MAPPING A CONTINENT
by Colonel Lawrence FitzGerald, OBE, Director of Military Survey
(Walkabout, Australian Geographical Magazine, Journal of the Australian Geographical Society, Vol.14, No.10, 1 August 1948, pp. 9-15 accessed at : https://nla.gov.au/nla.obj-739085301)
Those who have travelled in Great Britain will be familiar with the mass of detail in the Ordnance Survey Maps so readily available in that country. These range from the large-scale plans at 25 inches to the mile used by the estate owner or agent as a basis of title, through the medium-scale maps at one to 25 000 scale and one mile to one inch showing all cultural features and contours so ideal for development of planning, to the smaller scales of two, four and sixteen miles to one inch, more useful to the tourist or road-user. They surely provide the answer to all enquirers regarding geographical location and topographical facts. Such maps are indeed a national asset quoted and envied by many European States, and an example to Survey organizations in Australia of what can be achieved.
It is of course futile and unreasonable to expect the same achievement to be reached in this country, because of the adverse factors of low manpower and vast areas which require a hundredfold comparative effort. On the other hand, however, because of our large extent of relatively waste lands, it is quite sound to assume that small-scale maps at say four miles to one inch will suffice for many generations to come over the greater part of the continent, with the larger scale mapping of one to 25 000 or one mile to one inch restricted to the developed zones or to those areas which are important on account of closer settlement, water conservation, mining, forestry, rail and road development.
Maps have already been published covering the shaded areas.
At this stage it is necessary to differentiate between the plan and the maps. The farmer or pastoralist at least will be familiar with the parish, hundred, county, or pastoral plan as produced by the State Departments of Lands and Surveys. These indicate primarily property boundaries and roads according to title or lease. The main drainage features, and sometimes the mountain ranges, are indicated in broad terms, but cultural features and relief are not depicted. Such plans serve the purpose for which they are intended but are deficient in topographical data, and they are often misleading in that access roads and boundaries in title are not in fact physical features at all, nor are they apparent or existent on the ground. The map, on the other hand, depicts all cultural features, including dwellings, roads, railways, timber, water, bridges, telephones, and such developments as actually exist and are within the limitations of map scale. In addition, the large and medium scale maps show relief by contours, and the smaller scale by hachures or layers. The plan is normally a one-colour production, while the map is multi-colour, permitting easy interpretation of the mass of detail shown. It is with the topographical map that this article is concerned.
Just as the Army took the initiative in Great Britain with the production of topographical maps of the Highlands of Scotland following the rebellion of 1745, from which the great Ordnance Survey developed, so did the Australian Army take the initiative in this country in 1908-9. Six members of the Ordnance Survey were obtained on loan to commence the Military Survey of Australia. Shortly after, the Australian Army Survey Corps was formed, and was supplemented by recruiting from Australian personnel. Its sphere of operations covered training, tactical and strategic areas mainly around the capital cities of the States, and before long the one mile to one inch maps became familiar and available to the general public and in great demand by the engineer, the planner, and those concerned with developmental projects. From this small beginning the Survey Corps developed slowly until 1939, when the war impetus provided a strength of about a hundred, ultimately reaching a peak in 1944 of 1 800 enlisted personnel. This resulted in a rapid extension of map coverage in all States, particularly in Queensland and the Northern Territory. In 1942, however, New Guinea became the focal point of concentrated effort, with subsequent decline on the mainland. The operational mapping of the Survey Corps covered fields afar, including surveys of the border zones of Palestine, Syria, Transjordan and Turkey, then back to the Pacific theatre, where extensive mapping was carried out in New Guinea, New Britain, Bougainville and the Philippines, culminating in the last offensive in Borneo. Most of this mapping was at tactical scales of one mile to one inch, or larger. An interesting development was the production of a four-mile-to-one-inch series covering about one-third of the mainland. This series was a re-compilation of existing data into a standard and convenient form. It was not based on new survey or field investigation. It is admittedly very much below standard, and will be referred to subsequently.
Consequent on general demobilization, the Survey Corps strength diminished considerably, but nevertheless its present figure is much greater than any reached in pre-war days. Plans for the post-war regular Army provide for the maintenance and recruiting of an even greater force, and a long-range programme of mapping is already in hand.
