19
Role of Photo-Interpretation
If urban data bases become operational, they may supply certain data
new derived from photographs, such as small area population forecasts, changes
in built-up areas (Gould 1975), land use information etc. To assess the future
potential of photo-interpretation in such a situation, it is necessary to dis-
tinguish between the different functions photography might then have:
(a) direct data source — information for the data base is collected
directly from the photographs;
(b) checksonconsis ^ — photography is used to check quality, com-
tency and com- pleteness and consistency of other sources;
pleteness
(c) additional infor- — information is derived from photographs that
mation is not available from the data base, for example
because it is not “parcel based" (some environ-
mental variables) or because it is outside the
urban area (data for extension schemes).
As a direct data source, photography constitutes one of the sources available.
In general, input will enter the system basically from four sources, which only
partially compete with each other:
administrative bookkeeping (population, education etc)
surveys — systematic or ad hoc (agricultural land use, economic data etc)
census — national or local census statistics
remote sensing (land use, built-up area).
The better the quality of the administrative system (as to both accuracy and
extensiveness), the less the need for other systems. Thus Denmark will abolish
its national census when the national property register is operational (Black
1975).
Remote sensing data will only be competitive for information that is
not (or is incompletely) known by administrative procedures. It has to be
realised that some existing administrative procedures may in the future become
too expensive or inacceptable to the general public (privacy problem).
Remote sensing might then be a feasible alternative.
The ITC is actually carrying out a joint research and implementation
programme, together with the municipality of Enschede (where the institute
