Chapter 11 — Question 2

Describe (for a colleague) how to recognise a road on an aerial photo (make use of the

interpretation elements).

Answer

In order to recognise a road on an aerial photo, consult the following interpreta-
tion elements:

•

Tone — for asphalt roads it is expected to be dark, though for dirt-roads,
bright. Examine the image and look for those features that will look linear
(which is expected) and note the general tone.

•

Texture — we can expect a road to appear smooth. Take note of inconsis-
tencies.

•

Shape — although the width of roads change with the photo scale and
function, we should expect linear features.

•

Size — compare the relative length and width of what you consider to be
a road, with other features in the image. Does it make sense?

•

Pattern — roads have crossroads and they usually form networks. Try to
find such properties.

•

Site — Roads will tend to follow easy paths with reference to the topo-
graphy. Roads might enter tunnels and cross obstacles on bridges. Try to
find such features.

•

Association — roads function as ’easy connectors’ for people, usually from
one meaningful place to another. E.g. from a residential area to another,
or to a source of water, or to an observation point, or to a commercial area
etc. can you recognise such ’end-nodes’?

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