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OPERATIONAL EXPERIENCES OF DIGITAL PHOTOGRAMMETRIC SYSTEMS 
Martin J. Smith and Douglas G. Smith 
Institute of Engineering Surveying and Space Geodesy 
The University of Nottingham 
University Park 
Nottingham 
United Kingdom 
Commission Il Working Group III 
KEY WORDS: Digital, Experience, DEM/DTM Comparison, Parameters, Urban, Rural. 
ABSTRACT: 
The Institute of Engineering Surveying and Space Geodes 
British Geological Survey (BGS) and the National Remote S 
y (IESSG) is working on a collaborative project with the 
ensing Centre Limited (NRSC) Airphoto Group. During this 
project experience of using the Intergraph ImageStation and ERDAS OrthoMAX and SoftPlotter is being obtained. This 
paper discusses some of the more important issues of this experience before concentrating on the quality aspects 
concerning the automatic generation of Digital Elevation Models (DEMs) which are available from the Systems. The 
effects of changing DEM parameter settings highlight the potential strengths and weaknesses of such automatic 
procedures. 
1. INTRODUCTION 
The latest developments in hardware and software 
technology have opened up a new area for 
photogrammetrists in the last few years. The advances in 
digital photogrammetry now mean that it is possible to 
view scanned aerial photography in stereo at high 
resolution and carry out interactive on-screen 
interpretation and digitization. Software technology has 
led to the ability to automatically identify control points, 
generate digital elevation models and produce orthophoto 
products, leading to a potential efficiency revolution in the 
photogrammetric workplace. Associated interest has 
been stimulated in areas outside of photogrammetry with 
the possible benefits of these digital products creating a 
new interest in aerial photography. 
The success of digital systems will only be fulfilled if it can 
be seen that the financial outlay will be recompensed by 
an improvement in workflow, both in time and efficiency. 
The Institute of Engineering Surveying and Space 
Geodesy (IESSG) is working on a collaborative project in 
digital photogrammetry with the British Geological Survey 
(BGS) and the National Remote Sensing Centre Ltd. 
(NRSC) Airphoto Group. The research involves the use of 
the Intergraph ImageStation at BGS and ERDAS Imagine 
OrthoMAX and SoftPlotter at NRSC. This paper will 
provide a highlight of the work undertaken so far and 
present experiences obtained whilst carrying out the 
research. 
2. BACKGROUND 
The three institutions involved in the project have differing 
backgrounds in photogrammetry, but have been brought 
together by the development of digital techniques. The 
IESSG is involved with the teaching of traditional 
photogrammetry alongside research into current fields, 
357 
making use of its Leica SD2000 analytical plotter. Further 
analytical experience, including semi-automatic DEM 
generation, has taken place on a Zeiss P3 at NRSC. BGS 
have moved into the field of photogrammetry relatively 
recently with the acquisition of an Intergraph 
ImageStation. Their background in remote sensing 
helped identify digital photogrammetry as a potential aid 
to geological interpretation and geographical and 
environmental analysis. With respect to geological 
interpretation, their aim was to increase productivity, 
reduce costs and to provide mapping geologists with the 
opportunity to spend increased time on areas which are 
particularly problematic (Tragheim and Westhead, 1996). 
Fundamental to the interpretation and analysis is the use 
of Digital Elevation Models (DEMs) to aid the task 
directly, by producing orthophotos or, in combination with 
the orthophoto, perspective views. NRSC Airphoto Group 
are a more traditional mapping establishment who have 
made the step into digital photogrammetry in an attempt 
to increase productivity and establish new product areas. 
At present they are concerned with orthophoto products, 
of which DEM acquisition is fundamental. 
Consideration of the interests of BGS and NRSC, coupled 
with early trials on the instrumentation, indicated the 
importance of DEMs, and more particularly their 
accuracy. The potential of digital systems is clearly 
associated with their ability to perform traditional 
photogrammetric tasks automatically. This paper aims to 
present some experiences of using two digital 
photogrammetric systems. 
3. EARLY EXPERIENCES 
Prior to undertaking the specific research project, 
preliminary training periods were undertaken on both 
systems to gain general experience and to identify 
benefits and limitations. 
International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B2. Vienna 1996