Search results for "MODTRAN"
showing 10 items of 26 documents
Alg: a Toolbox for the Generation of Look-Up tables Based on Atmospheric Radiative Transfer Models
2018
Atmospheric radiative transfer models (RTMs) are software tools describing the radiation processes occurring on the Earth’s atmosphere. While the evolution of these tools have achieved better representations of the light-atmosphere interactions, the increase of complexity, interpretability and computation time bears implications towards practical applications in Earth observation. Despite of existing RTM-specific graphical user interfaces, none of these tools allow common streamlining model setup for a wide variety of atmospheric RTMs. In addition, the automatic generation of atmospheric look-up tables (LUTs) can hardly be done with the use of these graphical tools. This paper presents the …
Gradient-Based Automatic Lookup Table Generator for Radiative Transfer Models
2022
Physically based radiative transfer models (RTMs) are widely used in Earth observation to understand the radiation processes occurring on the Earth’s surface and their interactions with water, vegetation, and atmosphere. Through continuous improvements, RTMs have increased in accuracy and representativity of complex scenes at expenses of an increase in complexity and computation time, making them impractical in various remote sensing applications. To overcome this limitation, the common practice is to precompute large lookup tables (LUTs) for their later interpolation. To further reduce the RTM computation burden and the error in LUT interpolation, we have developed a method to automaticall…
Systematic Assessment of MODTRAN Emulators for Atmospheric Correction
2021
Atmospheric radiative transfer models (RTMs) simulate the light propagation in the Earth's atmosphere. With the evolution of RTMs, their increase in complexity makes them impractical in routine processing such as atmospheric correction. To overcome their computational burden, standard practice is to interpolate a multidimensional lookup table (LUT) of prestored simulations. However, accurate interpolation relies on large LUTs, which still implies large computation times for their generation and interpolation. In recent years, emulation has been proposed as an alternative to LUT interpolation. Emulation approximates the RTM outputs by a statistical regression model trained with a low number …
Emulation as an Accurate Alternative to Interpolation in Sampling Radiative Transfer Codes
2018
Computationally expensive radiative transfer models (RTMs) are widely used to realistically reproduce the light interaction with the earth surface and atmosphere. Because these models take long processing time, the common practice is to first generate a sparse look-up table (LUT) and then make use of interpolation methods to sample the multidimensional LUT input variable space. However, the question arise whether common interpolation methodsperform most accurate. As an alternative to interpolation, this paper proposes to use emulation, i.e., approximating the RTM output by means of the statistical learning. Two experiments were conducted to assess the accuracy in delivering spectral outputs…
<title>Temperature and emissivity retrieval from DAIS data: application to the DAISEX campaigns in Colmar (France) and Barrax (Spain)</title…
2001
In the present paper it is presented a methodology to calculate the surface temperature (ST) from the combination of the radiometric temperature in two different DAIS (Digital Airborne Imaging Spectrometer) thermal bands using split-window (sw) method. To get this objective the MODTRAN 3.5 radiative transfer code was used to predict radiance for DAIS channels 74 (8.75 µm), 75 (9.65 µm), 76 (10.48 µm), 77 (1 1.27 µm), 78 (12.00 µm) and 79 (12.67 µm) at different aircraft altitudes with the appropriate channel filter functions. In order to analyse atmospheric effects a set of radiosoundings that cover the variability of surface temperature and water vapour concentration on a world-wide scale …
A Split-Window Algorithm for Estimating LST From Meteosat 9 Data: Test and Comparison With Data and MODIS LSTs
2009
The main purpose of this letter is to give an operational algorithm for retrieving the land surface temperature (LST) using the Spinning Enhanced Visible and Infrared Imager data onboard the Meteosat Second Generation (MSG2) satellite. The algorithm is a split-window method using the two thermal infrared channels IR10.8 and IR12.0. The MODTRAN 4.0 code was used to obtain numerical coefficients of the algorithm proposed. The results show that for viewing angles lower than 50deg the algorithm is capable of producing LST with a standard deviation of 0.7 K and a root-mean-square error (rmse) of 1.3 K. The algorithm has been applied to a series of MSG2 images obtained from an MSG antenna system …
Validation of temperature-emissivity separation and split-window methods from TIMS data and ground measurements
2003
Abstract Land surface temperature retrieved with temperature-emissivity separation (TES) and split-window (SW) algorithms from six-channel Thermal Infrared Multispectral Scanner (TIMS) data in the HAPEX-Sahel experiment agreed with contemporaneous ground temperature measurements to within ±1 °C (TES and SW with channels at 10.8 and 11.7 μm, or SW-56). The SW algorithm used with TIMS channels at 8.4 and 8.7 μm (SW-12) underestimated ground temperatures by 2–5 °C. The TES method required atmospheric correction of at-sensor radiances, which was done with local radiosonde data and MODTRAN 4, and an empirical relationship between the spectral range of emissivity and its minimum value. Emissivity…
A simplified method for estimating the total water vapor content over sea surfaces using NOAA-AVHRR channels 4 and 5
2002
A simplified method for estimating the total amount of atmospheric water vapor, W, over sea surfaces using NOAA-AVHRR Channels 4 and 5 is presented. This study has been carried out using simulated AVHRR data at 11 and 12 /spl mu/m (with MODTRAN 3.5 code and the TIGR database) and AVHRR, PODAAC, and AVISO databases provided by the Louis Pasteur University (Strasbourg-France), NASA-NOAA, and Meteo France, respectively. The method is named linear atmosphere-surface temperature relationship (LASTR). It is based on a linear relationship between the effective atmospheric temperature in AVHRR Channel 4 and sea surface temperature. The LASTR method was compared with the linear split-window relation…
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…
Error sources on the land surface temperature retrieved from thermal infrared single channel remote sensing data
2006
In this paper, a theoretical study complementary to others given in the literature about the errors committed on the land surface temperature retrieved from the radiative transfer equation in the thermal infrared region by remote sensing techniques has been analysed. For this purpose, the MODTRAN 3.5 code has been used in order to simulate different conditions and evaluate the influence of several parameters on the land surface temperature accuracy: atmospheric correction, noise of the sensor, land surface emissivity, aerosols and other gaseous absorbers, angular effects, wavelength uncertainty, full‐width half‐maximum of the sensor and band‐pass effects. The results show that the most impo…