Search results for "EMISSIVITY"
showing 10 items of 136 documents
Recovering Surface Temperature and Emissivity from Thermal Infrared Multispectral Data
1998
Abstract In 1992 Thermal Infrared Multispectral Scanner (TIMS) data were acquired from the NASA C-130 aircraft over the Sahelian region of West Africa as part of the Hydrological and Atmospheric Pilot Experiment in the Sahel (HAPEX). TIMS measures the radiation from the surface modified by the atmosphere in six channels located between 8 mm and 12.5 μm in the thermal infrared. By using a variety of techniques it is possible to extract both the surface temperature and surface emissivity from the areas over which TIMS data were acquired. One such technique was tested with the data acquired during this experiment. Several TIMS images of both the east and west central sites on 2 and 4 September…
Improved Temperature and Emissivity Separation Algorithm for Multispectral and Hyperspectral Sensors
2017
The Temperature and Emissivity Separation (TES) algorithm was originally developed for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER). This paper focuses on improving the TES algorithm. The main modification is the replacement of the normalized emissivity module with a new module, which is based on the smoothing of spectral radiance signatures. Smoothing is performed by estimating emissivity using an optimized approximation of the relationship between brightness temperature and emissivity. The improved TES algorithm, which is called Optimized Smoothing for Temperature Emissivity Separation (OSTES), was first tested on simulated data from three different sensors, …
Soil emissivity and reflectance spectra measurements
2009
We present an analysis of the laboratory reflectance and emissivity spectra of 11 soil samples collected on different field campaigns carried out over a diverse suite of test sites in Europe, North Africa, and South America from 2002 to 2008. Hemispherical reflectance spectra were measured from 2.0 to 14 microm with a Fourier transform infrared spectrometer, and x-ray diffraction analysis (XRD) was used to determine the mineralogical phases of the soil samples. Emissivity spectra were obtained from the hemispherical reflectance measurements using Kirchhoff's law and compared with in situ radiance measurements obtained with a CIMEL Electronique CE312-2 thermal radiometer and converted to emi…
Soil Moisture Effect on Thermal Infrared (8–13-μm) Emissivity
2010
Thermal infrared (TIR) emissivities of soils with different textures were measured for several soil moisture (SM) contents under controlled conditions using the Box method and a high-precision multichannel TIR radiometer. The results showed a common increase of emissivity with SM at water contents lower than the field capacity. However, this dependence is negligible for higher water contents. The highest emissivity variations were observed in sandy soils, particularly in the 8-9-μm range due to water adhering to soil grains and decreasing the reflectance in the 8-9-μm quartz doublet region. Thus, in order to model the emissivity dependence on soil water content, different approaches were st…
Laboratory calibration and field measurement of land surface temperature and emissivity using thermal infrared multiband radiometers
2019
Accurate ground measurements of land surface temperature (LST) are necessary for validating satellite LST products. In order to provide reliable data, ground radiometers must be calibrated with reference to an international standard, and radiometric temperatures must be corrected for land surface emissivity. As opposed to water, land surface emissivity is not usually known for many ground covers, so an emissivity value has to be assumed, assigned from spectral emissivity libraries or measured for each land cover and spectral band considered. The aim of this study is to show the laboratory calibration and the methodology for simultaneous field measurements of LST and emissivity employed in t…
Angular variation of thermal infrared emissivity for some natural surfaces from experimental measurements
2008
Multiangle algorithms for estimating sea and land surface temperature with Along-Track Scanning Radiometer data require a precise knowledge of the angular variation of surface emissivity in the thermal infrared. Currently, few measurements of this variation exist. Here an experimental investigation of the angular variation of the infrared emissivity in the thermal infrared (8-14-microm) band of some representative samples was made at angles of 0 degrees-65 degrees (at 5 degrees increments) to the surface normal. The results show a decrease of the emissivity with increasing viewing angle, with water showing the highest angular dependence (approximately 7% from 0 degrees to 65 degrees views).…
In-scene atmospheric correction of hyperspectral thermal infrared images with nadir, horizontal, and oblique view angles
2012
Atmospheric corrections for hyperspectral thermal images acquired with nadir, horizontal, and oblique views have typically relied on atmospheric modelling software, such as Moderate Resolution Atmospheric Transmission MODTRAN, to estimate atmospheric parameters. Data-only corrections, which require only information from the scene, are more versatile and less labour intensive, but do not yet seem to have been applied to horizontal and oblique views. Here, we apply, and modify where necessary, one published data-only algorithm in-scene atmospheric correction ISAC to nadir, horizontal, and slanted views The Aerospace Corporation's Spatially Enhanced Broadband Array Spectrograph System SEBASS a…
Land surface emissivity retrieval from different VNIR and TIR sensors
2008
This paper discusses the application and adaptation of two existing operational algorithms for land surface emissivity (epsiv) retrieval from different operational satellite/airborne sensors with bands in the visible and near-infrared (VNIR) and thermal IR (TIR) regions: (1) the temperature and emissivity separation algorithm, which retrieves epsiv only from TIR data and (2) the normalized-difference vegetation index thresholds method, in which epsiv is retrieved from VNIR data.
Estimating the difference between brightness and surface temperatures for a vegetal canopy
1995
Abstract The difference between the surface temperature T S and the brightness temperature T b , which can be measured with a thermal infrared radiometer, has been calculated for different surface emissivity values and different atmospheric conditions. These calculations show that T s − T b is often significant even for high surface emissivities and that the spectral band in which the measurements are performed is a key factor in the interpretation of T s − T b . In particular, it is not a simple matter to use the characterisation of the whole spectrum atmospheric radiation to derive T s from T b when the measurements are performed in the 8–14 μm atmospheric window.
Emissivity mapping over urban areas using a classification-based approach: Application to the Dual-use European Security IR Experiment (DESIREX)
2012
Abstract In this work a methodology to provide an emissivity map of an urban area is presented. The methodology is applied to the city of Madrid (Spain) using data provided by the Airborne Hyperspectral Scanner (AHS) in 2008. From the data a classification map with twelve different urban materials was created. Each material was then characterized by a different emissivity, whose values were obtained from the application of the TES algorithm to in situ measurements and values extracted from the ASTER spectral library. This new emissivity map could be used as a basis for determining the temperature of the city and to understand the urban heat island effect in terms of spatial distribution and…