ISSN:0143-1161    

DOI:10.1080/01431169508954641

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A radiative transfer approach to the problem of atmospheric correction of satellite images in the solar spectral range is presented which includes all multiple scattering processes without any approximation. The numerical solution is accepted as satisfying, if the numerical accuracy is better than I per cent. This means that the accuracy of the atmospheric correction depends almost exclusively on the quality of the auxiliary data on the atmospheric state and the surface reflection indicatrix. Byextensivemodel calculations these parameter driven error bounds have been quantified. Thus the calculation results in a corrected albedo image with specified error bounds. This seems to be the first algorithm available for atmospheric correction of real imagery data which relies on a numerical exact treatment of multiple scattering. The program EXACT (EXact Atmospheric Correction Technique) has so far been used with Landsat Thematic Mapper (TM), NOAA AVHRR (National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer) and also with airborne Daedalus ATM images. The algorithm has been validated by comparison of satellite data to ground measurements and between different sensors. Errors of the derived albedos were found to remain below 0·01 for visible and near-infrared sensor channels of this set of radiometers.

ISSN:0143-1161    

DOI:10.1080/01431169508954642

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Laboratory reflectance spectra of 91 soil samples from Israel were convolved into the six Thematic Mapper (TM) band passes allocated within the YIS-NJR-SWIR spectral region (0·4–2·5 jlm). The TM spectra were used as raw data against which to run the NIRA-YNIRA (near-infrared analysis and visible and near-infrared analysis, respectively) procedure using a method called Thematic Mapper Analysis (TMA). Several soil properties and constituents were examined for possible prediction from the TM spectra, but only four were found to be significantly predictable: carbonates (CaCO3), specific surface area (SSA), total silica (SiO2) and loss-on-ignition residual (LOI). The prediction of each property was based on the total apparent reflectance value (albedo) rather than specificabsorption. The intercorrelation between the properties (particularly with CaCO3) is considered the major pathway in which the spectral-based prediction took place. Prediction performance of TMA is still low relative to the results obtained using a similar population and an analysis routine for highest spectral resolution data. Under the extremely difficult conditions of the TMA run (low spectral resolution and complex soil matrix) the prediction performance is likely to be good and is very promising for the remote sensing applications of soils. Further study with real TM data and field measurements is strongly recommended.

ISSN:0143-1161    

DOI:10.1080/01431169508954643

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Geophysical and Environmental Research (GER) 63 channel scanner data were used to map the surface mineralogy of Makhtesh Ramon, Negev, Israel. The data werecorrected to reflectance using the Internal Average Relative Reflectance (IARR) method and analysed using colour-composites, the Spectral Angle Mapper (SAM), and linear spectral unmixing (UNM). Results demonstrate that imaging spectrometer data can be used to produce detailed mineralogical maps in arid terrains even when no calibration measurements are made during the flights and no ground measurements are available. The mineralogical maps produced using the GER data compare favourably to the known surface mineralogy, however, they provide greater detail regarding composition and mineral abundance than the existing geological maps.

ISSN:0143-1161    

DOI:10.1080/01431169508954644

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

An iterative, physically model based inversion algorithm has been used to estimate root mean square (r.m.s.) surface roughness height from radar data. collected over vegetated areas. The model is based on a discrete scatterer random media technique, and employs the distorted Born approximation to model the backscatter coefficients for a given scene. In the model, the Fresnel reflectivity (a measure of soil moisture) and surface roughness appear together in the vegetation-ground interaction term. An approach is followed that utilizes differences in their frequency response to separate the two. Sensitivity analysis shows that the change in surface reflectivity owing to the change in frequency from the L- to C-band is dominated by surface r.rn.s. height. The Fresnel reflectivity stays almost constant over this frequency interval. The inversion algorithm based on these sensitivity differences is applied to the backscatter model data from a plant canopy of soybean. Calculations show that the technique gives accurate results from a model backscatter data set that is corrupted with random noise. The inversion algorithm is also applied to Synthetic Aperture Radar (SAR) data collected over corn fields during the MACHYDRO'90 experiment in Pennsylvania, USA. There is an excellent agreement between the measured and the estimated r.m.s, surface height.

ISSN:0143-1161    

DOI:10.1080/01431169508954645

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The Normalized DilTerence Vegetation Index (NDVI) derived from NOAA's Advanced Very High Resolution Radiometer (AVHRR) has been widely used in monitoring continental and global vegetation distribution and dynamics, drought severity and location, and environmental deterioration. Since 1982, NOAA has produced the Weekly Global Vegetation Index (GVI) product from AVHRR. The analyses of the GVI product have revealed many problems due to the simplified radiometric correction involved in the processing. Those limitations have inspired several elTorts to reprocess the NOAA GVI data sets to produce an improved representation of global NDVI patterns. In this paper, the quality of three Global NDVI products resulting from very simple to rather sophisticated reprocessing was examined by using a global approach. In general, the quality of data improves with increasing sophistication of radiometric correction. However, this study reveals some significant errors common in all three products assessed. The problems include a systematic annual increase in values computed from a single satellite and jumps between consecutive satellites. These errors are large enough to alTect results of the long term time-series analyses. This pattern suggests an additional radiometric distortion in NOAA/ AVHRR data. It is found that the values computed from data of the first year after satellite launch are roughly the same statistically for NOAA satellites. Thus, the discontinuity ofNDVls between satellites appears to be mainly caused by the systematic drift. Therefore, data collected in the first year of satellite launch might be considered as a baseline for correcting the systematic errors. By comparing NDVI from the first year of satellites in space, it is also found that NDVI increases at higher latitude and decreases or keeps constant at lower latitude. This change of NDVI with time might signal the change of global climate.

ISSN:0143-1161    

DOI:10.1080/01431169508954646

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Analysis of diversity and evenness metrics using land cover data are becoming formalized in landscape ecology. Diversity and evenness metrics are dependent on the pixel size (scale) over which the data are collected. Aerial photography was interpreted for land cover and converted into four raster data sets with 4, 12, 28, and 80m pixel sizes, representing pixel sizes up to that available on Landsat-MSS. Analysis of covariance was used to determine the effect of changing pixel size on landscape metrics. The results indicate that landscape metrics should not be dramatically affected by the change in pixel size up to 80m, provided that identical land cover classifications could be generated by sensors with different spatial resolving powers (e.g. Landsat-TM and MSS).

ISSN:0143-1161    

DOI:10.1080/01431169508954647

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A multiwavelength Laser Remote Sensing (LJDAR) system (EOLE Project) for daytime and night-time vertical profile measurements of ozone and aerosols in the troposphere and the lower stratosphere (0·5–15 km) is proposed. The EOLE lidar system uses state-of-the-art solid state laser and electronic technologies and is designed to be rugged, modular and simple to operate. Further, in this paper, we present the scientific objectives of the EOLE Project and briefly describe the experimenlal set-up of the EOLE lidar system. The expected measurement accuracy, in both ozone and suspended particles (aerosols) observations, is briefly discussed, as well as the calibration procedures of the proposed lidar system.

ISSN:0143-1161    

DOI:10.1080/01431169508954648

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polarimetric AIRSAR data of 13 July 1990 acquired over Mahantango watershed area were processed for the identification of cornfields and forested areas. Polarization Phase Difference (PPD) values were computed for the cornfields atP-,L- andC- bands and studied as a function of frequency. The results compare well with the model calculations at 24° incidence angle, whereas the locations of cornfields were computed to be at 35° incidence angle. The discrepancy is attributed to a lack of accurate ground truth and the undulating topography of the cornfields. Another study reported here deals with the usefulness of the Polarization Index (PI) for the study of vegetation. PI was found to be dependent on the frequency for the cornfields, whereas for forest trees no such dependence was noticed.PIHH,HVis a more useful parameter thanPIHH,HVeven for the study of cornfields.

ISSN:0143-1161    

DOI:10.1080/01431169508954649

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The SeaWiFS potential for identifying the marine cyanobacterium Trichodesmium, at low concentration in oligotrophic case I waters, has been investigated by numerical simulations using a three-component model of sea colour. The results obtained indicate that simple algorithms, which operate on data recorded by SeaWiFS bands 2, 3. and 5, should have the capability to discriminate pixels containingTrichodesmiumat concentrations as low as 0·1–0·3 mgm-3chlorophyll a, as well as to yield an estimate of the concentration. The validity range of the procedure has been explored by a sensitivity analysis, assuming realistic variations in the input data to the optical model.

ISSN:0143-1161    

DOI:10.1080/01431169508954650

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor