Assistant Director, Division of National Mapping
Reprinted from the National Development Quarterly, September and December,
Accurate maps have long been recognised as a basic requirement in the detection,
assessment and development of natural resources. A mineral prospector pegging a claim -
engineers designing and developing mines, roads, railways, ports and irrigation schemes -
surveyors setting out a new town. They all use maps.
Simply put, the map maker is called on to provide accurate "pictures - of particular areas
- or an entire country. He must show natural and man-made features in their correct
geographic positions and put in contours showing the true height of the land above sea
level. His "pictures" are topographic maps. The modern-age demand on him is for greater
and greater precision coupled with fast production.
The map maker has, therefore, sought scientific and technological help to replace tedious,
arduous and, at times, dangerous methods of survey and observation previously carried
out entirely by ground teams.
Permanent steel survey beacon at a station in a remote part of central Australia. The
helicopter is about to pick up a survey party and items of equipment flown in earlier.
Prior to the advent of aerial photography the earliest maps had been produced with the
aid of magnetic compass and tape, and in outback Australia sometimes by compass and
the measured tread of camels to determine distance travelled. Further instrumentation
was introduced and then came aerial photography.
Aerial photography was introduced to Australia in the early 1930's but was not used to
any great extent until World War II experience demonstrated its innumerable uses.
In the immediate post-war years, Australia moved to set up a national mapping
organisation - now the Division of National Mapping of the Department of National
Development,(1) and it was decided then to base all future topographic mapping on the
wealth of information which could be gathered relatively quickly from aerial photography.
A systematic programme was planned to cover the continent by overlapping photography,
each 9 in x 9 in photograph showing an area of approximately 50 square miles. (Later
equipment increased the coverage to about 140 square miles for each photograph.)
A pre-requisite to the use of photographs was the establishment of thousands of control
points which would permit map makers to fix the exact position of each photograph on the
face of the continent, and ensure that maps produced at a later stage would fit together
accurately to form a complete picture of the continent.
A primary set of points was established across Australia under a programme known
among surveyors and scientists as a geodetic survey. Such surveys had been carried out
in earlier years by State authorities and Army Survey, covering only relatively small areas.
The requirements of the national mapping programme, however, required a national
geodetic survey and this resulted not only in the complete coverage of the continent by
1966 but far greater accuracy than had been previously achieved. Further survey work is
now being undertaken to fill in open spaces between sections of the primary geodetic
survey and provide marks to fix the positions of aerial photographs.
Probably the greatest advance in modern surveying came in the mid1950's when
electronic instruments were developed to measure distances on the ground. This gave rise
to a new term, EDM - electronic distance measuring. This became the modern surveyor's
tape, and unlike any previous tape in that distances from a few metres to more than 50
miles could be measured at once to a few centimetres in accuracy.
Left: Perspective drawing shows how "Aerodist"
equipment in an aircraft is used to measure the
distance between two survey points.
Above: White concrete survey mark set by National
Mapping surveyors in western New South Wales.
The steel guide posts assist ground parties to locate the marker.
EDM quickly extended from ground equipment to airborne methods and is now installed in
satellites to take measurements across oceans. (Modern mapping makes extensive use of
the metric system of measurements so that the complications of feet and inches, chains
and links - odd mixtures of dozens and tens - are on the decline.)
EDM is used quite extensively in Australia to measure distances on the ground to assist in
establishing the geographical co-ordinates of survey stations which in turn are used to
position aerial photography. Geographical co-ordinates are simply latitude and longitude.
Ground measurements are restricted to "line of sight" conditions. As much of this country
is relatively flat, traversing large sections of open spaces necessitates more
measurements than would be required if the terminals of lines were more elevated and
lines correspondingly longer. These conditions are artificially produced by use of aircraft.
An airborne system used more in Australia than anywhere else in the world, and called
"Aerodist", measures long lines in two parts, that is to one ground station from an aircraft
while simultaneously measuring from the aircraft to a second station.
Left: "Aerodist" equipment installed by the
Division of National Mapping in a chartered
Grand Commander aircraft.
From a series of three simultaneous
measurements which show when the
aircraft is directly between two ground
stations, the actual ground distance
between them can be calculated. Lines up
to 200 miles long have been calculated in
this way to an accuracy of one or two
metres. This system permits a geometric
pattern to be built up over the open
spaces, and mathematically adjusted to
the basic geodetic survey with the aid of
electronic computers.
Helicopters save time for the surveyors
by placing ground station men and
equipment exactly in desired locations
when ground transport would be
In desert operations, the planning of this
work requires more than usual care as
ground station parties are heavily
dependent on the continued service of a
In addition to the acquisition of geographical co-ordinates, the third ingredient required
from field surveys is a number of spot heights accurately related to sea level. These
heights provide the starting points and the necessary checks for contouring from aerial
Once again, EDM is the technique to speed up the work and enable operations to proceed
virtually irrespective of terrain.
The Division of National Mapping uses airborne profile recording (APR) techniques very
largely for this work.
