20 16 12 8 : 4 
Fıc.15. The block of 20 samples which appears 
in Fig. 14 reproduced with overlying roughness 
profiles. The profile data were digitised and 
computer plotted. The information on roughness 
was used to determine suitable materials for the 
two-dimensional open pit excavations. 
parallax techniques which Wickens and Barton 
(1971) also explained (Figure 16). This work 
formed part of the experimental background 
to geological joint mappingofopen pit mines. 
Practical photogrammetric techniques were 
evolved and modified for use in a mine situa- 
tion. They were based on the Wild P30 photo- 
theodolite equipment (Ross-Brown and At- 
kinson , 1972). Analysis ofthe survey photog- 
raphy (Figure 17), some of which has been car- 
ried out by a commercial company (Meridian 
Airmaps Ltd.), involves a conventional rela- 
tive orientation in a plotting instrument but 
absolute orientation is a computational pro- 
cedure. This makes it possible to employ 
principal distances and photographic tilts 
which some plotting instruments could not 
accept. The orientation of each joint is deter- 
mined by four points whose co-ordinates are 
PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1976 
  
tion. The measurement of displacements 
around an excavation was carried out by false 
parallax methods. Movements of 0.1 mm were 
detected. 
observed and recorded in the steromodel. 
Details of geological interpretation and joint 
selection, together with case histories and ac- 
curacies, will be found in Ross-Brown et al. 
(1973). The co-ordinates of the points on the 
joints are used in a subsequent plane fitting 
procedure. This involves setting up the nor- 
mal equations for a linear least squares fit and 
solving these normal equations. From the re- 
sulting symmetric coefficient matrix the 
three direction cosines may be determined 
and subsequently transformed by means of 
the transformation matrix previously ob- 
tained. The planes may then be described in 
terms of dip and dip direction or azimuth. 
A related development of this application 
has occurred in work carried out by the 
Transport and Road Research Laboratory 
with a Wild P32 in Colombia (Kempson and 
Heath, 1972). The Laboratory investigated a 
number of landslides in order to determine 
slope angles, sizes of cracks and fissures, and 
earth volumes. Analysis of the photography 
was undertaken by Meridian Airmaps Ltd. 
CONCLUSIONS AND SUGGESTIONS 
There is a great deal of activity and interest 
in engineering photogrammetry although 
much of the work is being carried out in a 
research context. When that research work 
reaches a conclusion, there may be no further 
employment for the photogrammetric tech- 
niques which have been used as a measuring 
tool. Other projects, though entirely com- 
mercial, are often unusual or “one off” and 
design, erection, setting out survey, control 
or monitoring are peculiar to that project. In 
cases such as these, there is still an enormous 
need for education of the engineer so that he 
is aware of the full possibilities of photo-