Full text: Remote sensing for resources development and environmental management (Vol. 2)

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 
Application of stereo-terrestrial photogrammetric technique 
to varied geoscientific investigations 
Geological Survey of India 
ABSTRACT : Stereo-terrestrial photogrammetry provides distinct advantages over conventional techniques in 
large scale topographic and thematic mapping of selected areas. During last six years this technique has 
been advantageously applied to various geoscientific investigations in the Geological Survey of India, impor 
tant amongst them being the Nilgiris landslide investigation, Tamil Nadu; escarpment slope mapping of Supa 
Dam, Karnataka; mapping of Coconut Island, off west coast, Karnataka; and mapping of a glacier in north-west 
The methodology consisted of taking terrestrial stereo-pairs from 'UMK-100' Camera; surveying of control 
points with the help a theodolite or 'Distomat' and plotting of details on the Unviersal Anologue Stereo-plo 
tter 'Topocart'. Topographic and photo-interpreted thematic maps of these areas were prepared on scales 
between 1:500 and 1:2000, except for the glacier which was covered on 1:5000 scale. The experience obtained 
in applying this technique in diverse terrains has helped in gradually selecting the most suitable methodol 
Results clearly demonstrate the potential of this advanced technique in large scale mapping, for a compre 
hensive evaluation of selected areas with speed, economy and precision. Further, the technique offers exci 
ting possibilities of digital terrain modelling for multitheme mapping by making use of 'Analytical Stereo- 
Geoscientific investigations of project areas requi 
re preparation of large scale topographic base 
map and relevant thematic maps of the area. Norma 
lly, this work is being carried out with the help 
of conventional plane table or theodolite survey 
Aerial photogrammetric mapping has already been 
established as a powerful tool for preparation of 
topogrphic base maps with speed, economy and preci 
sion, and the potential of photo-interpretation 
technique is increasingly being exploited for thema 
tic mapping. 
Terrestrial photogrammetry permits acqusition 
of controlled stereo-photographs of selected areas 
at the desired time. The stereo-pairs are used 
for the simultaneous preparation of large scale 
topographic base map and relevant thematic maps 
of the area. Further, computer assisted analytical 
stereo-plotters, which are making a breakthrough 
in photogrammetric mapping, provide scope for simu 
ltaneous digitization of topographic and thematic 
data of the area. This in turn would make morphome 
tric and thematic mapping, either separately or 
in combination an easy proposition. 
Terrestrial photogrammetry was introduced in 
Geological Survey of India in 1978. Since then 
this technique has been advantageously applied 
to a variety of geoscientific projects involving 
diverse terrains, varying from Coastal tracts to 
high mountaneous regions. Some of the important 
investigations in which this technique has been 
applied include Nilgiris landslide investigation, 
Tamil Nadu; escarpment slope mapping of Supa Dam, 
Karnataka; geo-environmental study of Coconut Is 
land, off West Coast, Karnataka; and mapping of 
a glacier in Northwest Himalayas. 
The experience obtained while applying the tech 
nique in diverse terrains has progressively helped 
in adopting the most suitable methodology. 
The technique of terrestrial photogrammetry invol 
ves establishment and survey of four to five control 
points in the area; photography for obtaining ste 
reo-pairs with the help of a terrestrial phorogra- 
mmetric Camera unit; and finally map preparation 
in the laboratory on a stereo-plotter. 
In the present surveys, a wide angle terrestrial 
photogrammetric plate Camera 'UMK-100' (plate size 
13 cm x 18 cm) of 100 mm focal length was used 
for photography. Survey of control points was 
intially done with help of a theodolite and subse 
quently by an electronic distance measuring unit 
Distomat. Map preparation was undertaken on the 
analogue stereo-plotter Topocart. 
2.1 Control point survey and establishment 
Establishment and survey of control points in 
the area is an important part of the photograpmme- 
tric survey. For an expeditious and accurate survey 
of the control points an electronic distance measu 
ring unit Distomat has been found to be highly 
convenient and handy. The coordinates of the surve 
yed points can be obtained instantaneously in 
the field. 
In case of present surveys two different types 
of orientation systems were used, one for the 
Camera and the other for the Distomat. However, 
if the Camera and the Distomat can be mounted 
on the same orientation system then the field 
unit becomes quite compact. It is particularly 
significant if the unit has to be transported 
on head loads for survey in remote inaccessible 
During application of the technique in different 
areas various objects have been tried as control 
points. Ultimately, it has been found that white 
painted circles, of appropriate dimensions (Manual

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