WSF_TABULAR_ATTENUATION

attenuation_model WSF_TABULAR_ATTENUATION
attenuation_model <name-or-type> WSF_TABULAR_ATTENUATION
   attenuation ...
   adjustment_factor ...
   sort_end_points ...
   two_way_attenuation ...
   spectral_data_conversion ...
end_attenuation_model

WSF_TABULAR_ATTENUATION is an attenuation_model that allows the user to define attenuation using a table.

attenuation <table-value>

Specifies a table that defines the attenuation values. The table must be a function of at least three independent variables:

  • altitude, elevation_angle and slant_range

  • altitude_1, altitude_2 and ground_range

It may additionally include ‘frequency’ as an additional independent variable.

Default: none (must be specified)

adjustment_factor <value>

Specifies a multiplier to be applied to returned values. This would typically be used to account for the fact that values integrated over a wide band (i.e.: visual) represent an average that may include many ‘dead-zones’ that the sensor may exclude. Thus, the effective transmittance may be higher.

Note

The return values are transmittance, so to increase transmittance specify a factor greater than one.

Default: 1.0 (no adjustment)

sort_end_points <boolean-value>

Specifies end-points (source and target points) for a given interaction can be logically interchanged so the path goes from the highest object to the lowest object. This would be applicable if the attenuation values are independent of direction. This would allow a table to be computed for air-to-ground purposes to also be used for ground-to-air purposes.

Default: false

two_way_attenuation <boolean-value>

Specifies if the table values represent two-way attenuation (transmitter-to-target-to-receiver).

Default: false (the table values represent one-way attenuation)

spectral_data_conversion … end_spectral_data_conversion

This command is used to convert spectral data produced by a program like MODTRAN into a form that can be used as input for the attenuation command.

This command is used separately from the actual run of a simulation that employs the model. For instance, one would first convert the file executing the following input within mission:

attenuation_model CONVERT WSF_TABULAR_ATTENUATION
   spectral_data_conversion
      sensor_to_target_transmittance example_stt.plt
      output                         example.txt
   end_spectral_data_conversion
end_attenuation_model

The resulting converted data would then be used as an attenuation model in a sensor:

attenuation_model EXAMPLE WSF_TABULAR_ATTENUATION
   attenuation file example.txt
end_attenuation_model
sensor_to_target_transmittance <filename>

Specifies the name of the file which contains the raw spectral sensor-to-target transmittance as a function of observer altitude and elevation angle and slant range to the target. Using the current processes, this file name will be of the form <filename>_stt.plt.

Default: none - this is required.

target_to_background_radiance <filename>

Specifies the name of the file which contains the raw spectral target-to-background radiance as a function of observer altitude and elevation angle and slant range to the target. Using the current processes, this file name will be of the form <filename>_tbr.plt.

If this file is NOT provided, the output will simply contain the integrated transmittance for each point. If the file is provided then the output will contain the ‘line-of-sight atmospheric transmittance’ or ‘contrast transmittance’ needed by some sensor models.

Default: none - the output contains the integrate transmittance.

spectral_response_curve … end_spectral_response_curve

This defines the response of the sensor as a function of wavelength. The curve is defined as a series of points where each point is defined as:

wavelength response

where the first item is the wavelength (with units) and the second item is the response for that wavelength. The response must be in the range [0 .. 1]. At least two points must be specified and the points must be in monotonically ascending of wavelength.

Default: Uniform response of 1.0 for all wavelengths contained in the input files

output <filename>

Specifies the name of the file to which the converted results are to be written. The file can be used at the argument for the attenuation command (See the example at the start of the section.)

Default: none - must be provided.