2.0 THE POTENTIAL FOR SMALL FORMAT DIAPOSITIVES 
Aerial photography produced for mapping is used for many other purposes by 
people from various disciplines such as foresters, town planners, 
engineers, etc. Mostly the information extracted by these people is by 
means of approximate techniques since they seldom have access to accurate 
equipment nor do they have the time to become skilled at using mechanical 
analogue equipment. In addition it is usual for maps to be reviewed on 
say a ten to fifteen year cycle, but photography is to be taken on say a 
two to three year cycle so that the photography represents current 
information. 
A mapping organization could cheaply produce a microfilm data base for an 
area in addition to their normal products. Such a data base would consist 
of reduced diapositives together with a diskette of orientation parameters 
computed from the block adjustment. in this way the the organization 
would be making their expertise more readily available, and users of 
photogrammetric data would have direct access to more accurate 
information. 
3.0 INITIAL MEASUREMENTS 
The Central Mapping Authority of New South Wales maintains a 
photogrammetric test range in the Bathurst Town Area. The co-ordinates of 
over 60 natural features have been measured by conventional surveying 
techniques and photography at various scales has been taken of the area. 
Negatives from a typical stereo-pair were selected and rephotographed 
using a Hassablad camera fitted with a 100 mm copying lens. The camera 
was mounted on a tripod, the negative on an illuminated table, and the 
principal axis of the camera was set normal to the negative by first 
pointing to a mirror placed on top of the negative. When the photographs 
were taken the mirror was replaced by a glass grid plate with the grid 
squares in contact with the emulsion of the negative. 
Photography was on Kodak Technical Pan film 2415 (ESTAR-AH Base) and it 
was processed to achieve maximum resolution according to the manufacturers 
instructions. 
The original photography was at a flying height of 2530 metres with an 80% 
overiap giving an air base of 1096 metres. 
Initial measurements of the fiducial marks were made in the MPS to 
determine the reduction scale. This value was used to compute fiducial 
co-ordinates and the effective focal length of the reduced diapositives 
using data from the aerial camera calibration certificate. 
An orientation was then performed on the MPS and after misidentified 
points were removed, the standard errors in X, y and z were about 0.3 
metres. 
The photos were then measured using the MPS in stereocomparator mode to 
record plate co-ordinates of 52 points as well as the camera fiducials. 
The camera fiducials were measured twice to check the precision of 
pointing and this was inside 4 microns. 
24