In some cases, photography has been arranged for the search for oil in New
Guinea, whilst other photography has been recuired to detect areas in Australia where the
sinking of wells would reasonably ensure success,
H
Annexure A shows the coverage of aerial photography in Australia and New Guinea
as at 1st January 1560.
Annexure B shows the types of aircraft and aerial survey cameras acquired by
the various mapping agencies in Australia,
CONTROL
The National Mapping Council has approved of certain standards of accuracy as
regards geodetic and topographical surveys and map compilation which are adhered to by all
governmental mapping agencies,
This Council has also recommended that particular scales of mapping shall be
adopted for certain areas. Thus, in designing the National Geodetic Survey of Australia
and New Guinea, a primary system of control is being established which will generally
satisfy the ultimate mapping requirements.
Horizontal Control.
The geodetic control of Australia consists broadly of a chain of triangulation
and tellurometer traverse around the perimeter of the continent with several cross ties
and loops, This primary network of control is still in progress and eventually it is
envisaged that no point in Australia or New Guinea will be more than 100-150 miles from
this primary network,
The origin of this control is based on an astronomical value at the Sydney Obser-
vatory and all positions determined are placed on a Transverse Mercator projection in
zones 5 degrees wide,
At this stage only preliminary values of stations are available, the final values
eing deferred until such time as the primary network has been completed and an overall
1d justment has taken place,
As it is difficult to keep the primary control abreast of areas where mapping is
required for investigation and possible development, it is necessary, vhere no triangulation
or traverse exists, to make extensive use of the astronomical fixation for the control.of
1:250,000 mapping, To à minor degree SHORAN has also been used for this purpose,
Fortunately to date, ir the developed areas where medium seale mapping is re-
quired, a primary network of control is vithin a reasonable distance whereby vith normal
survey methods this control ean be extended to cover the area to be mapped.
Vertical Control
Vertical control of first order accuracy has, unfortunately, not kept abreast
with the horizontal control, but the reason is undoubtedly the ready availability of good
railway and engineering levels throughout the more intensely developed areas sre the
majority of mapping to date has taken place, These levels have usually been found suf-
ficient as a basis for mapping operations and to control any error that may have developed
in elevations carried forward in the course of triangulations or traverse,
Most State Lands Departments are currently establishing a framework of geodetic
levels but progress to date has been slow, Although each depa ent is working indepen-
dently, it is the aim to ultimately co-ordinate this activity on a National Datum,
Ï
LI
When heights for mapping control are required in areas where no primary control
exists, several methods have been employed, These include barometric heighting. which
are corrected to regular readings made at surroundings meteorological stations, barometric
4
eighting by fixed wing aireraft and helieopter and the estimation of stream gradients
within the boundaries of given spot heights,
MAPPING ACTIVITIES BY VARIOUS ORGANISATIONS
It has been decided that the general topographical mapping requirements of Aust-
ralia can adequately be met by the following scales i=
>
: 250,000 or 1:253,440 with 250 feet contour interval
1:63,360 or 1:50,000 with 50 feet contour interval
:31,680 with 25 feet contour interval.
With reference to Annexure C, which shows the position of various types of
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