48 
ANNEXURE F 
PRELIMINARY REPORT ON ANALYTICAL AERO-TRIANGULATION IN TASMANIA 
M, T. Noonan, Senior Computer 
Department of Lands, Tasmania 
Introduction 
The following is an outline of the method of analytical aero-tpriangulation prac- 
tised in Tasmania and briefly summarises the results obtained both as regards accuracy and 
time. 
The procedure is generally similar to that described by Mr D, W, G, Arthur in "A 
Stereocomparator Technique for Aerial Triangulation" Ordnance Survey Professional Paper, 
New Series No, 20, H,M.S.O. 
Some alterations have been made to suit our requirements and a full description 
of the method is now in course of preparation which will also include results obtained on 
check points scattered throughout a test -area, 
The camera used is & 6" Williamson Eagle IX fitted with a 1 cm Reseau Register 
Glass, 
An area usually consisting of ! map sheets is flown with 5 Key Strips. Three 
groups of ground control are obtained for each Key Strip, one group at each end and one in 
the centre, While each group will have one horizontal control point, it is desirable that 
one group should have two such points, 
Ground co-ordinates of selected pass points common to both the Key and Cross 
Strips are computed and used for the ad justment of the individual cross strips to the ground 
co-ordinate system, 
Summary or Procedure 
  
d. All points to be observed are marked in the Stereocomparator on glass diapositives 
with a fine pricker, such mark being approximately .03 mm in diameter, 
2. For an overlap six minor control points are selected and o^served in the positions 
A.P.B. and A'!'P'B' as shown in fig. 4. 
When difficulty is found in obtaining a reliable point it is necessary to observe 
the points in pairs to maintain accuracy. 
3. After observation in the Comparator corrections are made for film and lens dis- 
tortion. The photo co-ordinates are then tabulated and forwarded to the University of 
N,S,W. where the stereogram solution is carried out on the UTECOM electronic computer. 
This solution gives the relative orientation, the base components between suc- 
cessive perspective centres, scale factors and residual K's for the six minor control points. 
He The results are checked by our staff and where the residual 'K'! is greater than 
0.02 mms.the point is re-observed, Should the result still be unsatisfactory, a new' point 
is observed, 
Scale factors for extra points such as additional ground control, tie points etc, 
are then rapidly determined with a desk computer. 
5. After solution of the Absolute Orientation for each control areathe strip scale 
factors are computed, all stereograms are levelled and the strip is then fitted to the 
three ground control areas by means of a second order conformal transformation, The 
horizontal ground co-ordinates of all tie points with neighbouring strips are then com- 
puted. 
6, Using the vertical control points a Flying Height for each photograph is derived 
and from these, elevations are obtained for all tie points, 
. All cross strips are treated as above and a graphical block adjustment similar to 
that of Dr Bandenberger is carried out in order to make the block homogeneous, 
8, The co-ordinates and elevations of all minor control points are determined and 
the data for orienting the diapositives in the Wild plotters is tabulated,