摘要:

Highly effective small-scale remote sensing can be carried out using a remotely piloted aircraft as a platform for various instruments. The operation of such a platform is described and details of two sensors (a photographic camera and a multiband radiometer)are given. Some preliminary results are presented and future developments are discussed.

ISSN:0143-1161    

DOI:10.1080/01431168608948957

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A general classification of radiometric correction methodologies yields new insights into related procedures as they are implemented typically on image analysis systems. Incorrect results can be obtained from the inappropriate application of different types of corrections related to physical phenomena which give rise to radiometric distortions in a scene. The major types of radiometric correction are reviewed as they apply to digital images acquired by satellite sensors in the visible and infrared portions of the spectrum.

ISSN:0143-1161    

DOI:10.1080/01431168608948958

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Eleven environmental variables, elevation, slope angle, slope aspect, surface roughness, soil type, geology, percentage of vegetation, percentage of trees, percentage of shrubs, percentage of herbs, and percentage of bare ground, are evaluated as to their impact on LANDSAT thematic mapper (TM) spectral signatures. Multiple regression models indicate that a combination of percentage of trees and shrubs have the most significant impact on TM spectral response, and, in fact, mask the effects of other tested environmental variables. Regression models are also developed for major soil types which significantly predict the amount of trees and shrubs present on a site.

ISSN:0143-1161    

DOI:10.1080/01431168608948959

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Pre-harvest production of maize in Kenya was estimated using radiometry and aerial photography. Twenty-five strata covering 61 000 km2contained 900 000 ha of maize. The ratio of near-infrared (NIR) to red reflected from maize fields was measured with airborne radiometers over 100 fields. The actual yields were measured immediately prior to harvesting. A regression (R2= 0·77) predicting yield from NIR/red was obtained. A systematic radiometric survey was conducted and the regression was used to estimate the pre-harvest yield in all maize growing strata. The average nation-wide yield was 372 t/km2, giving a total production of 3360 kt.

ISSN:0143-1161    

DOI:10.1080/01431168608948960

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A method of estimating the quantity of biomass in the ground layer of semi-arid rangeland is described and applied to a region of 700 km2in Botswana. Vertical true colour diapositives, each covering approximately 60 × 90 m, were taken at 1 km intervals from a light aircraft flying at about 120 m above the ground along transects 1·6 km apart. The results of four seasonal surveys are presented. The ground layer cover, as a percentage, was estimated on each diapositive. It ranged mainly from 10 to 60 percent. A set of sampling plots on which the cover and biomass were measured on the ground provided standards for the air photograph estimates and a calibration equation of exponential form from which to convert estimates of cover to those of biomass. The values obtained were analysed spatially. Sample semi-variograms were computed and modelled as anisotropic power functions to lags of 10 km by least squares approximation, and validated by kriging. The grass cover and biomass were mapped from the sample data by first interpolating a figure field of cover on a fine mesh grid by kriging, and then contouring the figure field. The maps were converted to ones of biomass using the exponential calibration equation. A strong regional pattern emerged that remained fairly constant at different seasons and that matched the pattern in the underlying geology. Four fairly distinct sub-regions were delineated, and the average cover and total biomass were estimated, again by kriging, for each seasonal survey. Biomass in the sub-regions ranged from 185 to 1700 kg/ha.

ISSN:0143-1161    

DOI:10.1080/01431168608948961

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The purpose of this study was to compare some classification methods on a typical Hungarian lowland agricultural area. For a multicrop test area of approximately 20000 ha several one-date and multi-date LANDSAT MSS data sets were classified using supervised and unsupervised methods. The best results were obtained by clustering two-band Kauth-Thomas transforms for each date, using Swain-Fu inter-cluster distance. In general, clustering Kauth-Thomas bands always showed slightly better accuracy than the ones for the MSS 5 and MSS 7 data sets. The accuracies achieved by polygon-vector classification were lower (3–6 percent) than those of multidate clustering. An effort was made to explain the results in terms of spectral separability of agricultural cover classes. The ratio of the average separability of an individual class and the total data set is proposed to measure classification accuracy on areas similar to the Kisköre test site.

ISSN:0143-1161    

DOI:10.1080/01431168608948962

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

An experimental analysis has been conducted on the performance of the new LANDSAT-5 Thematic Mapper (TM) data for detailed land-cover classification using a maximum-likelihood method. Data used is the TM test data of the Tokyo metropolitan area (path-107, row-035) of 4 November, 1984. Map-precision geometric correction is performed and TM data are resampled to 30  m pixel spacing. The experiment is designed to determine how well TM categories land-cover types in comparison with the Detailed Numerical Information digitally formatted data (Geographical Survey Institute of Japan, 10  m spatial accuracy), together with ground truth data in a representative test area. Classification accuracy for aggregated 12 categories within the test area is about 47 per cent with the application of the explicit filtering technique utilizing 3×3 neighbourhood operations. This increases to 70 per cent using a majority logic filter with a larger 5×5 neighbourhood function. Associated with the classification accuracy, effects of the mixed pixels are also investigated. The results show that the improved characteristics of TM aided the overall classification accuracy.

ISSN:0143-1161    

DOI:10.1080/01431168608948963

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A LANDSAT-based rangelands monitoring system has been designed for semi-arid chenopod shrublands in southern Australia. Simultaneous ground and LANDSAT measurements were used to test multivariate calibration methods for estimating vegetation cover. Of three methods compared, the Lwin-Maritz and inverse estimators outperformed the classical approach. Data were analysed by rangeland type and as a combined set. Calibration curves, with errors of estimation, are presented for five major rangeland types.

ISSN:0143-1161    

DOI:10.1080/01431168608948964

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Les valeurs d' émissivité de sols nus obtenues dans la bande 8-14 μn par la formule de Kirchhoff, a partir de mesures de la réflectivité bidirectionnelle, sont comparées aux émissivités mesurées par la méthode de la ‘boite’. Les écarts observés sont faibles, inférieurs aux incertitudes expérimentales, ce qui confirme la validité du modéle de dilTusion sur lequel s'appuie le calcul de la reflectivité. L'utilisalion de la méthode active en télédetection fait inlervenir, dans la relation entre émissivité et rétrodiffusion, un facteur de forme caractéristique du milieu. Quelques exemples mettent en évidence I'importance de ce facteur dont I'omission peut, selon le cas, entraîner une erreur sur ϵ de plus de 2 pour cent. Le comportement angulaire et spectral du facteur de forme, tel qu'il se degage de cette premiére etude, implique, pour la mise en oeuvre de la méthode, des investigations plus poussées sur les mécanismes de la réflexion diffuse et la réponse spectrale des milieux à I' état naturel.

ISSN:0143-1161    

DOI:10.1080/01431168608948965

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A comparison is made between lineament analyses made from side-looking radar (SLAR)imagery, LANDSAT and aerial photographs from an area on the Lamurde anticline (Benue Valley) and from an area of ring dyke complexes (Jos Plateau), Nigeria. Fault lineaments are, in general, well expressed on side-looking airborne radar with the exception of those lineaments orientated parallel or subparallel to the radar look direction. Look direction and radar incidence angle influence lineament detectability. Specifically the lineaments oriented perpendicular to the Sun azimuth direction on the LANDSAT image were over-represented. LANDSAT, SLAR and aerial photographs can be used in a complementary way; the first two for reconnaisance-type surveys and lineament analysis, the third for detailed surveying.

ISSN:0143-1161    

DOI:10.1080/01431168608948966

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor