Commission | Continued 
Instruments Recording Auxiliary Metric Data 
The Division of National Mapping has sponsored the development of an airborne laser 
profiler through the research facilities of the Commonwealth Department of Supply. 
The profiler developed is a continuous wave argon ion laser unit, which transmits to 
the ground a very narrow amplitude-modulated laser beam. The System is currently install- 
ed in a Grand Commander aircraft and is operated by a crew of three plus the pilot. 
Output from the unit consists of an ultra-violet chart record 6” wide and a continuous 
strip of 70 mm film. The two are related by means of a timing code which is simultaneous- 
ly superimposed on the edges of both. Two channels of the chart recorder are used for the 
timing code and the other five channels for the barometric reference trace, the height com- 
puter half scale shift, the aircraft roll measuring gyro, the frame camera event together 
with the coarse reading indicator and the terrain profile trace. 
The barometric reference unit comprises a sensitive differential pressure transducer 
and a stable pressure reference source. This enables it to record deviations above or be- 
low the selected isobaric surface and these values are applied as corrections at each pro- 
file point used for control. 
The half scale shift is used by the operator to position the trace in the centre of the 
chart, particularly over datum surfaces, thereby avoiding rapid scale changes over the full 
scale of the chart. Aircraft lateral tilt is recorded by the gyro and hence provides a 
correction to be applied to eliminate this effect. 
In addition, a Nikon 35 mm frame camera with a 50 mm lens is used to provide cover- 
age of a much wider strip of terrain than the strip camera and to assist in the transferring 
of the strip film on to the mapping photography. When operated, a pulse appears for about 
one second on the chart. It is used only in fairly featureless terrain. 
A drift meter is installed in the aircraft to determine the drift angle which can later be 
used in the computations to correct for inclination of the selected isobaric surface. 
Instruments and Methods of Navigation 
Beechcraft, North American Aero Commander, Grand Commander and Porter Pilatus 
aircraft are the main aircraft used for photography, operated by three man crews. Standard 
navigation equipment is used in most cases. Investigation by the Department of Civil Avi- 
ation and the Commonwealth Scientific and Industrial Research Organisation on the accur- 
acy of D.M.E. for precision position fixing indicate values of 1: 330. These investig- 
ations are unpublished. 
Doppler 72 equipment has proved satisfactory for navigation under difficult con- 
ditions. 
Dr. J.C. Trinder 
Commission Ill 
Most mapping organisations in Australia, both Government and Private, now rely on 
aero-triangulation and strip or block adjustments as a method of obtaining model control. 
Of some thirty organisations, approximately 25% are utilising stereo - comparators and 
analytical methods while the remainder mainly operate analogue equipment with a high pre- 
dominance of these using the ‘independent pairs’ numerical method. Numerical strip or 
block adjustment methods are used by many of the organisations, because of the readily 
available polynomial strip or block adjustment electronic computer programmes. The 
dramatic change to numerical techniques in this country is probably due to the big increase 
in the number of electronic computers now available within organisations or service 
bureaux.