| Environments | PYTHON :: EASI :: MODELER |
| Quick links | Description :: Parameters :: Parameter descriptions :: Details :: Example :: Acknowledgements :: References :: Related |
| Back to top |
| Back to top |
gentp5(tape5, atmod, vwvcins, msalg, nstr, aermod, aodins, smrins, prex, wlenins, reflins, razins, vzains, szains, elevins, saltins, date)
| Name | Type | Caption | Length | Value range |
|---|---|---|---|---|
| TAPE5* | str | Output file name | 1 - | |
| ATMOD* | str | Atmospheric model | 3 - 3 | TRO | MLS | MLW | SAS | SAW | USS |
| VWVCINS | List[float] | Water vapor content interval and samples | 0 - 3 | |
| MSALG | str | Multiple scattering algorithm | 0 - 6 | ISAACS | DISORT Default: ISAACS |
| NSTR | List[int] | Number of streams for DISORT | 0 - 1 | 2 | 4 | 6 | 8 Default: 2 |
| AERMOD* | str | Aerosol model | 3 - 5 | RUR23|RUR05|MAR|URB|TRO|AFOG|RFOG|DES |
| AODINS | List[float] | Aerosol optical depth range interval and samples | 0 - 3 | |
| SMRINS | List[float] | Surface meteorological range interval and samples | 0 - 3 | |
| PREX | str | Aerosol stratospheric profile and extinction type | 0 - 4 | BSBS|MVAV|HVFV|MVFV|MVBS|HVBS|EVFV Default: BSBS |
| WLENINS* | List[float] | Wavelength interval and samples | 3 - 3 | |
| REFLINS* | List[float] | Reflectance interval and samples | 3 - 3 | |
| RAZINS* | List[float] | Relative view-solar azimuth interval and samples | 3 - 3 | |
| VZAINS* | List[float] | View zenith angle interval and samples | 3 - 3 | |
| SZAINS* | List[float] | Solar zenith angle interval and samples | 3 - 3 | |
| ELEVINS* | List[float] | Scene elevation interval and samples | 3 - 3 | |
| SALTINS* | List[float] | Sensor altitude interval and samples | 3 - 3 | |
| DATE | List[int] | Scene acquisition date (day, month, year) | 0 - 3 | Default: 3,4 |
| Back to top |
TAPE5
Specifies the name of the output MODTRAN4 "tape5" file to be created.
If no leading path is specified, the file will be created in the current working directory.
ATMOD
Specifies the type of atmospheric model used to evaluate the MODTRAN4 CARD 1 "MODEL" column.
VWVCINS
Specifies the atmospheric water vapor content interval endpoints (in g/cm^2) and the number of samples. An endpoint value e must be such that e >= 0. This value modifies the selected atmospheric model used to evaluate the MODTRAN4 CARD 1A "H2OSTR" column.
If this parameter is not specified, the "tape 5" file will represent a single water vapor content sample for which the value is the default value for the selected atmospheric model.
MSALG
Specifies the multiple scattering sub-algorithm used to evaluate the MODTRAN4 CARD 1A "DIS" column.
NSTR
Specifies the number of streams to be used by the discrete ordinates radiative transfer sub-algorithm. This value is used to evaluate the MODTRAN4 CARD 1A "NSTR" column. If the Multiple Scattering Algorithm is not specified as "DISTORT", this parameter is ignored.
A value of 2, 4, 8, or 16 may be specified; the default is 2. Higher values result in longer computation time.
AERMOD
Specifies the type of aerosol model used for boundary layer (0 to 2km) calculations. This value is used to evaluate the MODTRAN4 CARD 2 "IHAZE" column.
If the surface meteorological range (SMRINS) is not specified, the "tape5" file will represent a single-surface meteorological range sample for which the value is the default value for the aerosol model.
AODINS
Specifies the aerosol optical depth range interval at 550nm endpoints (unitless) and the number of samples. An endpoint value e must be such that 0 <= e <= 2.
AODINS is used as an alternative to SMRINS for evaluating the MODTRAN4 CARD 2 "VIS" column; only one these two parameters may be specified.
If neither AODINS nor SMRINS is specified, the "tape5" file will represent a single-surface meteorological range sample for which the value is the default value for the aerosol model.
SMRINS
Specifies the surface meteorological range interval endpoints (in km) and the number of samples. An endpoint value e must be such that 0 < e.
