Photogrammetry:
a solution looking for opportunities
by prof. P. F. Dale, MA., PhD., FRICS., FlnstCES, Head of Department of Land
Surveying, University of East London.
SAMENVATTING
Fotogrammetrie: een oplossing die kansen zoekt
Fotogrammetrie staat op een kruispunt. De technische ontwikkeling van analytische instrumenten heeft
een hoogtepunt bereikt; de grootste doorbraak die wordt verwacht ligt in het vermogen om het menselijk
brein te evenaren bij het interpreteren van patronen en beelden. Toepassingen, zoals bij industriële
metingen, zullen waarschijnlijk nog wel verder ontwikkelen, maar in de traditionele gebieden zoals
kartering, zijn er nog belangrijke sociale en omgevingsfactoren die de fotogrammeter nader dient te be
schouwen. Met name de rol van de fotogrammetrie in de vastgoedsector moet worden versterkt met een
meer omvattende en actuele kartering, vooral in bebouwd gebied. Luchtfoto's moeten toegankelijker wor
den in ontwikkelingslanden en daartoe moet de fotogrammeter meer politiek dan technisch georiënteerd
zijn. Dit artikel kijkt naar de fotogrammetrie vanuit een karterings- en informatie-wetenschappelijk stand
punt en stelt de vraag wat de fotogrammeter kan bijdragen aan het oplossen van problemen in de wereld.
SUMMARY
Photogrammetry is at a cross-roads. Technical developments have
reached a peak and although more research and development is
needed in the refinement of analytical devices, the major technical
breakthrough that is awaited is in mimicking the ability of the human
brain to interpret patterns and images. Applications, for instance in
industrial metrology, are likely to grow but in the traditional fields of
surveying and mapping there are significant social and environ
mental problems that the photogrammetrist needs to address, in
particular the rote of photogrammetry in land management needs to
be reinforced and more extensive and up-to-date mapping provided,
especially in urban areas. More open access to aerial photography
is needed in developing countries and to achieve this the photogram
metrist needs to be more of a politician than a technician. This paper
looks at photogrammetry from a mapping and information science
perspective and asks what the photogrammetrist can do to ameliora
te the problems of the world.
Technology
Underlying this paper is an assumption that photogram
metry is a mass production tool capable of delivering a
wide range of accurate and precise geometric measure
ments. The quality of these measurements depends
fundamentally on the price that is paid since this deter
mines the type of equipment that can be used and the
capabilities of those who operate it. Quality of information
is however another matter and although there are specific
skills in photo-interpretation especially within military
circles, the general standard and accuracy of image inter
pretation does not match the quality of geometric meas
urement. Many training courses in photogrammetry
spend significantly more time studying geometry and the
operation of stereo-plotting machines than they do on
image interpretation.
This lack of concern for the classification of images is also
apparent in the study of remote sensing which has sig
nally failed to produce consistently reliable information;
its champions still present best-case scenarios rather
than general levels of accuracy in their interpretation of
the environment. Any discipline that can announce that
its assessments were wrong by 50% as happened in
1990 regarding the rate of depletion of the world's tropical
forests should refrain from using hyperbole. Yet claims
abound that are not sustainable under normal operating
conditions. Parallel 'hype' has been coming from the
Geographic Information Systems (GISs) community that
has proved even more damaging to clients who have
found the price of data and the problems of implemen
tation much more severe than they had been led to
believe.
Photogrammetry is of course a more mature discipline
and its protagonists no longer have to defend their credi
bility. One can only hope that in due course both the
remote sensing and GIS-communities will reach the same
balanced view and will no longer over-sell their products.
But whereas photogrammetry has, by and large, solved
its measurement science problems there are a number of
areas where there are challenges that still need to be
addressed.
Urban expansion
Consider for example the plight of many cities in the third
world. Many of these are growing at a rate of between
5% and 7% per annum. Lahore in Pakistan for example
is growing at 150,000 people per year (averaged over
twenty years), Greater Cairo at 270,000, Jakarta at
325,000 and Mexico City at 550,000 people per year. To
day there are 29 cities with a population of over 5 million
people; by the year 2000 there will be double this number,
led by Mexico City with an estimated 31 million inhabi
tants. This growth stems in part from the better facilities
that exist within cities such as access to health services
and the control of water quality that result in higher sur
vival rates in Indonesia for example, for every 1000 live
births, there are 60 child deaths in urban areas but 96 in
rural an increase of 60%. The urban expansion is also
in part due to migration away from the rural areas where
fuel for cooking and heating is increasingly hard to obtain
and where drought or civil disturbances may make a
sustainable existence impossible. The influx into cities
usually overwhelms the authorities who are unable to
cope, leaving market forces and the informal sector to
solve many of the resulting problems. Thus cities grow in
an unplanned and uncontrolled fashion.
To bring some semblance of order, many political and
administrative actions are needed there is no quick
and easy solution. Nevertheless a major strategic compo
nent in any development must be good land information
through which problems can be clearly identified and
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