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:: 2 Microwave data. Chairman: N. Lannelongue, Liaison: L. Krul

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: Oil drums as resolution targets for quality control of radar survey data. B. N. Koopmans

Document type:: Multivolume work

Structure type:: Chapter

Farnborough, U.K., gave an estimated spatial reso lution at 4.5 m in range and 4.0 m in azimuth. For the data correlated at the Deutsche Forschungs und Versuchsanstalt fur Luft und Raumfahrt (DFVLR), Oberpfaffenhofen, West Germany, the spatial resolu tion was in the order of 5 m or higher (Smith, op. cit.). Spatial resolution for the original optical pro cessed imagery at the Environmental Research Insti tute (ERIM), Michigan, USA, was specified as being in the order of 1.5 m in range and 2.1 m in azimuth direction (Intertech 1981), calculated on the basis of the properties of the imaging system. EXPERIMENT WITH OIL DRUMS AS SPATIAL RESOLUTION TARGETS In many radar surveys, where images are optically correlated, it has been found difficult to check the actual ground resolution of the system with respect to the resolution as specified by the contractor. The here presented experiment is based on measu ring the minimum distance between two point targets with approximately the same response strength which are still visible as two objects on the image. One option was to use a number of corner reflectors or Lunenburger lenses, placed in a grid with variable grid cell size. These reflectors are often difficult to procure, however and moreover, they are costly, especially when a survey is carried out over remote areas in developing countries. We therefore decided to test a material easily and cheaply available everywhere in the world. These consisted of oil drums, cut in half lengthwise. These half drums were welded together end-to-end. In this way, con cave upwards, they formed a perfect cylindrical reflector of a diameter of 0.7 m and a length of 2.50 m. The corrugation of the drumwalls (amplitude 3 cm) served as resonant elements and strengthened the return signal from these "drum reflectors" (fig. 1) . Fig. 1 Drum reflectors-in the test site The reflectors were oriented with their length direction either roughly parallel or slightly obli que to the flight direction. Some of them were in clined towards the look direction under different angles to check the influence of orientation on the strength of the return signal. The spacing between the drums varied between 1.5 m and 13m. The comple te configuration is sketched in figure 2. Nine "drum reflectors" were situated on line (direction 83°) roughly parallel with the flight direction (73°). They have a uniform low intensity background clut ter from a smooth grass surface. Directly south of this row of drums was a 10 m wide ploughed zone serving as a fire divide. Three more drum reflec tors were situated in the grass area between the ploughed strip and the barbed wire fence along the road (fig. 1, drums 10 - 12). On the southern side Fig. 2 Orientation of drum reflectors in the test site of the asphalt road, there is another barbed wire fence, followed by a grass strip a few metres wide and another 10m wide ploughed fire divide. Farther south, there is a rather homogeneous grass cover. The site was flown during a mission on 23 June 1981, With a synthetic aperture radar in X and C bands. Three overlapping strips cover the test area. They have been optically processed (high resolution). No digital data were obtained over this area. The northernmost strip 78 is available in X- and C-bands with depression angles of 32° towards the site. Strips 77 and 76 are available only in C-band because of a malfunction of the X-band during the flight. The depression angles are, respectively, 42° and 70°. RESULTS OF MEASUREMENTS On all four radar strips the field of drum reflec tors could be easily located as bright patches by the high radar return. The positive film has been studied under the microscope with 63x enlargement to differentiate further detail on the transparen cies. The smooth asphalt road surface appears as a dark line (light tone on the negative) as could be ex pected because of the specular reflection. On both sides of the road, light toned lines occur repre senting the barbed wire and/or the shallow depres sion along both sides of the road. This is followed by a dark toned line with a smooth surface texture, caused by the 10 m wide grass strip which separates the fence from the ploughed fire divide. The fire divide appears light in tone because of the rough- Fig. 3 Point scattering of drum reflectors on strip 77c (optically correlated)

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