Using this type of arrangement, it seems un- 
necessary to have accurate knowledge of the 
orientation parameters of the image acquisi- 
tion system. The imagery was of quite accept- 
able quality and residual parallaxes after 
relative orientation were of the order of 
eighty micrometres. The experienced photogram- 
metric instrument operators who performed the 
observation work felt quite comfortable in 
that work and confident of the repeatability 
of their observations. 
In Fig 4, a formline plotis reproduced of the 
pavement sample of which Fig 3 shows a stereo- 
gram. The formline interval is half a milli- 
metre on the faces of individual pieces of 
aggregate and one millimetre elsewhere. This 
formline plot was produced of the WILD A.10 
plotting table at a magnification of three 
diameters,but has been fairdrawn and repro- 
duced at a reduced format for publication. 
The original pencil plot and the fairdrawn 
sheet are exhibited for the benefit of those 
attending the presentation of this paper at 
this conference, as is the pavement sample 
portrayed and a gridplate replica. 
Also observed in the relevant stereogram were 
three sections of this pavement sample. These 
were observed directly in the WILD A.10 and 
recorded on the plotting table by interchang- 
ing the Y and Z drives in the instrument. 
Reproductions of these sections are contained 
in Fig 5. The locations of these sections in 
the pavement sample are shown in Fig 4. 
The objective of this phase of this research 
and development project was to demonstrate 
that textures of pavements are capable of 
portrayal in units of the order of magnitude 
of millimetres, without needs to acquire spe- 
cial image-acquisition systems. Certainly, 
the resources of the CSIRO National Measure- 
ment Laboratory photographic section were 
available for this work and those facilities 
(and the expertise of relevant personnel) 
were vital in developing a practicable app- 
roach to these aspects of the work. It is re- 
levant to note that many other attempts were 
made using other configurations of image 
acquisition systems before success was achie- 
ved with this particular system. 
CALIBRATION OF OBSERVATION SYSTEM 
Calibration Body 
Having demonstrated successfully that textu- 
res may be portrayed satisfactorily at these 
Scales, the significance of the magnitudes 
portrayed must be assessed. As in topographic 
photogrammetry, the appropriate approach 
seemed to be to relate observations to control 
data both in planimetry and in height. The 
calibration body used for this purpose was the 
gridplate replica and the gaugeblock arrange- 
ments of which mention has already been made. 
With no exact knowledge of the elements of 
inner orientation of the image acquisition 
System, it had to be accepted that the photo- 
grammetric restitution would be affine, that 
is that the scale in height would be different 
from the scale in planimetry, in the stereo- 
Scopic model in the restitution instrument. 
But the dimensions of the calibration body 
are known within smaller tolerances than it 
would be expected to achieve in the photogram- 
metric measurements with the A.10. 
  
SECTION C-C 
  
SECTION B-B 
SECTION A-A 
    
SCALE IN MILLIMETRES 
o 5 10 20 
30 40 so 
Fig 5 Reproductions of the three sections 
of the pavement sample illustrated in 
Figs 3 & 4 
105