The DIRSIG User's Manual
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Chapter 34. File Formats

Table of Contents
34.1. ADB: Atmospheric Database
34.2. EMS: Spectral Emissivity Database
34.3. EXT: Spectral Extinction Database
34.4. DUMP: Custom AutoCAD export file
34.5. GAS: Gas Absorption Spectrum
34.6. GDB: Geometric Database
34.7. INT: Source Radiant Intensity
34.8. MAT: Material Database
34.9. ODB: Object Database
34.10. PGM: NetPBM Image File Format
34.11. PRF: Classic Platform Location/Orientation Data
34.12. PPD: Generic Platform Positioning Data
34.13. PSF: Detector Point Spread Function
34.14. Plume Release File
34.15. RSP: Sensor Response
34.16. WTH: Weather History

34.1. ADB: Atmospheric Database

The DIRSIG atmospheric database (ADB) file contains the irradiance the sources outside the atmosphere (Sun and Moon) and the transmission, scattered radiance and emitted radiance for paths with in the atmosphere. In addition to including SCENE and PLATFORM sections similar to the CFG file, the ADB file contains three unique sections:

This general format of the file is illustrated by the example below: 

DIRSIG_ADB                       (1)
SCENE {                          (2)
}

PLATFORM {                       (3)
    INSTRUMENT {                 (4)
        BAND_LIST  {             (5)
            BAND {               (6)
            }
        }
        FIELD_OF_VIEW {          (7)
        }
    }
}

SOURCE_PATHS {                   (8)
}

SENSOR_PATHS {                   (9)
}

DOWNWELLED_PATHS {               (10) 
}

(1)
File Identification Marker
(2)
Copy of SCENE section from CFG
(3)
PLATFORM section similar to CFG
(4)
INSTRUMENT section similar to CFG
(5)
BAND_LIST section similar to CFG
(6)
Spectral Bandpass of BAND #1
(7)
Field-of-view of the instrument
(8)
Start of the SOURCE_PATHS section
(9)
Start of the SENSOR_PATHS section
(10)
Start of the DOWNWELLED_PATHS section

34.1.1. PLATFORM Section

The PLATFORM section in the ADB file is similar to the one from the CFG file used to create it. The ADB version, however, contains only the spectral and geometry related items required to verify that the ADB is still valid for a given CFG when DIRSIG is actually run. The BAND_LIST section contains one BAND section for each sensor band in the CFG file. These BAND sections only contain the spectral bandpasses for each sensor band. In addition, the FIELD_OF_VIEW section appears in the ADB file, and it defines the angular field of view of the instrument derive from the various focal plane and optics measurements in the CFG file. 

PLATFORM {                              (1)
    INSTRUMENT {                        (2)
        BAND_LIST {                     (3)
            BAND {                      (4)
                MINIMUM_FREQUENCY = 750.0
                MAXIMUM_FREQUENCY = 1250.0
                DELTA_FREQUENCY = 2.0
            }                           (5)
            BAND {                      (6)
            }                           (7)
        }                               (8)
        FIELD_OF_VIEW {                 (9)
            MINIMUM_ZENITH = -12.00 
            MAXIMUM_ZENITH = 44.00 
            DELTA_ZENITH = 2.80 
        }                               (10)
    }                                   (11)
}

(1)
PLATFORM section similar to CFG
(2)
INSTRUMENT section similar to CFG
(3)
BAND_LIST section similar to CFG
(4)
Spectral bandpass of BAND #1
(5)
End of BAND section
(6)
Spectral bandpass of BAND #N
(7)
End of BAND section
(8)
End of BAND_LIST section
(9)
Field-of-view of the instrument
(10)
End of BAND_LIST section
(11)
End of INSTRUMENT section

34.1.2. SOURCE_PATHS Section

The SOURCE_PATHS section contains the exoatmospheric irradiance of the Sun and the Moon for the given time and location. This section also includes the transmission for both of these sources from space to the center of the scene. These values are tabulated spectrally in the SPECTRAL_DATA section in the following format:

VALUE Wavelength Sun Irradiance Sun Trans Moon Irradiance Moon Trans
UNITS µm W/(cm² µm) (unitless) W/(cm² µm) (unitless)

or

VALUE Frequency Sun Irradiance Sun Trans Moon Irradiance Moon Trans
UNITS cm^-1 W/(cm² µm) (unitless) W/(cm² µm) (unitless) 

SOURCE_PATHS {                  (1)
    SPECTRAL_DATA {             (2)
        750.0 1.4100e-07 7.5900e-02 1.1800e-14 1.4010e-01
        752.0 1.4200e-07 9.1800e-02 1.1900e-14 1.6310e-01
        .
        .  [lines deleted for documentation purposes]
        .
        1250.0 3.8100e-07 2.6910e-01 3.2000e-14 3.7170e-01
    }                           (3)
}                               (4)

(1)
Start of the SOURCE_PATHS section
(2)
Start of the SPECTRAL_DATA section
(3)
End of the SPECTRAL_DATA section
(4)
End of the SOURCE_PATHS section

34.1.3. SENSOR_PATHS Section

The SENSOR_PATHS section contains the transmission, scattered radiance and emitted radiance of the atmosphere along several paths viewed by the sensor. Paths between those listed in the file are interpolated. Each PATH section contains the zenith and azimuth angle of the path, and the distance to the ground for the path. The atmospheric values are tabulated spectrally in the SPECTRAL_DATA section in the following format:

VALUE Wavelength Scattered Emitted Transmission
UNITS µm W/(cm² µm) W/(cm² µm) (unitless)

or

VALUE Frequency Scattered Emitted Transmission
UNITS cm^-1 W/(cm³) W/(cm³) (unitless) 

SENSOR_PATHS {              (1)
    PATH {                  (2)
        ZENITH = -12.0000   (3)
        AZIMUTH = 0.0000    (4)
        GROUND_RANGE = 0.1789   (5)
        SPECTRAL_DATA {         (6)
            750.0 2.1049e-06 6.0870e-18 8.3720e-01
            752.0 2.4751e-06 7.3141e-18 8.0820e-01
            . 
            . [lines deleted for documentation purposes]
            . 
            1250.0 3.8149e-07 3.6013e-16 9.2390e-01
        }        (7)
    }            (8)
}                (9)

(1)
Start of SENSOR_PATHS section
(2)
Start of PATH section
(3)
Zenith angle of this path
(4)
Azimuth angle of this path
(5)
Range to ground [km] from sensor
(6)
Start of SPECTRAL_DATA
(7)
End of this SPECTRAL_DATA section
(8)
End of PATH section
(9)
End of SENSOR_PATHS section

34.1.4. DOWNWELLED_PATHS Section

The downwelled radiance from the sky down is computed for a discrete set of zenith and azimuth pairs. Rays intersecting the sky utilize the hemispherical sky map to interpolate values between the samples. The zenith dimension is sampled from 7.5 degrees to 92.5 degrees on 7.5 degree intervals. The azimuth dimension is sampled from 0.0 degrees to 330.0 degrees on 30.0 degree intervals. The atmospheric values are tabulated spectrally in the SPECTRAL_DATA section in the following format:

VALUE Wavelength Scattered Emitted
UNITS µm W/(cm³ µm) W/(cm³ µm)

or

VALUE Frequency Scattered Emitted
UNITS cm^-1 W/(cm³) W/(cm³) 

DOWNWELLED_PATHS {           (1)
    PATH {                   (2)
        ZENITH = 7.5000      (3)
        AZIMUTH = 0.0000     (4)
        SPECTRAL_DATA {      (5)
            750.0 9.9068e-06 4.4277e-16  
            752.0 9.6366e-06 5.2540e-16  
            .  
            . [lines deleted for documentation purposes]  
            .
            1250.0 2.4194e-06 2.2617-14  
        }                    (6)
    }                        (7)

    TOTAL {                  (8)
        SPECTRAL_DATA {      (9)
            750.0 1.1096e-05 3.8147e-16  
            752.0 1.0898e-05 4.6116e-16  
            .  
            . [lines deleted for documentation purposes]  
            .  
            1250.0 3.1028e-06 2.5654e-14  
        }                    (10)
    }                        (11)
}                            (12)

(1)
Start of DOWNWELLED_PATHS section
(2)
Start of PATH section
(3)
Zenith angle of this path
(4)
Azimuth angle of this path
(5)
Start of SPECTRAL_DATA section
(6)
End of this SPECTRAL_DATA section
(7)
End of this PATH section
(8)
Start of TOTAL section
(9)
Start of SPECTRAL_DATA section
(10)
End of this SPECTRAL_DATA section
(11)
End of this PATH section
(12)
End of DOWNWELLED_PATHS section

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