The series relates to the functions of survey and mapping for Commonwealth
Government purposes and Earth Sciences. The recording agency was responsible
for the systematic geological and geophysical mapping
of Australia
for mineral exploration and other purposes. A892 consists of black and white diapositive transparencies on film or glass plates. Each
item shows some or all of the following data: location, run number, negative
number, scale, date, flight time, altitude, frame number. The frame and
negative numbers are not necessarily the same.
There are surveys for: all states, and the Northern
Territory, of Australia;
Papua New Guinea.
A separate series (A896) was created for the Australian Capital Territory. Areas surveyed
include: Norseman – Pioneer B; Pioneer B – Mount Edwards; Mount Edwards – Alan
Hill; Alan Hill – Kalgoorlie; Kalgoorlie – Red Hill; Darwin – Mt Isa; Townsville – Mt Isa; Eucla;
Kiama; Kongwirra; Wanneroo; and Williamstown.
Projects include: aerodromes and airports (e.g. Albury and Pearce Aerodromes;
Gin Gin Satellite Aerodrome; Darwin RAAF; Alice
Springs, Brisbane, Darwin, Sydney and Tullamarine airports; and, Lae airstrip in Papua New Guinea); military projects (e.g.
Northam Army Camp, Balcombe Army Project, Enogerra
Barracks); and, stores projects and communications installations.
From
1961, aerial photographic surveys of Australia were conducted for the agency by private
contractors. The exception was when another government agency was known to be
undertaking aerial survey work and arrangements were made to acquire copies of
the negatives. Aerial survey negatives were processed to supply: a positive,
for preparatory checking and scanning; and, a diapositive
(positive transparency) used for the purpose of photogrammetric
restitution.
Photogrammetry is a remote sensing technology that
enables two dimensional images of three dimensional objects to be used to
reconstruct accurate models of the original three dimensional scenes. Two or
more images are taken from adjacent positions. Measurements are made in the
images and common points identified in each image. Lines of sight (or rays) can
then be plotted using the location the images were taken from and the
identified points on the images. Triangulating the rays reconstructs the
three-dimensional location of the identified points. The photogrammetric
restitution process was a plotting instrument that, when set, reproduced maps
and profiles from the diapositives, creating an
optical stereoscopic model of the photographed terrain. These stereoscopic
models were used to create accurate maps and survey plans and multiple printed
copies could be produced from one original.
Sources
Series documentation
1 2 3
Photogrammetry.com, ‘What is Photogrammetry?’, downloaded 5 May 2009 from http://www.123photogrammetry.com/photogrammetry.html
Geoscience Australia website, downloaded 5 May
2009, http://www.ga.gov.au/about-us/history.jsp
Wikipedia.org, ‘Photogrammetry’, downloaded 5 May 2009 from http://en.wikipedia.org/wiki/Photogrammetry