Remote sensing for resources development and environmental management: Remote sensing for resources development and environmental management

Damen, M. C. J.

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Multivolume work

Persistent identifier:: 856342815

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856342815

Language:: English

Additional Notes:: Volume 1-3 erschienen von 1986-1988

Editor:: Damen, M. C. J.

Document type:: Multivolume work

Volume

Persistent identifier:: 856343064

Title:: Remote sensing for resources development and environmental management

Sub title:: proceedings of the 7th international Symposium, Enschede, 25 - 29 August 1986

Scope:: XV, 547 Seiten

Year of publication:: 1986

Place of publication:: Rotterdam; Boston

Publisher of the original:: A. A. Balkema

Identifier (digital):: 856343064

Illustration:: Illustrationen, Diagramme

Signature of the source:: ZS 312(26,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: Damen, M. C. J.

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: 1 Visible and infrared data. Chairman: F. Quiel, Liaison: N J. Mulder

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Detection of subpixel woody features in simulated SPOT imagery. Patricia G. Foschi

Document type:: Multivolume work

Structure type:: Chapter

Symposium on Remote Sensing for Resources Development and Environmental Management / Enschede / August 1986 Detection of subpixel woody features in simulated SPOT imagery Patricia G.Foschi School of Geography, Oxford, UK ABSTRACT: A method for detecting small woody features in digital imagery was developed. Woody features, ranging in size from hedgerows to strips or patches several trees wide, were tested. The classification method correct ly detected all subpixel woody features larger than hedgerows and identified about 20 percent of the hedges. 1 INTRODUCTION In Britain, changes in farming practices since the 1940s have resulted in tree, pond, and hedgerow remov als, larger field sizes, and less frequent crop rota tions (Body 1982, Sturrock & Cathie 1980). Although tree and hedge removals are small land cover changes, they are significant landscape and habitat changes. These changes which decrease habitat diversity affect animal and bird populations. Studies have shown that birds and mammals utilize diverse landscape elements (Pollard & Relton 1970, Wegner & Merriam 1979) and that their distributions are related to the shape, size, and spatial arrangement of these landscape ele ments (Forman & Godron 1981, Helliwell 1976). Monitoring and quantifying agricultural change is necessary for effective land use planning and wildlife habitat management. Computer-assisted methods using remotely sensed data could provide timely monitoring of changes in woody vegetation which affect scenic beauty and wildlife. Since linear woody features are often subpixel tar gets or features smaller than the pixel size of the image, pixels containing these features are usually mixed pixels or pixels containing two or more land cover classes. Because the spectral values of mixed pixels containing woody features frequently do not correspond to the spectral values of woody vegetation, conventional multispectral classification techniques which operate on single pixels are problematic and re peatedly result in mixed pixels being placed in con stituent or extraneous classes. A method for detecting subpixel woody features in digital imagery was devel oped. Unlike conventional classification techniques, this method incorporates information about adjacent classes and mixture phenomena at the individual pixel level. 2 2 DATA AND STUDY SITE As the method developed is concerned with detecting small landscape features, it was appropriate to use digital imagery of a high spatial resolution. Since SPOT data was not available when the project was be gin, simulated SPOT data was acquired for the project. In 1984, the National Remote Sensing Centre (NRSC) in Famborough, England organized a campaign to in vestigate the usefulness of SPOT imagery prior to its availability. Simulated SPOT data was collected over a wide variety of sites in the United Kingdom in order to test a number of applications (NRSC 1985)■ This im agery was also sold to the public and, subsequently, a scene was acquired for this project. Of the 39 test sites imaged, the Winchester data flown on 6 July 1984 was selected because it is representative of agricul tural lands in lowland Britain and because it contains numerous linear woody features. A subscene of the Winchester image was then selected for use in developing and testing algorithms. This subscene, approximately 17 sq km on the ground, is lo cated southeast of the city of Winchester in a gently rolling area of mixed farmland and woodland. Panchromatic photography, commissioned by the Plan ning Department of the Hampshire County Council, was used to locate and map woody vegetation within the subscene. This photography was flown by Meridian Air- maps Limited on the evening of 28 July 1984 at 1:10000 scale. Four categories of woody vegetation were mapped: hedgerows, single trees, single rows of trees, and denser woody features. Specific species were not identified. The airphoto interpretation was checked by surveying parts of the study site on the ground. 2.1 Comparison of real and simulated SPOT imagery The simulated imagery was flown by Hunting Geology and Geophysics Limited with a Daedalus DS-1268 multispec tral scanner. Daedalus channels 3 through 7 were used singly or in combination to simulate the SPOT channels (Hunting Geology and Geophysics Ltd. 1984). The wave lengths of these simulations do not exactly match those of the real SPOT bands. The effect of these dif ferences is not known. Table 1. Comparison of SPOT and simulated SPOT chan nels . Channel SPOT wavelengths in microns Daedalus channels Simulated SPOT wavelengths in microns SI O.5O - O.59 3 O.52 - O.60 S2 O.6I5 - 0.68 4+5 O.605 - O.69 S3 0.79 - 0.89 7 O.76 - O.9O p O.5I - 0.73 3+4+5+6 O.52 - O.75 The spatial resolutions of real and simulated SPOT data are the same: 20m in the three multispectral bands and 10m in the panchromatic band at nadir view ing. Since the simulated SPOT imagery was flown by high- altitude aircraft, it is less map-accurate than sat ellite imagery. Distortions in aircraft imagery are caused by changes in aircraft altitude and angular orientation during scanning. Since spatial fidelity is not important in this project and since techniques for geometric correction inevitably involve interpolation which further "mixes" the information in the pixels, there has been no attempt to geometrically correct the imagery. Another difference between real and simulated SPOT data is the sun angle. The simulated imagery was col lected at about mid-day and, consequently, shadows are

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