ISSN:0143-1161    

DOI:10.1080/01431168708954739

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Due to increased concern over the climatic and economic impact of fires associated with deforestation and seasonal burning, most of which occurs in remote parts of the worid, it is necessary to find ways to effectively monitor such activity. The 3.8μm channel on board the National Oceanic and Atmospheric Administration's polar-orbiting satellites is very sensitive to high temperature sources such as fires. Case studies in Mexico, Brazil, Mozambique and the Soviet Union have been selected to demonstrate the utility of this channel for fire detection. With the fire detection capability of the 3.8 μm channel and the daily global coverage, it is possible to monitor world-wide fire activity.

ISSN:0143-1161    

DOI:10.1080/01431168708954740

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Spectral separability analysis of various tropical forest cover classes as recorded on Landsat MSS data were carried out for two test areas of northeastern India. The results indicated that two density classes of forests and two edaphic forest types formed spectrally separable classes but some of the important physiognomic units could not be reliably separated using Landsat MSS data in a spectrally complex tropical forest environment.

ISSN:0143-1161    

DOI:10.1080/01431168708954741

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Natural thermal emission in the 8-12 μm band as well as emission or diffusion of microwaves at low frequencies are known to be strongly correlated with the soil surface water content. Theoretical studies of the interaction between the soil/plant system and the atmosphere have shown that such measurements may be used to monitor the soil water budget. Experimental results from an airborne campaign are presented here. The surface temperature and radar cross-section spatial properties and their interrelations are examined for very different situations (wet and dry, bare and vegetated). It is shown that, as far as large-scale applications are concerned, the field scale can be considered as homogeneous for both measurements and that it is possible to derive meaningful regional information from measurements at that scale. Therefore, at least for the test region, a high spatial resolution (of microwaves and thermal infrared measurements) is not required for the monitoring of surface soil moisture and thermal equilibrium for this 10-day period.

ISSN:0143-1161    

DOI:10.1080/01431168708954742

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Although it has been known for quite some time that individual leaves display non-Lambertian scattering at wavelengths of strong absorption in the visible part of the spectrum, while displaying near-Lambertian behaviour at wavelengths of little absorption in the near-infrared, this is widely ignored in geobotanical remote sensing investigations. Preliminary data show that non-Lambertian behaviour may have a significant effect on the ratio of infrared/red reflectance with changing illumination and observation angles, but little or no efTect on the location of the steep rise in reflectance from the red to the infrared (‘red edge’). These results indicate the need for a complete assessment of directional scattering from different vegetation and canopy types, and strongly suggest the need for caution in interpretation of observational data taken without regard for illumination and observation angles.

ISSN:0143-1161    

DOI:10.1080/01431168708954743

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The spectral components analysis identities, LAI/VI × APAR/LAI = APAR/VI and LAI/VI × YIELD/LAI = YIELD/VI, where VI denotes any one of several spectral vegetation indices available, LAI is the leaf area index, APAR is the absorbed photosynthetically active radiation and YIELD is the saleable plant part (grain, fibre or root), express the information conveyed by canopies about their development, response to stresses and yield capability. The rationale includes the concepts that vegetation indices adequately measure the amount of photosynthetic-ally active tissue in plant canopies and that high yields cannot be achieved unless growing conditions permit canopies to develop that effectively intercept the available light during reproduction. For wheat, cotton and maize the coefficients of determination (r2) usually exceeded 0.90 for exponential, power or linear expressions relating the numerator (dependent variable,y) to the denominator (x) variable of each term in the first equation. Results show that APAR can be reliably estimated from VI, and that the relation is nearly linear. The equations help to quantify remote assessments of crop productivity, to unify field-observed interrelations among LAI, APAR and YIELD and to validate remotely observable LAI and APAR inputs for plant process crop growth and yield models, or for growth analysis.

ISSN:0143-1161    

DOI:10.1080/01431168708954744

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In an ideal world (for remote sensing) the nature of the surface would be completely specified by the spectral signature. In the real world, however, the compexity of natural surfaces, effects of the atmosphere and ambiguity of the spectral signatures act to limit remote sensing without ground truth to applications that demand little from the radiometric quantities in the data. Ground surveys are complementary to the synoptic overview provided by satellites, helping to link the image data to the surface context. This paper reviews the purposes and problems of such ground surveys and examines in particular the nature of the relationship between the object of inquiry and the spectral signature. The investigator must select object variables that are both appropriate to the application and well matched to the spectral signature. This problem is discussed in the context of vegetation canopies.

ISSN:0143-1161    

DOI:10.1080/01431168708954745

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The archaeological study of standing buildings is often compounded by the need to examine hidden areas and by the loss of information from objects due to the action of weathering and decay. It is not always possible or desirable to examine the fabric ‘destructively’ or to remove fittings to the laboratory for examination. Research into the development and application of ground-based remote sensing techniques has produced significant results, enabling the in situ non-destructive survey of historic buildings and their fittings. Archaeological sites under excavation have also been surveyed using similar principles. This paper reviews the problems and methodology employed to date.

ISSN:0143-1161    

DOI:10.1080/01431168708954746

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

The application of nitrogen to small plots of barley increased leaf chlorophyll concentrations and produced darker green canopies. Leaf pigment concentrations were estimated independently of crop biomass using a band-pass radiometer to view the canopy at an oblique angle to minimize the influence of the soil background.

ISSN:0143-1161    

DOI:10.1080/01431168708954747

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

At a first stage of development, ground truth is gathered in conjunction with radar data in order to establish statistical correlations between observed backscatter and properties of the irradiated surface. Significant correlations have been shown to exist between backscatter and many geophysical quantities; for example scatterometer measurements over the ocean can be used to infer wind speed, synthetic aperture radar (SAR) measurements over woodland can allow the separation of tree species, etc. Once statistical relationships are established, the next stage is to try to understand the physics underlying the relationship, both because of its intrinsic interest and because of the need to optimize system performance for particular applications. This places a second role on ground truth, since it must be used to validate the physical theories stemming from it. Microwave scattering from land surfaces is a topic of growing interest as we look towards land observation missions within the coming decade. Several theories have been proposed to account for scattering from surfaces of a vegetation layer, but none of these has been rigorously tested. If they are to contribute effectively to future land missions, it is essential that such testing be carried out. The first section of this paper describes the requirements such testing will put on ground measurements, and tries to identify whether such measurements are feasible. Microwave scattering mechanisms from the sea surface, and particularly their effects on SAR images of waves, and clutter-statistics in SAR sea-surface images are still a matter of some debate. The second section of this paper outlines the problems inherent in sea imaging with SAR and describes experiments that need to be carried out in order that these questions can be resolved.

ISSN:0143-1161    

DOI:10.1080/01431168708954748

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor