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Quantitative microwave backscatter measurements from the ocean surface using digital marine radar images

Quantitative microwave backscatter measurements from the ocean surface using digital marine radar images
Quantitative microwave backscatter measurements from the ocean surface using digital marine radar images
The capabilities for quantitative measurements of the ocean backscatter at low grazing angles of a conventional low-budget X-band marine radar associated with a commercial digital capture board are investigated. Details are given of the external and internal calibration methods designed to determine the system’s transfer function. This work reveals that the accurate system transfer function can be determined only by calibrating the composite system in one single step. Results of an absolute calibration attempt using buoy-based corner reflectors in very calm weather conditions are presented. The dynamic range is deduced and found to span over a 50-dB range well suited to describe the ocean backscatter coefficient values expected at low grazing angles. The analysis of the overall error budget and system stability provides a theoretical estimate of the system’s relative radiometric resolution. The marine radar system is found to produce backscatter coefficient images with a relative error typically of the order of 1 dB. When averaging over several antenna rotations, the error reduces further down to 0.6 dB, where it compares favorably with the performance of traditional research radar systems. It is concluded that despite the inexpensive nature of these instruments, marine radar systems represent a tool that is effective in routinely providing reliable quantitative measurements of the sea surface roughness, which may serve to complement the synoptic views offered commonly by satellite or airborne radars.
BACKSCATTER, RADAR IMAGERY, REMOTE SENSING, MICROWAVES
0739-0572
665-678
Gommenginger, C.P.
f0db32be-34bb-44da-944b-c6b206ca4143
Ward, N.P.
c41998de-355f-4c9b-b18e-55cf36047cf3
Fisher, G.J.
5583221a-f6e9-42e1-964a-c51facc6219f
Robinson, I.S.
548399f7-f9eb-41ea-a28d-a248d3011edc
Boxall, S.R.
ee92cf98-339f-4b43-ac1d-b4a4c983ffe2
Gommenginger, C.P.
f0db32be-34bb-44da-944b-c6b206ca4143
Ward, N.P.
c41998de-355f-4c9b-b18e-55cf36047cf3
Fisher, G.J.
5583221a-f6e9-42e1-964a-c51facc6219f
Robinson, I.S.
548399f7-f9eb-41ea-a28d-a248d3011edc
Boxall, S.R.
ee92cf98-339f-4b43-ac1d-b4a4c983ffe2

Gommenginger, C.P., Ward, N.P., Fisher, G.J., Robinson, I.S. and Boxall, S.R. (2000) Quantitative microwave backscatter measurements from the ocean surface using digital marine radar images. Journal of Atmospheric and Oceanic Technology, 17 (5), 665-678. (doi:10.1175/1520-0426(2000)017<0665:QMBMFT>2.0.CO;2).

Record type: Article

Abstract

The capabilities for quantitative measurements of the ocean backscatter at low grazing angles of a conventional low-budget X-band marine radar associated with a commercial digital capture board are investigated. Details are given of the external and internal calibration methods designed to determine the system’s transfer function. This work reveals that the accurate system transfer function can be determined only by calibrating the composite system in one single step. Results of an absolute calibration attempt using buoy-based corner reflectors in very calm weather conditions are presented. The dynamic range is deduced and found to span over a 50-dB range well suited to describe the ocean backscatter coefficient values expected at low grazing angles. The analysis of the overall error budget and system stability provides a theoretical estimate of the system’s relative radiometric resolution. The marine radar system is found to produce backscatter coefficient images with a relative error typically of the order of 1 dB. When averaging over several antenna rotations, the error reduces further down to 0.6 dB, where it compares favorably with the performance of traditional research radar systems. It is concluded that despite the inexpensive nature of these instruments, marine radar systems represent a tool that is effective in routinely providing reliable quantitative measurements of the sea surface roughness, which may serve to complement the synoptic views offered commonly by satellite or airborne radars.

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More information

Published date: 2000
Keywords: BACKSCATTER, RADAR IMAGERY, REMOTE SENSING, MICROWAVES

Identifiers

Local EPrints ID: 8917
URI: https://eprints.soton.ac.uk/id/eprint/8917
ISSN: 0739-0572
PURE UUID: 7c379838-3204-425d-a935-a199d1f302e1

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Date deposited: 10 Sep 2004
Last modified: 17 Jul 2017 17:12

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Contributors

Author: C.P. Gommenginger
Author: N.P. Ward
Author: G.J. Fisher
Author: I.S. Robinson
Author: S.R. Boxall

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