The philosophical underpinnings of remote sensing

The philosophy behind remote sensing can perhaps be divided up into three sections, first, what the technology is; second, why the technology has been developed, and how it has developed; and third, what the technology is used for, and why it is of benefit.

Firstly, what is remote sensing? A standard definition is provided by Lillesand and Kiefer (1994), who describe remote sensing as:

"the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation" (p.1).

Using our eyes to read or look at any object is also a form of remote sensing. However, remote sensing includes not only what is visual, but also what can’t be seen with the eyes, including sound and heat (although these can also be turned into a visual representation as well).

Secondly, why has remote sensing been developed? Remote sensing has a very long history dating back to the end of the 19th century when cameras were first made airborne using balloons and kites. The advent of aircraft further enhanced the opportunities to take photographs from the air, and perhaps World War 1 saw the first major use of remote sensing as a method of data and information acquisition. The history of remote sensing appears to show a logical route as to why remote sensing was developed, and continues to be developed. Initially, still photography would have provided (and still does) a fascinating and exciting way of capturing moments in time, a record of something that happened that looked more realistic than a drawing or painting, and that could be captured much quicker than by drawing or painting. With an insight to perspective, and a possible interest in landscape photography, a photographer would soon realise that a different and perhaps more revealing view of a particular landscape (whether built or natural) could be gained by taking a photograph from a vantage point, such as an incline or building. It is, therefore, not surprising that airborne photography was soon embraced, initially perhaps through simple experimentation, but later because it was realised that the airborne perspective gave a completely different view to that which was available from the ground. Arguably, this different view that remote sensing affords of the Earth was historically, and is now the main driving force behind the continued development of remote sensing.

Today, remote sensing is carried out using airborne and spaceborne methods using satellite technology. Furthermore, remote sensing not only uses film photography, but also digital camera, scanner and video, as well as radar and thermal sensors. Whereas in the past remote sensing was limited to what could be seen in the visual part of the electromagnetic spectrum, the parts of the spectrum which can not be seen with the naked human eye can now be utilised through special filters, photographic films and other types of sensor. The advantage of a different view of the Earth has, therefore, been further enhanced by new information about the environment available outwith the visible spectrum.

Remote sensing was then initially developed through experimentation. However, the unique view of the Earth which it offered was soon applied to practical and real applications, the most notable of which is probably aerial reconnaissance during the First World War. Aerial photography allowed the positions of the opposing armies to be monitored over wide areas, relatively quickly, and more safely than a ground based survey. Aerial photographs would also have allowed rapid and relatively accurate updating of military maps and strategic positions. Today, the benefits of remote sensing are heavily utilised in environmental management which frequently has a requirement for rapid, accurate and up-to-date data collection. Remote sensing has many advantages over ground-based survey in that large tracts of land can be surveyed at any one time, and areas of land (or sea) that are otherwise inaccessible can be monitored. The advent of satellite technology, and multispectral sensors has further enhanced this capability, with the ability to capture images of very large areas of land in one pass, and by collecting data about an environment that would normally not be visible to the human eye.

Remote sensing has come to be a very important method of data collection about the environment, and this is largely due to the unique view that it provides us of the Earth. However, remote sensing has not yet totally replaced ground-based survey methods and this is largely because some limitations with the technology still exist. These include potential limitations with spatial, spectral and temporal resolutions of the various sensors, problems with all weather capability (not all sensors can ‘see’ through cloud), costs of data collection and data purchase, and problems with data analysis and interpretation. While remote sensing is a useful technique, it can still only supplement ground surveys. However, the insight that it provides into the environment, its features and processes is extremely valuable indeed.

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