ISSN:0143-1161    

DOI:10.1080/014311697217909

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0143-1161    

DOI:10.1080/014311697217918

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The geometric correction of airborne scanner imagery has conventionally been performed in a non-parametric manner using ground control. Parametric geometric correction methods are less reliant on ground control and have potential for automation.Recently the possibility of correcting parametrically airborne scanner imagery has become viable because of advances in the availability and accuracy of devices that may be used to measure the exterior orientation of an airborne platform. This paper describes a study initiated by the U.K. Natural Environment Research Council (NERC) to develop and investigate a provisional parametric correction system. Flight trials were flown at an altitude of 1000 m and exterior orientation parameters measured by an inertial navigation system were used to produce parametrically corrected images. The results of this study demonstrate the feasibility of the parametric correction approach.

ISSN:0143-1161    

DOI:10.1080/014311697217927

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper outlines the rationale and design for an enhanced Airborne Remote Sensing (ARS) facility, being implemented by the Natural Environment Research Council (NERC) in the U.K., to support environmental research and monitoring. It is based on the provision of a suite of optical remote sensing instruments, available for year-round deployment, and the development of an on-board integrated data acquisition, and ground-based data processing, system. Acquisition of the remotely sensed data will be synchronized with attitude/position information from a global positioning satellite (GPS) system to enable an accurate geometric rectification to be performed. A strategy has been devised for the endto-end ground processing of this data to enable the production of standard data products and distribution in a sensor-independent data format. The facility has been fully operational from Spring 1997 and is ready to support the needs of environmental scientists and organizations requiring high quality, and immediately usable, airborne remotely sensed data products.

ISSN:0143-1161    

DOI:10.1080/014311697217936

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The spatial resolution determines the number of data and amount of information in a remotely sensed image of a given scene. The 'optimal' spatial resolution may be defined as that which maximizes the information per pixel, and this maximum is realized when the semivariance at a lag of one pixel (the average squared difference between neighbouring pixels) is maximized. For mapping, a spatial resolution should be chosen that is much finer than the 'optimal' spatial resolution as defined above. Airborne MSS images in both red and near-infrared wavelengths for three different dates and two sites were investigated to determine a spatial resolution suitable for mapping spatial variation in agricultural fields in the U.K. The spatial resolution most appropriate for mapping the spatial variation in the images was between 0.5 m and 3 m.

ISSN:0143-1161    

DOI:10.1080/014311697217945

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Gaps within woodland canopies have important ecological roles and their spatial characteristics influence regeneration processes and the diversity and distribution species. This paper investigates the potential of airborne imaging spectrometer data for characterizing the spatial properties of gaps within deciduous woodlands. Imagery obtained in summer with an Compact Airborne Spectrographic Imager (CASI) was classified to produce an accurate map of canopy gaps within several deciduous woodlands. Imagery obtained in winter proved much less informative. Principal components analysis (PCA) of separate and combined summer and winter images revealed PCs that provided information on woodland canopy structure and could be classified to give an improved delineation of canopy gaps. The spatial characteristics within the woodlands were quantified using a raster-based GIS and pattern-process relationships were used to infer the relative ecological status of the different woodlands. The ability of the aircraft to fly at short notice and the high sensitivity and high spatial and spectral resolution of the airborne spectrometer offered many advantages over broad-band satellite sensors for this application.

ISSN:0143-1161    

DOI:10.1080/014311697217954

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

This paper examines the potential to distinguish land cover types in digital images acquired at several different sensor view angles with respect to a fixed area on the Earth's surface. Images recorded by an airborne multispectral scanner over an area of arable farmland are used to generate four such multipleview-angle (MVA) datasets: each consists of data obtained at six sensor view angles in a single spectral waveband: green (0.52-0.605 mu m), red (0.63-0.69 mu m), near-infrared (0.76-0.90 mu m), and middle infrared (1.55-1.75 mu m), respectively.The data are initially presented in the form of single-band MVA false-colour composite images. These are used to illustrate the extent to which different surface materials can be distinguished visually in MVA data. The concept of MVA (cf.,multispectral) feature space is then introduced and the separability of different land cover types within it is explored. It is suggested that single-band MVA data contain two main components of statistical variance directional and spectral . Their relative contributions to the total statistical variance in single-band MVA data is assessed using linear correlation analysis and principal components analysis (PCA). It is shown that while the spectral component tends to dominate in all wavebands, particularly in the near-infrared, the directional component nevertheless provides an important means of distinguishing certain cover types. The implications of these findings are discussed in relation to the parameters used in current bidirectional reflectance distribution function (BDRF) models and the development of 'angular indices' for vegetation monitoring (cf., traditional multispectral vegetation indices).

ISSN:0143-1161    

DOI:10.1080/014311697217963

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

The results of two Daedalus Airborne Thematic Mapper surveys of phytoplankton chlorophyll in six large lakes and ten small tarns are described. The water bodies surveyed covered a range of trophic states, but were all 'Case 1' waters whose optical properties were primarily determined by the concentration of phytoplankton in suspension. The surveys were supported by in situ measurements of phytoplankton chlorophyll and radiometric measurements of the upwelling radiance at selected sites. Statistical analyses showed that radiance measurements in ATM Band 3 (520-600 nm) provided the best estimates of phytoplankton chlorophyll in the more productive waters (correlation coefficient r = 0.97). In waters where the measured concentration of chlorophyll was less than 10 mu g l -1, the most effective pigment retrieval algorithm ( r = 0.91) was that based on the ratio of the radiances in ATM Band 3 and ATM Band 2 (450- 520nm). The two algorithms were then used to estimate the average concentration of phytoplankton in each water body and to produce maps of the spatial distribution of chlorophyll in the larger lakes. Chlorophyll concentrations could be predicted with an overall accuracy of +/- 3 mu g l -1 ( r = 0.98), and spatial distribution maps produced with contour intervals of 2-10 mu g l -1.

ISSN:0143-1161    

DOI:10.1080/014311697217972

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Ground truth measurements are necessary for the validation of remotely sensed data. Rapid ship or aircraft spectral measurements of the upwelling and downwelling (ir)radiance are needed to determine the reflectance of the water column as well, as to intercalibrate with satellite sensors. Intercalibrations are hindered by the application of different instruments with varying spectal bands. It is shown that when an optical data bank (ODB) of high resolution spectra (400-720 nm) of a specific sea area is available, it is possible to reconstruct new and old reflectance spectra, accurate to within 1 per cent almost over the full spectral range, out of the reflectance measured in five bands. The ODB could contain subsurface- or airborne-collected data. It appears to be possible to use simple instruments with five specific bands to compare with satellite data, even if these differ in central wavelengths. In this way high resolution spectral data could also be stored by means of only five bands. The reconstruction technique used is based upon a multiple regression analysis (MRA) or the OBD. To validate this full reflectance spectrum reconstruction method, spectral data collected with different radiometers in different locations were successfully regenerated from five key bands (412, 492, 556, 620, and 672nm). It is proposed that airborne spectral reflectance measurements could remain limited to only five specific spectral bands.

ISSN:0143-1161    

DOI:10.1080/014311697217981

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

In this paper, we describe how high spatial resolution (10 m) multisensor remote sensing techniques can be used to study the surface roughness characteristics of large scale frontal boundaries (in this case associated with the Rhine Plume). The instrumentation employed in the research consisted of a Daedalus AADS 1268 Airborne Thematic Mapper (ATM) operated by the UK National Environment Council, the HELISCAT helicopter-borne multifrequency microwave scatterometer of the University of Hamburg, and research vessels (R.V.s) from the University of Wales and the Dutch Rijkswaterstaat. The data we present were gathered on 24 April 1991 when calm wind conditions developed within the test area. A sequence of thermal infrared images gathered by the ATM provides a record of the motion of a frontal boundary through this experimental region which is then used to identify the frontal signature in the HELISCAT data. ATM sunglint images show that the front is characterized by a zone of reduced surface roughness, some 75m in width, which is detected on the 'upstream' side of the front (as defined relative to the tidal flow direction), where surface current convergence can be expected. Radar backscatter levels at X and C bands are reduced by 10 dB in this region but with increase in radar wavelength, the signature weakens and is rarely detected at L band. On crossing the front in the downstream direction, radar backscatter levels are rapidly restored. The available evidence indicates that the reduced backscatter signature is caused by a surface slick which is formed at the frontal interface rather than by short gravity wave damping from shear in local surface currents.

ISSN:0143-1161    

DOI:10.1080/014311697218007

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor