How can we conceive an aerial photograph and/or a remote sensing image?

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How can we conceive an aerial photograph and/or a remote sensing image?

A. As a set of fundamental photorecognition elements

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B. As a registration of sets of :
points (e.g. trees),
lines (e.g. boundaries, networks, rivers and streets at small scales),
area features (e.g. parcels, highways),
spatial features (e.g. landscapes),
defined in terms of the way they reflect or emit radiation in different time (years, seasons, hours) and different wavelengths.
By combining the photorecognition elements with the recognition of specific point, line, polygon and spatial features –as shown in the following table- we can facilitate interpretation and information extraction.

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The photointerpreter’s “function” in applying remote sensing/photointerpretation methodologies generally follows the procedure below:

The photointerpreter’s mental stimulation, enabling him/her to carry out the photointerpretation process, results from:

a. his reaction/response to the image/a pair of remotely sensed images basic data:

Tone/Shade of colour.

Shape/Form.

Size.

Pattern.

Texture.

Shadow.

Sensation/Measurement of the 3rd dimension.

Topographic location.

Relation to the local environment (context).

b. the progressive exploration of the remotely sensed images, starting from the simpler and easily understood image characteristics (tone/shades of colour), to the more complex ones (relation to the local environment), in order to acquire the information available.

It is obvious that the remotely sensed images of an area/region could be:

In analogue or digital form.

At the same/different scale.

Of the same/different resolution.

A simple image or a pair of images.

Of the same/different date.

Of the same/different season of the year.

Of the same/different time of acquisition.

Sensitive to the same/different areas of the electromagnetic spectrum.

Of the same/different positioning of the flight axis.

Taken from the same/different remote sensing sensors/systems.

Taken with the same/different/specific geometry conditions (for example: aerial photographs with inclined/perpendicular axis, radar images with horizontal/ perpendicular polarization etc.).

The analysis of these remotely sensed images can be carried out either using analogue photointerpretation, or digital methods and techniques, or by a combination of the methods mentioned above.
Although the basic image data are a point of reference during the analogue/digital process of the revelation/“identity check” of objects/phenomena and in working out of the relevant problems, it is obvious that the exploitation of these data depends on the possibilities and the restrictions of the methods and practices selected and on the information/infrastructure available.

Reference:.Rokos, D. “Photointerpretation and Remote Sensing”, NTUA, 1979

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National Technical University of Athens
Dept. of Rural & Surveying Engineering
Laboratory of Remote Sensing