The production of topographical maps of an extensive continent involves much planning and many stages. Those familiar with military maps will recall the over-printed grid, which is not solely a system of reference but also indicates a co-ordinate value based on a very accurate survey. One will realize that continuity of a grid and of detail is necessary over all sheets of a series. This involves a triangulation survey, visual evidence of which appears as beacons on prominent hills throughout the countryside. Such beacons may consist of steel or bush-timber quadrupods or cairns of stones supporting a central pole, on tops of which are sheet-iron discs which from a distance appear to the observer as a black sphere on the sky-line. These trigonometrical beacons are the surveyors’ observation stations. Angles to and from them are taken with a theodolite, and provide the means of computing the bearing or azimuth and the distance to other such marks. The beacons, in addition, are permanently marked with a buried concrete block so that the exact point can be re-established should the beacon be destroyed. The layman may be surprised to learn that very little actual measurement of distance is done. The chain of triangulation is tied to what is known as a base line. This line is normally six to ten miles in length, and is measured to an accuracy within one part in a million, which is of the order of half-an-inch in eight miles. For this accuracy measuring bands of Invar are necessary in order to reduce the effect of temperature errors. The Army Survey Corps has developed a technique of temperature measurement by using what is known as the electrical resistance method, which is far more accurate than any field thermometer. Astronomical observations at the base line and elsewhere provide absolute values of Latitude, Longitude and Azimuth on which the triangulation network is adjusted. An interesting development in this respect is the time signal broadcast from Belconnen and originated at the Commonwealth Observatory, Canberra. This was commenced during the war as a special aid to Army surveyors in their determination of longitude in previously un-surveyed areas of the mainland and New Guinea. The signal extends over a five-minute period at selected times of the evening, and is of the rhythmic type, beating 61 times to the minute and thus giving a vernier comparison with the field chronometers to an accuracy of one- or two-hundredths of a second.
Survey Corps quadrupod beacon on Mount Norman (4 066 feet), Queensland.
Triangulation station on Mount Kosciusko showing beacon, theodolite, heliograph and signalling lamp.
Measuring a baseline at Benambra, Victoria.
The triangulation survey is the framework for subsequent detail mapping. The old method involved the extensive use of the plane table, which is now becoming a lost art and is superseded by the practice of mapping from air photographs. The Survey Corps used air photos, in 1930, being foremost in this field in Australia, and this method is now used for all military mapping. An examination of the air photos, illustrated shows what a mass of detail is evident. The photo, however, is not a true map in itself as it has inherent distortions due to camera tilt and variations of ground relief which the surveyor and draughtsman have to eliminate.
The compilation of the detail map therefore involves the elimination of photo scale errors, interpretation, annotation and the subsequent conversion to the conventional map. The field surveyor also establishes sufficient heights for contouring, which is then done with the aid of stereoscopic equipment. This equipment ranges from simple hand stereoscopes to the more elaborate and precise plotting machines, each of which has its special application. The Army Survey Corps favours what is known as Multiplex. This device consists of a battery of projectors which can be set in the same relationship of spacing, height and tilt as the original air cameras at instants of exposure. The images are projected in alternate red and blue colours which, when viewed through spectacles of complementary colours, give a true three-dimensional model of the terrain. Plotting and measuring devices then convert this image into the conventional map and eliminate a considerable portion of the field work otherwise required. The next stage is the fair drawing, which is the finished article as far as the draughtsman is concerned. The last stage is the lithographic reproduction of the map in its final form. This involves photography of the fair drawing, the preparation of the lithographic zinc plate for each colour, and then the printing of the map for issue. The figure of twenty million maps printed by the Survey Corps gives some idea of the requirement in wartime at least,
Mosquito aircraft of R.A.A.F. Photographic Squadron (Photo: R.A.A.F.).
First phase examination of air photos to ensure complete coverage.
Projecting photo detail on to the map compilation using the “oblique sketch master”.
The “Stereocomparator” used for precision parallax measurements on air photos.
Plotting detail from oblique photos on to the compilation sheet by means of the “angulator”.
Plotting contours on air photos by means of the topographical stereoscope and parallax bar.
Photogrammetric air cameras ; (Left) Williamson Ordnance Survey Camera (OSC), 1946; (Right) Fairchild K17.
Closely associated with the work of the Australian Survey Corps is that of the R.A.A.F. Photographic Squadron, with its Headquarters at Canberra. This unit, like its Army partner, has long since reached maturity and is also settling into its post-war stride. It is equipped with high-performance Mosquito aircraft, and with Lincolns for special occasions. Its capacity for survey photography can be visualized from its covering, in the first five months of 1948, of 100 000 square miles over many remote parts of the mainland.
Air photography for survey is very exacting, involving flying at heights of 15 000 or 25 000 feet above sea level, close attention to navigation, horizontal flight and accurate timing of the camera to obtain the specified overlaps of exposures. Specifications for photography are defined by the Army Survey Corps, which supplies liaison personnel with the R.A.A.F. squadron and detachments in the field. These liaison surveyors assist R.A.A.F. with the marking up of the proposed flight lines on existing maps or on key strips flown for the purpose. It is then R.A.A.F.’s responsibility to produce photography to specifications. On completion of a sortie, the films are developed and one set of prints is obtained without delay. These prints are examined for overlaps, gaps and definition, so that any sub-standard work can be re-flown before the detachment leaves the area. On the satisfactory completion of a task, the negatives are forwarded to the Base Negative Library, where subsequent requirements for prints are processed.