SMRINS is used as an alternative to AODINS for evaluating the MODTRAN4 CARD 2 "VIS" column; only one these two parameters may be specified.
If neither AODINS nor SMRINS is specified, the "tape5" file will represent a single-surface meteorological range sample for which the value is the default value for the aerosol model.
PREX
Specifies the aerosol profile and stratospheric aerosol extinction types. Modifies the selected aerosol model.
This value is used to evaluate the MODTRAN4 CARD 2 "IVULCN" column. If not specified, the "background" stratospheric profile and extinction type is used.
WLENINS
Specifies the wavelength interval endpoints (in nanometers) and the number of samples.
An endpoint value e must be such that e >200nm. This value is used to evaluate the MODTRAN4 CARD 4 "V1", "V2", and "DV" columns.
REFLINS
Specifies the reflectance interval endpoints (in percentage) and the number of samples.
An endpoint value e must be such that 0 < e <= 1. This value is used to evaluate the MODTRAN4 CARD 1 "SURREF" column.
RAZINS
Specifies the relative view-solar azimuth (solar azimuth minus view azimuth) interval endpoints (in degrees) and the number of samples.
An endpoint value e must be such that -360 <= e <= 360. This value is used to evaluate the MODTRAN4 CARD 3A2 "PARM1" column.
VZAINS
Specifies the view zenith angle interval endpoints (in degrees) and the number of samples.
An endpoint value e must be such that 90 <= e <= 180. This value is used to evaluate the MODTRAN4 CARD 3 "ANGLE" column. A horizontal view direction has a zenith angle of 90deg, and a vertical down view direction has a zenith angle of 180deg.
SZAINS
Specifies the solar zenith angle interval endpoints (in degrees) and the number of samples.
An endpoint value e must be such that 0 <= e <= 90. This value is used to evaluate the MODTRAN4 CARD 3A2 "PARM2" column.
ELEVINS
Specifies the scene elevation interval endpoints (in meters with respect to the WGS84 vertical datum) and the number of samples.
This value is used to evaluate the MODTRAN4 CARD 3 "H2" and CARD 2 "GNDALT" columns.
SALTINS
Specifies the sensor altitude interval endpoints (in meters with respect to the WGS84 vertical datum) and the number of samples.
This value is used to evaluate the MODTRAN4 CARD 3 "H1" column.
DATE
Specifies the date (day, month, year) that MODTRAN4 will use to calculate the sun-to-Earth distance. If this parameter is not specified, a mean sun-to-Earth distance will be used instead, equivalent to using the 3rd of April (in non-leap years) as the date. The year component of the date may be omitted.
| Back to top |
GENTP5 is designed to be used in combination with the MODTRAN4 program and GENRLUT to produce a radiance lookup table (RLUT) for the atmospheric transformation of remotely sensed images. GENTP5 has been tested with Versions 2 and 3 of the MODTRAN4 program.
The "tape5" file generated by GENTP5 holds input parameter values (sets of "cards" in MODTRAN terms) for one or more MODTRAN4 runs. Multiple MODTRAN4 runs correspond to multiple samples along one or more RLUT dimensions other than the wavelength dimension. The multiple MODTRAN4 runs are actually made in one execution of the the MODTRAN4 program.
The "tape7" file generated by the MODTRAN4 program contains the results of the MODTRAN4 runs. GENRLUT transforms this file to an RLUT.
GENTP5 provides two ways of specifying the MODTRAN4 CARD 2 "VIS" parameter: by using an aerosol optical depth and by using a surface meteorological range. As those two parameters affect the same MODTRAN4 setting, only one of them may be specified for a GENTP5 execution. If you denote the surface meteorological range with VIS and the aerosol optical depth with AOD, the AOD-to-VIS mapping is accomplished using the following third-order polynomial approximation:
1/VIS = -0.014267*AOD^3 + 0.062699*AOD^2 + 0.117591*AOD - 0.001074
GENTP5 does not give the user access to all of the MODTRAN4 parameters and options; only those that match a practical atmospheric correction method are accessible. There is no dependence on difficult-to-obtain field measurements. Also, GENTP5 makes some choices to avoid extra computation that would contribute little to the usefulness of the RLUT generated by GENRLUT.
| Back to top |
This example demonstrates the use of GENTP5, the MONDTRAN4 program, and GENRLUT in generating a radiance lookup table (RLUT) suitable for the transformation of the cuprad.pix radiance data set to a reflectance data set. The radiance-to-reflectance transformation is achieved by using ATRLUT together with the generated radiance lookup table.
