The practical training is not aimed at
attaining proficiency, but a working knowledge
level. It clears a threshold, which is
normally associated with flying and aerial
photography.
Since 1978 nearly 200 exercise flights
have been executed, training about 200
students. More than 90 % of the participants
proved to be able to produce very acceptable
photographs, particularly in the second
exercise flight. An important factor is the
use of automatic exposure (shutter priority)
single lens reflex cameras with a motor drive,
allowing full concentration on detecting and
photographing the target areas.
A relative small number of participants
applied this training in their work situation.
Major problems are the security clearances in
many countries, and possibly resistance
against new tasks considered to be alien to
the traditional planning organization.
The ITC Urban Survey departmental staff
applied the technique to provide up-to-date
data for a number of research projects in the
Netherlands, Cyprus, Kenya, Sri Lanka,
Suriname, and Tanzania. In a few cases it was
allowed to take off an aircraft door,
providing less constraints in camera pointing.
In these cases hand-held, near-vertical
photography was realized too (Fig.3).
7
AIR PHOTOS, MAPS, AND GEO-INFORMATION SYSTEMS FOR URBAN PLANNERS
An environment in which the map producer
and consumer (i.c. the urban planner in a
developing country) are closely linked, is
very desirable as it can ensure the so much
needed specific products and fast production.
Such a situation could be created when the
data acquisition (aerial photography, ground
control measurements, and additional data
collection), photo interpretation, and mapping
are executed by and within the urban planning
organization.
Such an in-house mini-survey department
should not imitate large, specialized survey
organizations, but concentrate on what is
essential to its own organization: fast
production of aerial photographs, air photo
interpretations, field checks, field
measurements, and maps. The investments, the
running costs, as well as the required skills
of operators, should be limited to suit that
purpose, so that this mini-survey department
can be run on the basis of the regular budget
of the organization.
In such a context, ultralight or light
airplanes adapted to aerial photography, and
small format cameras can play an essential
role to provide low-cost and up-to-date air
photos of project areas. Moreover, appropiate
low-cost, approximate mapping methods and
techniques have to be introduced to make such
a system feasible.
Existing services as an in-house
photographic laboratory, ground survey team,
mapping office, and draftsmen, of course
should be utilized and integrated into such a
system. External commercial services can
provide, for instance, additional map printing
facilities.
The quality of a thematic map is to a very
large extent determined by the theaatic
accuracy: the correct classification of
objects and elements. Also, when considering
the way maps are used in a planning
environment, the importance of the metric
accuracy is quite relative. In many cases
sketchmaps (without geodetic control) will be
acceptable. For specific applications, mostly
at the engineering level (implementation of
infrastructure constructions) an approximate
map may be upgraded by local measurements
through a precision method as a ground survey.
The geo-information system part already
appears to be fairly well developed: systems
that at least claim to be good are abundant on
the commercial and semi-commercial markets.
The essential link with the front end, the air
photo and map data acquisition part, however,
still seems to be weak, as long as low-cost
mapping systems are considered (for cities in
developing countries). The experiences with
low-cost aerial photography systems in
projects supported by ITC in China, India, and
Indonesia, demonstrate the feasibility of such
systems to deliver the required photos
economically and timely.
The main problem now seems to be the
conceptual (not the technical) development of
a low-cost mapping technique from small format
aerial photography. As on one hand the
precision requirements are not very high, and
on the other hand low-cost mapping systems are
feasible (even including microcomputer based
analytical plotters), prospects are favorable
(Warner,1989). Such a decentralized system, if
well designed, could also provide important
inputs into an information system for urban
planning and management.
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