The present equipment, obtained on contract, employs the radar principle to measure the
distance (height) between the aircraft, which flies at a constant elevation, and the terrain
The heights are recorded on moving charts as continuous longitudinal sections, and
aircraft position is obtained by continuous vertical photographs of the terrain. From check
measurements of the aircraft over surfaces of known elevation, and other corrections,
heights can be deduced for selected points on the ground.
A further development of this technique is being undertaken at the request of the Division
by the Weapons Research Establishment of the Commonwealth Department of Supply.
Composite illustration shows a profile measured by a laser terrain recorder from an aircraft.
This employs the pencil beam of a laser light source, which, unlike a radar-type
transmission, can be contained to a cylinder of about 2 ft diameter at ground level from
an operating altitude of 7,000 ft. The modulated laser transmission is another form of
EDM, and because of its great pointing accuracy and sensitivity to change of distance,
provides a new and more accurate approach to establishing ground elevations from the
The Australian laser terrain profiling equipment has already been successfully flight tested
as a prototype.
In its completed form, it will be the first laser profiling equipment in the world constructed
specifically for surveying purposes. It will employ many sophisticated ancillary techniques,
and safe operation is a feature of its design. The low power level of the transmission will
not be a hazard to persons or property.
The Division employs an unusual vehicle to supplement the ground heighting programme.
This is the Johnson Ground Elevation Meter which looks rather like a station sedan at first
glance. Closer inspection reveals that it has five road wheels, four-wheel drive, four-wheel
steering (so that the rear wheels track exactly with the front wheels), air-conditioning,
automatic tyre pressure control and a large array of electronic equipment.
Left: National Mapping vehicle
equipped with a Johnson
Ground Elevation Meter.
The two quantities required
to calculate the difference in
height as the vehicle travels
up and down gradients (that
is the distance run and the
angles of the gradients) are
determined respectively by
the fifth wheel, and an
electro-magnetic pendulum
situated on a bar joining the
front and rear axles of the
vehicle, which is the plane of
reference. As this bar changes attitude, the deflection angles from a horizontal plane are
continuously computed from signals received from the pendulum.
The calculations of difference in height during travel are made electronically and recorded
in numerical form on a paper tape.
This is yet another form of EDM and produces results with an error less than 10 feet in 50
miles at 15 miles an hour on reasonably good road surfaces. This equipment is not
suitable for cross country travel.
The methods and equipment discussed in this article have been adopted to speed up and
improve the gathering of knowledge and measurements required by photogrammetrists
who convert the aerial photographs into manuscript maps which are then finally drawn by
cartographers as maps suitable for ultimate reproduction by lithographic printing
processes. This kind of map, a line map, is likely to be produced and used widely for many
years yet, but for some purposes it could be replaced by a form of map produced very
quickly by re-processing aerial photographs into "ortho-photos" produced by equipment
which is the closest thing yet to a "map making machine".
Photographs for the national mapping programme are taken from aircraft flying high east
to west and covering strips of 100 miles. The photographs in each strip overlap each other
by at least 60 per cent and each strip is designed to overlap its neighbour on each side by
25 per cent.
This pattern of flying provides near vertical photographic material for three-dimensional
(stereoscopic) viewing of the terrain. The cameras used possess precise qualities of lens
and mechanism and they are calibrated by the National Standards Laboratory of the
CSIRO in Sydney so that their geometrical properties are known accurately to a few
microns - thousandths of a millimetre.
To match these qualities, dimensionally stable photographic film is used and processed
under strict production conditions. Accuracy is vital because there is an image of about
140 square miles of country on each 9 in x 9 in frame of a roll film.
The subsequent processes in map preparation are based on positive transparencies
reproduced from the original negatives - again on dimensionally stable film.
These are made in equipment which not only produces an even-toned image by electronic
scanning, but at the same time removes the distortion in the original image attributed to
curvature of the earth.
After ground control points have been fixed in predetermined positions on a small
percentage of the photographs, the control data are used in graphical or mathematical
processes to derive further control points on each individual photograph.
These processes, which give substantial economies in the density of ground control
required, rely on extremely accurate measurements taken from aerial photographs and
are an important segment of the branch of surveying known as photogrammetry. This is
the science of taking accurate measurements from photographs.
An overlapping pair of transparencies is then introduced into a stereoscopic plotter in
which can be seen a stereoscopic model. Map makers know the apparatus as a "stereo-
plotter" and the model as a "stereo-model".
Left: A manual stereo-
plotter in the Division of
National Mapping,
Melbourne. The two
transparencies are
mounted in the carriers
under the shaded lamps
and the stereo-model is
viewed through the
eyepieces immediately in
front of the operator.
The "floating" mark is
moved by the control in
the operator's hand and
contour lines are
reproduced on the table
at bottom right.
A stereo-model is not a
model in tangible
form, but an optical
illusion seen by the
plotter operator as he looks through a dual eyepiece at the overlapping pair of
The operator really has a bird's eye view of a piece of country without actually being
there. He is able to see clearly natural and man-made features and is thus enabled to
ensure that they are shown accurately on maps prepared for printing.
All the hills and valleys can be seen clearly and this facilitates contouring. The operator
can control a pointer built into the viewing system and as he moves this along points of
equal elevation a slave arm (or pantograph) records the contour line on a table to one
side of the apparatus.
For the past 20 years the optical- mechanical system of plotting from aerial photographs,
or stereo-photogrammetry, has been considered a tremendous advance on the previously
more laborious and less accurate methods of map making.
Left: Contour lines and elevation points
reproduced by an automatic stereo-
The next 20 years should see an
equally impressive revolution in the
production of maps due to the
inevitable widespread introduction of
automation in photogrammetry.
Already Australia has felt the impact of
automation - the Division of National
Mapping introduced an automated
stereo-plotter in 1968.
This is still the only such piece of
equipment in this country and one of
the few operating on a day- to-day
basis in the world.
The equipment is a product of Swiss
and American research and like much
other modern surveying equipment it
makes extensive use of electronics.
In essence, it is a stereo-plotter which
still requires basic information derived
from ground surveys and in which a
pair of overlapping transparencies
need to be set up and adjusted with some human aid.
The operator of a manual stereo-plotter looks into the machine and produces original copy
for maps, showing contours and features such as roads and rivers by lines and smaller
individual features by symbols.
With an automatic plotter nobody needs to look into the machine - after the initial
adjustment - as it automatically produces orthophotographs and contours.
An orthophotograph is a true-to-scale plan of the terrain, reproducing with surprising
fidelity the features which can be observed on an untreated aerial photograph. An
ordinary aerial photograph contains distortions primarily due to variation in the height of
the terrain but due also to small tilts of the camera as each negative is exposed.
The transition to an orthophotograph with the simultaneous collection of contour
information is the nearest thing so far achieved to a map-making machine, for the ortho-
photograph will complement - and may for many purposes supersede - the line map as we
now know it.
Put together in mosaic form, these corrected photographs form a new map product - the
The automatic stereo-plotter presently in use relies on an electronic scanning system
similar to a television camera to observe the original transparencies and it reproduces the
images corrected for height displacement and tilt on a film enclosed in the machine.
Automatic stereo-plotter, showing the control cabinet (right), digitizing equipment
(left/front) and tape deck (left/background).
The machine can be set so that as its narrow scanner beam traverses the pair of
overlapping transparencies signals will be transmitted to record steps of 20 metres in the
elevation of the terrain.
The recordings emerge on the orthophoto negative as small segments of a contour line.
The segments are alternately thick and thin, giving positive identification of successive
contour intervals.
Colour film is used to enable the orthophoto detail and contour segments to be recorded
in different colours so that the contour segments can be filtered out for separate
Overleaf plate 1 shows an orthophoto with contour segments filtered out, while plate 2
shows a black and white reproduction direct from an orthophoto colour negative. The
separated contour segments are shown on their own in plate 3, but the discontinuities are
not serious. It is quite valid to edit these broken lines into the form shown in plate 4
because they are reproduced at a scale 2.5 times larger than the scale of the map for
which they are intended.
An alternative method of using the automatic stereoplotter for contour work is to set it to
pick up electronic signals at regular intervals as the scanner traverses.
These signals represent latitude, longitude and elevation at a number of points on a grid.
Data on these points are recorded in code on magnetic tape and in effect the equipment
"memorises" the shape of the terrain.
The information on the tape is fed to another type of automatic plotter. This machine
interprets the elevation data and its electronically controlled pen draws complete contour
lines on a sheet of paper designed to overlay an orthophoto.
If required, this equipment will
also put in selected spot elevations
and their heights in figures. An
example of this result is shown in
the illustration above.
This example is at a much larger
scale than usual and shows not
only contours but the values of the
height information from which
contours arc derived.
The grid of heights is suppressed
during production work. The
process is still in the development
stage in the Division of National
Mapping, but it promises
worthwhile economies where
dense contour patterns are
Map makers already recognise
orthophotographs as a base for
mapping at scales between 1 to
25,000 and 1 to 100,000 because
they produce a practical map in a
quarter of the time it would take to
produce a traditional line map.
For many other purposes - town
planning, civil engineering and
other work connected with
exploration and development -
they may be expected to have
increasing application.
Since they are capable of
production quickly and in true plan
form, orthophotographs and maps
must be recognised as one of the
basic tools in the hands of men
and women who will plan,
administer and carry out the
development of Australia during
the remaining decades of the 20th
* Mapping photography for Commonwealth purposes at present is in black and white,
but undoubtedly the problems presently inherent in the use and fidelity of colour film
for every day use will be overcome and there is likely to be more use of this medium
in the future. Colour film in the visible spectrum and in the infra-red area exposed at
relatively low altitudes already has wide acceptance and value for the assessment of
resources data by photo interpretation techniques.
The Division has taken the central role in a national mapping programme, not only
by contributing a large number of the maps required, but by co-ordinating the work
of the Royal Australian Army Survey Corps and the State Departments of Lands and
Survey in a national mapping effort.
Copyright © Commonwealth of Australia, Geoscience Australi, 1969.
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