The above were taken from the navigation data that accompanied the original data distribution (see the README.txt file for cuprad.pix) and are part of the image metadata held in cuprad.pix.
A nominal scene elevation of 1,524m will be used (see References).
Based on the nominal location and time, we will use the midlatitude summer atmospheric model and the desert aerosol model. We do not have a surface meteorological range value, nor an aerosol optical depth value, so we will allow MODTRAN4 to use the visibility it associates with the desert aerosol model by default.
The atmospheric conditions are noted as 'clear' by the pilot in the distribution metadata, so we will select 'background' stratospheric profile and extinction.
The data set consists of 224 bands with center wavelengths from 369.85nm to 2506.81nm and a nominal FWHM of 10nm. We will specify a wavelength interval of [355nm, 2515nm] and 2161 samples, to allow reliable resampling to the sensor response profile, which is stored in the cupref.pix metadata.
The AVIRIS overall field of view is 15deg to either side of the central optical axis (this information is stored in the cupref.pix image metadata). Therefore, we will specify a view zenith angle interval of [165deg,180deg]. We will specify four samples in this interval.
Based on a nominal heading of 179.8deg and the knowledge that AVIRIS is a whiskbroom sensor, we determine that the view azimuth is 179.8deg +/- 90deg, or is either 89.8 or 269.8. The view-solar azimuth is positive clockwise starting from the view azimuth direction, and is thus equal to the solar azimuth minus the view azimuth. Therefore, the relative view-solar azimuth is either (189.0 - 89.8)deg = 99.2deg or (189.0 - 269.8)deg = -80.8deg. We will specify a relative view-solar azimuth angle interval of [-80.8deg, 99.2deg] and three samples to account for the nadir pixel.
We will specify the reflectance interval of [0.05, 0.60] and two samples, which is typically used by this atmospheric transformation method.
We have no records of the atmospheric water vapor content. We will allow MODTRAN4 to use the value that it associates with the midlatitude summer atmospheric model by default. Alternatively, GENAWVC can be used to analytically extract the atmospheric water vapor content from the image data.
from pci.gentp5 import gentp5
tape5 = "tape5" # write output to a file named "tape5"
# in current working directory
atmod = "MLS" # midlatitude summer atmospheric model
vwvcins = [] # use default for midlatitude summer
msalg = "ISAACS" # use ISAACS scattering model
nstr = [] # ignored for ISAACS scattering model
aermod = "DES" # desert aerosol model
aodins = [] # use default visibility range for desert
smrins = [] # use default visibility range for desert
prex = "BSBS" # background stratospheric profile and extinction
wlenins = [355, 2515, 2161] # 2161 samples in [355nm, 2515nm]
reflins = [0.05, 0.60, 2] # two samples: 0.05 and 0.60
razins = [-80.8, 99.2, 3] # three samples: -80.9deg, 9.2deg, and 99.2deg
vzains = [165, 180, 4] # four samples in [165deg, 180deg]
szains = [14.4, 14.4, 1] # one sample: 14.4deg
elevins = [1524, 1524, 1] # one sample: 1524m
saltins = [21036, 21036, 1] # one sample: 21036m
date = [19,6,1997] # set acquisition date to 19 June, 1997
gentp5( tape5, atmod, vwvcins, msalg, nstr, aermod, aodins, smrins,
prex, wlenins, reflins, razins, vzains, szains, elevins,
saltins, date )
| Back to top |
PCI Geomatics received financial support from the Canadian Space Agency/L'Agence Spatiale Canadienne through the Earth Observation Application Development Program (EOADP) for the development of this software, under contract 9F028-0-4914/09.
| Back to top |
R.A. Neville et al., Spectral Unmixing of Hyperspectral Imagery for Mineral Exploration: Comparison of Results from SFSI and AVIRIS, "Can. J. Remote Sensing," Vol.29, No.1, pp. 99-110, 2003.
Berk, A. et al., 1999, "Modtran4 User's Manual", Air Force Research Laboratory, Space Vehicles Directorate, Air Force Materiel Command, Hanscom AFB, MA
Matthew, M.W. et al. "Status of Atmospheric Correction Using a Modtran4-Based Algorithm", SPIE Proceeding, Algorithms for Multispectral, Hyperspectral, and Ultraspectral Imagery VI, Volume 4049, April 2000.
© PCI Geomatics Enterprises, Inc.®, 2024. All rights reserved.