Low-cost aerial photography and mapping for urban projects 
Paul Hofstee Department of Urban Survey and Human Settlement Analysis 
International Institute for Aerospace Survey and Earth Sciences (ITC) 
P.0. Box 6 7500 AA Enschede Netherlands 
□Os 
paper ISPRS Comnission VII Symposium, 17-21 Sept 1990, Victoria, B.C., Canada 
ABSTRACT 
The suitability of low-cost (small format) 
aerial photography as a survey tool for a 
number of urban planning applications in 
developing countries, where up-to-date 
information is scarce, and resources are 
limited, is discussed. The technique is 
conceived to be suited for relatively small 
areas, where no precision mapping is required. 
The photography is used as a source of 
thematic information, to produce approximate 
maps, to update maps, and to monitor 
developments. 
The paper discusses how an operational 
system should be geared to the information 
requirements of settlement improvement 
projects, monitoring, and mapping. Cases in 
Indonesia, Tanzania, and Thailand serve as 
references. 
The character of the data derived from the 
aerial photographs is analyzed, and its 
suitability for urban planners discussed. 
Special attention is given to small format 
oblique aerial photography as a do-it-yourself 
tool for urban planners, including some 
training aspects. 
KEY WORDS: urban planning, data needs, low cost, developing countries, thematic mapping, small 
format aerial photography, map specifications, monitoring 
1 
URBAN PLANNERS, DATA NEEDS, AND MAPS 
An essential element in the information 
needs of urban planning processes is the time- 
bound character of the data. The unprecedented 
fast and enormous growth of urban areas in 
developing countries requires data collection 
and processing procedures, which are geared to 
the speed and magnitude of this growth. This 
necessitates innovative planning approaches 
and new concepts of urban surveys. 
Due to a number of factors, including 
organizational structures and procedures, lack 
of effective planning, implementation and 
control systems, budget and manpower 
constraints, etc, urban planners in developing 
countries at present face a situation in which 
they are continually running behind the facts. 
A large part of the planners' work is 
devoted to priority tasks as slum improvement 
and squatter upgrading projects, 
infrastructure planning, and site selection 
for new extensions. This work is particularly 
sensitive to the availability of up-to-date 
maps of the appropiate scale and contents. But 
the practice in a number of countries only to 
order a survey when the budget for the project 
as a whole is approved, leaves very little 
time for survey operations. Therefore, quick- 
response survey methods are required. 
Another factor is the non-availability of 
reliable and up-to-date maps and data on 
population, housing, facilities, etc, in a 
particular area. The survey, therefore, not 
only has to provide maps for planning, design 
and implementation of improvement, upgrading, 
or development of project areas,but also has 
to provide a reliable and up-to-date planning 
data base. These data, in fact, are required 
at the earliest stages of the planning 
process. 
Maps to be used for the initial planning 
do not require a high standard of planimetric 
accuracy. Only in the later planning and 
implementation stages an high accuracy may be 
needed for construction and civil engineering 
purposes. This high accuracy, however, can be 
satisfied by field measurements of only a 
limited area in a later phase. Therefore, 
rather a reliable framework for filling in 
details, than a detailed map with a very high 
overall planimetric accuracy, is initially 
required. 
Nevertheless, it is most important that 
such maps (town field sheets or approximate 
maps) are reliably showing adequate detail for 
easy orientation in the field and for 
recording location-based data. The minimum 
size and choice of objects to be 
systematically mapped (e.g. roads, 
watercourses, houses, shacks, sheds, latrines, 
water taps, trees, etc) is very critical and 
decisive for the user. The relative position 
of objects on such a map may be considered as 
more important than the absolute position: 
detached buildings have to be shown separately 
on the map, but the existence of a separating 
space is more important than the precise, 
intermediate distance. 
Such an approach will fulfil the essential 
requirements in the planning phase of a 
project and allow fast and low-cost mapping 
methods. 
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