Sorell, were produced without contours but the Buckland sheet was published with 50-foot contours using an alidade in conjunction with the plane table surveys.
Prior to these maps, however, several sheets covering the State were compiled using county charts, Forestry maps etc., supplemented by detailed field checks of road classifications for military purposes. These maps were published at a scale of
4 miles to 1 inch. Both series were published in four colours but were never released to the general public because they were for defence purposes.
Even before the cessation of hostilities, steps were being taken to implement a national mapping program and in the post-war years the Division of National Mapping in Canberra was established as well as mapping organisations in the States. A National Mapping Council was formed, bringing together all States and including the Army, Navy and the Commonwealth Survey Department. Standard Map Specifications were promulgated.
The Division of National Mapping and the Royal Australian Survey Corps then commenced the triangulation and mapping of the whole of Australia at a scale of 1:250,000. This was to be followed by a series at a scale of 1:100,000.
Tasmania commenced its mapping by producing a trial series at a scale of 1:15,840 in the Longford-Cressy area. With increasing need by the Hydro-Electric Commission for contoured maps of the State’s river systems, mapping was commenced of unsettled areas at a scale of 1:63,360. This was quickly altered to a scale of 1:31,680. This mapping was made possible by the use of aerial photography and imported stereoplotters. The Lands and Surveys Department commenced an on-going program of aerial photography in 1946 using contractors from interstate. Subsequently, it acquired its own aerial cameras and utilised local aircraft.
When the Commonwealth adopted the 1:100,000 scale, Tasmania entered into an agreement both to compile and print all the maps in this series covering Tasmania. By doing so it was able to produce a parallel series for its own use. The State series was produced in a slightly modified form and was marketed in a convenient folded format.
Thematic mapping was carried out also by some other Government instrumentalities, notably the Mines Department, Hydro- Electric Commission and the Town and Country Planning Commission.
As in so many other fields, the latter half of this century has seen dramatic changes in the methods used for the production of mapping data. The traditional theodolite or compass and chain together with dumpy level or aneroid barometer were, after World War II, largely superseded by the tellurometer and aerial photography in conjunction with photogrammetric plotting machines.Within 25 years, however, the computer age began to make an impact with digital photogrammetry, satellite imagery, etc.
THE DIGITAL MAPPING ERA
Mapping in the last 10 years of the millennium has made the most rapid advances in its history to date. Prior to the 1990s, map production involved intricate and laborious manual processes that tended to make production of maps an expensive and time consuming task. Base topographical maps could take many months to produce and required the use of expensive ‘repromat’ (reproduction material) and photographic processing.
Because of the rapid advances in computer technology in terms of both speed and storage capacity, it is now possible to produce maps entirely on computer without the need to use manual or photographic processes. Maps produced in this way can, in many ways, be compiled using automated procedures with limited input and direction from the computer operator. Producing maps by this method makes the task much less time consuming and expensive than the previous cartographic processes used. Maps are also more accurate and much easier to update.
The digital mapping era, because of the accessibility of topographic information and computer technology, has widened the use of topographic data into many areas that previously had little exposure to mapping. The retail industry, for example, uses topographic data for market research and planning, while the police use topographic information for planning and crime analysis. The uses for digital topographic data are wide and varied and there is no doubt that in the future it is likely to become more so.