Report: Data Handling in Remote SensingAuthor(s): Ray HarrisSource: Area, Vol. 11, No. 3 (1979), pp. 243-244Published by: The Royal Geographical Society (with the Institute of British Geographers)Stable URL: http://www.jstor.org/stable/20001476 .

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Measurement and statistics: the ordinal-interval controversy and geography 243

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Data handling in remote sensing

A report of a joint meeting of the IBG Quantitative Methods Study Group and the Remote Sensing Society held at Imperial College, London, 5 May 1979.

This meeting was the first of its kind between the two groups. The 40 participants directed their attention towards the different ways of handling the vast quantities of data that remote sensing satellites and aircraft have given to the scientific community. After the opening remarks by Ray Harris (Durham) emphasizing the importance of the user of remotely-sensed data, Peter Baylis (Dundee) outlined the impressive and relatively low-cost facilities that exist at the Dundee meteorological satellite receiving station. A discussion of the sensors on board the Tiros-N and Noaa satellites was followed by some very fine pictures from these satellites, and a description of the reception and processing activities at Dundee, particularly linearization and magnifica tion. The following paper by Tim Williams (Imperial) described the Imperial College interactive multichannel film processor and illustrated some of the ways in which the data received from satellites could be analysed. The processor works at television rates, so that the effects of interpretation decisions made about density slicing and decision space features can be immediately seen on the colour display monitor. Participants had an opportunity to see the film processor in action during the lunch break. The discussion that followed the two morning papers concentrated on the value of remote sensing products. Although the products are often very attractive pictures, they need to be put to good use in good quality research or operational projects.

The first paper of the afternoon session was given by Nigel Wootton (Imperial) and entitled Compressing remote sensing data. Unitary transformations, including Fourier. Karhunen-Loeve and cosine, were discussed, and a preference was expressed by Wootton for the cosine transformation because it is capable of reconstructing the original image after compression with minimum loss of information. Examples of the technique were given by compression and reconstruction of SMS-1 data for the West

African and Brazilian coasts, with little apparent loss of information. Peter Hancock (Reading) then described his research on the digital analysis of Landsat data for the study of particulate material surfaces in southern Italy. Landsat digital data had been acquired from Fucino, and after preprocessing to alleviate the influence of internal and external variations, were compared with ground truth measurements of gravel,

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244 Data handling in remote sensing

sand and silt. Particular interest was shown in the discussion after this paper in the use of regression analysis to relate ratios of Landsat wavebands to ground measure

ments, a common technique in remote sensing. Charlotte Gurney (Reading) began the final session with a paper on the use of

contextual information in remote sensing. She outlined the importance of contextual information for improving image analysis accuracy, and gave two examples of the value of context information: first, in the extraction of true woodland in the Reading area by analysis of Landsat data, using distance, size and containment criteria; and secondly, in the extraction of linear from non-linear features by using size and orienta tion criteria. The use of contextual information in conjunction with density and texture information remains a largely unexplored, and potentially rewarding, field of image processing. A tantalizingly brief view of future remote sensing was given by

David Stanley (Logica Ltd.) in a paper entitled Satellite image products for the next decade. Landsat has a very useful multispectral scanner, but it is only a first generation instrument and will be superseded by more sophisticated sensors in the near future.

One important feature of the new sensors will be their ability to perform some elemen tary processing of remotely-sensed data by an on-board classifier, and transmit the analysed data to ground stations in a partially processed form. The likely improvements in platforms, orbits, payloads and forms of pre-processing were discussed, and artist impressions were used to illustrate the exotic candidates for future remote sensing orbiting platforms. One of the most intriguing of these was a texturometer, which measures 50 m in height, carries 360 mirrors, and, its designers claim, can measure the surface texture of the earth at the millimetre scale. The discussion that concluded the session centred on the value of remote sensing to the environmental scientist. The types of products provided by remote sensing are often complementary to existing data sources, and the value of remote sensing should be seen in this light. One of the great benefits of remote sensing is the monitoring of environmental change, and the continuing provision of data for geographical information systems is of great value, particularly in the developed countries.

Handling the data mountains presented by remote sensing creates many problems, but is is also a rewarding activity in that it can convert remotely-sensed radiance data into a useful form for mapping and monitoring operations.

Ray Harris University of Durham

Sussex Working Papers Sussex Working Papers in Urban and Regional Studies. The most recent numbers in this series are as follows:

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