A REVIEW OF CLOSE-RANGE ENGINEERING PHOTOGRAMMETRY 
been easy to apply away from the stability of 
laboratory surroundings. : 
An area in which commercial photogram 
metric companies have been able to contrib- 
ute to the application of close-range tech- 
niques is that of dams and rock outcrops, both 
natural and excavated. Fairey Surveys Ltd. 
carried out a survey of Edinburgh Castle 
Rock (Cheffins and Rushton, 1970) in 1969 
using a Wild RC5A camera, and since that 
time several other companies have been in- 
volved in similar surveys in places as widely 
separated as Muckle Flugga in the Shetland 
Isles and Plymouth in Devon (Figure 1). The 
engineering contractors need these surveys 
because of the instability of the rock surfaces. 
Rock bolting, construction of retaining walls, 
rock blasting and related safety aspects, and 
prefabrication of structures all require the in- 
formation provided by, typically, a 1:50 scale 
survey with contours or isometrons* related 
to a vertical datum plane. A dam is a structure 
of similar size and its behaviour is of the ut- 
most concern; photogrammetric surveys of 
dams have been reported in the United King- 
dom and elsewhere. The Building Research 
Station and Hunting Surveys Ltd. were 
jointly responsible for the photogrammetric 
study of the constructional displacements of 
the rockfill dam at Llyn Brianne in mid-Wales 
(Moore, 1973). The dam is 90 m high and 
200 m wide. A Wild P30 phototheodolite was 
used to provide stereoscopic coverage, at 
eight different stages of construction, of both 
upstream and downstream shoulders. 
Ground control was established on the valley 
sides, together with 80 targeted points at var- 
ious levels on the dam. Three dimensional 
co-ordinates were required of these pre- 
marked points and in fact three dimensional 
displacements were determined to an aver- 
age accuracy of 0.05 m. Profile lines through 
the dam also were obtained. Brandenberger 
and Erez (1972) and Brandenberger (1974) 
also have reported on dam surveys which in- 
volved photogrammetric techniques. Bran- 
denberger achieved greater accuracies at 
Outardes, Quebec than Moore reported from 
Wales but of course so much depends on the 
configuration of the site and on the equip- 
ment which happens to be available for the 
survey. 
The Building Research Station has also 
* O.C. Gibbins has used the term isometron for 
lines which pass through points having the same 
depth or distance from a vertical plane. See Gib- 
bins, O.C., 1970. Searching for hydroelectric 
power schemes in Tasmania with special reference 
to the Dove River. Cartography, 7(2): 59-68. 
59 
conducted a photogrammetric study of joint 
influence on weathering of steep chalk faces; 
it has determined the joint disposition and 
material volume after slide failure in Oxford 
Clay; and it has monitored a deep, steep rock 
cutting on the Trans-Pennine (M62) motor- 
way. 
An interesting variation on surveys of this 
type and magnitude of structure is reported 
from Poland (Butowtt et al., 1974) where 
studies of erosion of a number of scarps on the 
banks of the River Vistula have been carried 
out. A modified Fairchild air survey camera 
(cf. Cheffins and Rushton, 1970), carried on a 
launch, was used for photography, and con- 
toured plots and profiles were derived from 
the photography. 
Collaboration between the Institute of 
Hydrology and The City University has led to 
the use of terrestrial photogrammetry in an 
analysis of snow distribution (Blyth et al., 
1974). A research catchment on the eastern 
slopes of Pumlumon Fawr in Wales con- 
tained a test area, 300 m x 100 m in extent and 
ranging in height between 460 m and 525 m. 
This site was photographed, both free of 
snow and under snow cover of about 100 mm 
depth, from each end of a 100 m base. En- 
couraging results for the determination of 
snow depth when compared with site checks 
may lead to the use of photogrammetric 
monitoring in connexion with provision of 
hydrological data for use in flood warning 
systems. Photogrammetry may also be used 
in an examination ofthe physical processes of 
snowmelt. 
Fairey Surveys Ltd. have, over the years, 
shown a refreshing readiness to attempt the 
solution of a variety of measurement prob- 
lems. Reference already has been made to 
Edinburgh Castle Rock (Cheffins and 
Rushton, 1970) and, in a recent paper, Chef- 
fins (1975) has described other applications 
of non-topographic photogrammetry in 
which his company has been involved. Two 
of the applications which are described in 
that paper are of interest at this juncture. The 
first concerned the determination of distor- 
tions in the area adjacentto the static vent ofa 
BAC 1-11 aircraft. Close-range stereometric 
photography of an area just in excess of 1 m? 
was analysed to provide a regular grid of 
depth values ofthe area of interest. The cam- 
eras (f=150 mm) were about 1.5 m away from 
the fuselage and the overall repeatability of 
depth measurements from four different sets 
of photography of the same subject, when an- 
alysed photogrammetrically, was + 0.36 mm 
root mean square error (or 1 part in 4200 of 
the object distance).