摘要:

Simultaneous acquisition of Landsat TM imagery and sea truth data from sample sites in Himmerfjärden bay on the Swedish east coast was conducted on 10 May 1988, and 7 May 1990. The data were used to develop and verify regression models for the estimation of surface chlorophyll-a concentrations. The case 2 waters studied partly hold suspended sediment concentrations known to complicate the mapping of chlorophyll-a. The disturbing spectral influence from suspended sediment was reduced by using a process based on an existing Landsat TM sediment retrieval algorithm and a priori knowledge about water depths, bottom sediments and river outlets. The results suggest that a ratio of TM bands TMl/(log TM3+1) should be used in waters influenced by terrigenous influx and the earlier suggested ratio of TM bands 1/2 only in ocean waters. The discrimination power indicated a capability to quantify chlorophyll in connection with algae blooms.

ISSN:0143-1161    

DOI:10.1080/01431169208904240

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In preliminary trials of an X-band side-looking airborne radar (SLAR), surface schools of fish were seen as distinct targets. Radar backscatter from the fish schools was influenced by the behaviour of the fish and the angle of the radar beam relative to the prevailing wind and wave conditions. Detection of targets was partly masked by radar backscattering from modulation of the Bragg-scale waves by oceanic phenomena, radiometric variations due to aircraft motion, and ‘bursts’ from breaking waves. Fish spotting was carried out by three methods: (i) visually, (ii) with the grey-scale image on a monitor supplied with the radar, and (iii) with a real-time display produced by a microcomputer interfaced lo the SLAR processor unit. Target signals were enhanced on the microcomputer in real-time using a difference filter, and colour-coding was used to differentiate the strength of targets. This procedure revealed several weak backscattering targets not visible in the unenhanced black-and-white display. The 'boiling’ surface disturbances created by frenzied feeding schools of jack mackerel were detected visually within a few kilometres of the aircraft and by the radar out to a range of 30km. Non-feeding schools of southern bluefin tuna created a surface rippling, similar to that caused by light winds, which could not be detected without image enhancement.

ISSN:0143-1161    

DOI:10.1080/01431169208904241

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

On 19 January 1988, and experiment was carried out to establish the positional relation between corresponding features in radar imagery and bottom topography. The radar measurements were done with the Dutch Digital SLAR, an X-band HH polarized SLAR system. The experiment look place in an area 30 km off the Dutch coast where the bottom topography is dominated by sand waves with a height between 2 and 6 m and a crest-to-crest distance of typically 500 m at a depth of 22 m. Ground data were recorded from two ships near the centre of the test area and from the Measuring Platform Noordwijk, 20 km from the test area. By comparing the radar images showing sand waves with digitized maps of depth and bottom slope it is concluded that the extremes in the radar backscatter are located right above regions with maximum bottom slope, within a positional accuracy of 30 m. This is in excellent agreement with predictions by simple relaxation models of the imaging mechanism.

ISSN:0143-1161    

DOI:10.1080/01431169208904242

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431169208904243

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/01431169208904244

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor