Key Input Variables

Once defined the General Configuration of a LUT, the second step consists on introducing the Key Input Variables for the selected atmospheric RTM.

When opening this step, ALG will automatically read, from the RTMconf.xml file, all the attributes associated with the key input variables of the selected RTM. The user will have access to more or less key input variables depending on the selected user level.
Note: Read the "Key Input Variables" sub-section of the selected Third-party Software (RTMs) for more information about the key input variables.

In case of a Latin Hypercube or Sobol/Halton sequence distribution with a stop condition based on the maximum # of LUT samples option, the user must introduce the total # of grid points to be introduced in the LUT. This parameter will not be visible is the distribution is Manual (gridded) sampling or if the stop condition is selected on the cross-validation option. See General Configuration for further information.

To introduce the LUT variables, the user starts by clicking on one of the variable Groups (i.e., Atmospheric, Aerosols or Geometric) at the top-left of the screen. Once the group is selected, the associated variables will be displayed on the Parameter menu. The user can then select one of these variables in order to proceed introducing its values for the LUT, which will differ depending on the parameter type (i.e., discrete or continuous).

  • For discrete variables, an associated menu will be displayed at the bottom-left corner. This menu will contain the available options that can be selected. On dynamic variables, the user may select more than one option by pressing Ctrl.+left click.

    A special case for user-defined aerosol models based on OPAC database is further described in Input User-Defined OPAC Aerosols.
  • For continuous variables, an associated panel will be displayed at the bottom-left corner. The user must select the min/max values and, only for Manual (gridded) distribution, the # of samples (>2) and distribution (linear, exponential, logarithmic or cosine). The Preview button will allow the user to see a plot with the introduced values.

    ALG will automatically check that the introduced values are within the valid range predefined in the RTMconf.xml file, prompting an error message and correcting the out-of-range values.

After introducing the desired values for the selected key input variable, the user must press on the Add parameter button (or press ) so the atmospheric LUT will include this variable values. This will add the selected variable and its values on the table at the left of the LUT configuration panel.

The user can remove one or more of these parameters from the table by selecting them () and pressing the Remove button. Also, the introduced variable values can be edited on the corresponding Values cell on the table. Notice here that the values must be comma-separated.

The user should repeat these steps for each new variable to be added in the LUT. The default value in the RTMconf.xml file will be assigned for all those variables that are not introduced by the user.

Alternatively, the user can press the button to add all the variables for the selected user level. This will fill the table with the min/max values for continuous variables and default values for discrete variables.

Once introduced all the LUT input key variables, the user should click on the Next button at the bottom-left corner to proceed defining the spectral configuration of the LUT output atmospheric transfer functions. This will update the LUT configuration .xml file (e.g., C:\ALG\LUTs_folder\LUTfile.xml), storing these key input variables for their later use in the execution of the atmospheric RTMs and generation of input data.