It is easy to appreciate that this team of Army surveyors, draughtsmen, and printers, together with R.A.A.F.’s pilots, navigators and photographers, is building up a national asset of topographical and geographical information available not exclusively to the Armed Forces but also to every organization concerned with planning and development, and within reason to the general public. It is not generally realized that the Army Photo. Library has filed air photos, covering about a million square miles of the mainland and New Guinea, and this is just the start of a long-range programme which is intended to cover the whole of our territory, excluding perhaps the most desolate and waste areas, and concurrently with photography will proceed the mapping at one or four miles to one inch. The military application is obvious, and so also is its application to the needs of the road and water supply engineer, the soil and forestry experts, the town-planners, and the farmer and pastoralist. What an asset to the last would be a photographic mosaic showing every detail of drainage, the river flats, the hill country, water holes, fences and timber.
The long-range Army and R.A.A.F. mapping programme is adjusted to give some priority to urgent investigations for developmental projects. This has already resulted in R.A.A.F.’s photography covering areas including the Blair Athol coalfields, the Burdekin River and Nogoa-Comet River areas, the South-west Channel country in Queensland, the Barkly Tablelands in the Northern Territory, part of the Kimberleys, the Fitzroy River and Hammersley Ranges in West Australia, extensive areas in South Australia, and the upper reaches of the Snowy River.
An interesting diversion of the Army Survey Corps involved the survey and mapping of the Kosciusko area in connection with investigations for the proposed diversion of the Snowy River for hydro-electric and irrigation schemes. Existing maps of this area were hopelessly inadequate and erroneous. Incidentally the publication of the Kosciusko map this year should be welcomed also by tourists and skiers.
Another example of diversion of activities was the preparation of the maps required for the 1947 census.
A technical development worthy of mention is the application of radar to surveying. Just as World War One gave an impetus to the use of air photos, so did World War Two produce a method equally revolutionary in the field of surveying, and that is the development of radar. It is now common knowledge that radar was used extensively in air navigation and bombing, but the greater accuracy required before it could be applied to surveying necessitated some special investigation and equipment. The impetus for this development came from the South-east Asia Command, as that theatre was so inadequately mapped for military operations that the only practical solution was some method of mapping enemy-occupied territory by remote control. The responsibility for producing the answer was given to the Directorate of Military Survey at the War Office in England, and in the comparatively short time that has since elapsed a practical and satisfactory technique has been developed.
Radar applied to surveying employs the measurement of distance which is related to the time interval of radio pulses and the rate of propagation of the radio waves. The stage has now been reached at which the course of an aircraft can be followed with an accuracy of within about twenty yards. In the case of a survey photographic aircraft this means that the location of the camera at the instant of exposure can be determined. In conjunction with photogrammetric equipment, the resultant photo, can be analysed for tilt, and all points of detail visible on the photo, can then be plotted on the conventional map in true position; this can be done by remote control involving no survey party nearer than say 150 miles.
Another application of radar is the measurement of lines up to 500 miles long with an accuracy comparable to high-order survey triangulation. By this means it would be practicable to determine the position of a survey mark, say in Broken Hill, in correct relation to surveyed positions in Melbourne and Sydney. This application would largely overcome the existing deficiency in co-ordinated surveys which unfortunately is the state in Australia to-day.
The Army Survey Corps and the R.A.A.F. Photographic Squadron are jointly interested in this development, and a team of two officers of each organization has recently returned from England after investigating developments and technique in that country. In addition the Radio Physics Branch of C.S.I.R. is active in research concerned with equipment and factors perhaps peculiar to our territory.
The field for radar surveying lies in our empty centre, the remote north-west and north, and the jungle-clad ranges of our mandated territories. It has not yet solved the problem of determining the third dimension, that is, elevation or contours, but with the help of Multiplex equipment the complete solution should not be far distant.
The national aspect of military mapping and air photography is fully appreciated, and advisory bodies have been set up to ensure a co-ordination of activities between service and civil agencies. The Commonwealth Survey Committee consists of the Commonwealth Surveyor General and representatives of the Departments of the Navy, Army and Air, Civil Aviation, Post-War Re-construction, C.S.I.R., and the Bureau of Mineral Resources.
A similar committee which includes State representation is the National Mapping Council, consisting of the Commonwealth Surveyor General, the Army member of the Commonwealth Survey Committee, and each of the six State Surveyors General.
The broad function of these bodies is to co-ordinate the activities of Government mapping agencies, to prepare standards for technical procedure, and to pursue an active policy for national mapping.
It is gratifying to realize that a very progressive attempt is now being made to map our country and to create an asset that must contribute handsomely to the assessment of our national resources and the defence of our country.
New Guinea’s rugged terrain. “It is not generally realized that Army Photographic Library has filed photographs covering about a million square miles of the mainland and New Guinea” (Photo: R.A.A.F.).
Earth Patterns : (Left) Sandstone and river country in the vicinity of Borroloola, Northern Territory; (Right) Mangrove swamps in Arnhem Land, Northern Territory (Photos: R.A.A.F.).
Oblique air photograph of country in the vicinity of the Rawlinson Range, central Australia. (Photo: R.A.A.F.).