This chapter discusses how the polarization aspects of DIRSIG4 work. This topic is described in a separate chapter because to model a polarized system encompasses several areas of the DIRSIG modeling process. As you will see, when modeling a polarized environment the atmosphere, the materials and the sensor are configured differently. This chapter will describe polarization specific features of these DIRSIG components which are otherwise not discussed in the detailed sections of the manual dedicated to those components.
This chapter discusses how a user can set up a DIRSIG4 simulation that will produce polarized imagery. At this time, the DIRSIG4 user interface utilizes the same configuration files that DIRSIG3 used. In some cases, there are new options or fields that can be used to access new features, but DIRSIG4 should run with a DIRSIG3 configuration file without any changes. The following sections will outline optional user inputs that are used to directly support polarization modeling.
To correctly model a polarized scenario you will need to have access to the Air Force Research Laboratory's (AFRL's) MODTRAN-P atmospheric radiation transfer model, which is used by DIRSIG to compute atmospheric properties that are polarized. However, the MODTRAN-P model is available only to a select beta-testing community. If you are not already a part of this user community, it is unlikely that you will be able to gain access to this modeling tool.