This section outlines what is required for an organization to acquire, install and run the DIRSIG software.
At this time, RIT requires that all new users attend a 3-day training course that is comprised of classroom lectures describing how the model works and hands-on lab tutorials. The DIRSIG model is a research-grade software package that can be very powerful when used correctly and very misleading when used incorrectly. The goal of the course is to make sure that all users have a theoretical and practical understanding of the model so that it is used correctly.
This course is offered based on demand and a course fee is required.
The DIRSIG model is currently distributed free of charge to U.S. Government Organizations and Contractors. Usage of the software is defined by the DIRSIG Software Agreement. This document can be acquired from the DIRSIG website. The DIRSIG Software Agreement must be signed and executed by an officer of the organization within which the software will be used. In general, the DIRSIG Software Agreement allows users to have access to a binary distribution of the DIRSIG model and to use the model to generate imagery and related data products.
DIRSIG is distributed as binary executables only for the following supported architectures:
Sun Microsystems UltraSparc Servers and Workstations running Solaris 2.9+ (machine must be up-to-date with all patches)
Silicon Graphics (SGI) Servers and Workstations running IRIX 6.X
Intel Pentium and AMD Athlon Workstations running the Linux 2.4+ Kernel and Glibc 2.0+ (for example, RedHat 8+, Suse 8+, etc.).
The host machine should have at least 512 MB of physical memory but ideally as much as 2 GB of physical memory for very large simulations.
The base installation requires approximately 1 GB of disk space. Since the type of simulations that are performed by different users varies, the amount of disk space required for the imagery generated by the model will also vary. A single image can be as small as a few hundred kilobytes and as large as several gigabytes depending on the spatial and spectral resolution.
In addition to the DIRSIG software, there are other supporting software applications that the user must have in place in order to use the DIRSIG model.
The MODTRAN model is an atmospheric radiative transfer model that is developed by the Air Force Research Laboratory (AFRL). This model is the predominant code used for the prediction of path radiances and path transmissions within the atmosphere. The model allows the user to create rich descriptions of the atmosphere including vertical profiles of the water vapor, ozone, aerosols, etc.
The DIRSIG model uses MODTRAN to build atmospheric tables which are used as part of the overall radiative transfer.
To get a copy of the model, search the INTERNET for the AFRL website and submit the required paperwork. The model is distributed as FORTRAN source code so you will need a FORTRAN compiler for the system on which the application will run.
The FASCODE model is another AFRL atmospheric radiative transfer model. This model is very similar to the aforementioned MODTRAN model except that it utilizes a line-by-line model rather than a band model. This means that the model has essentially arbitrary spectral resolution which makes it applicable for very high spectral resolution simulations. However, the model lacks the scattering support found in the MODTRAN model, so the user must be aware of the potential impact of using this model at shorter wavelengths (or longer frequencies).
The FASCODE model is almost required for anyone that will simulate long-wave infrared (LWIR) hyperspectral imaging systems since the resolution limit of MODTRAN in this region will limit the channel sizes that can be modeled.
To get a copy of the model, search the INTERNET for the AFRL website and submit the required paperwork. The model is distributed as FORTRAN source code so you will need a FORTRAN compiler for the system on which the application will run.
The imagery created by the DIRSIG model will need to be viewed and/or imported into external applications to be of value. The specific format of the image files are discussed (see Section 32.6), however, the DIRSIG model automatically creates additional header files that allow the images to be directly read by ENVI.
ENVI is a commercial image exploitation package that is developed by Research Systems, Inc (RSI). The package is widely used in the hyperspectral remote sensing community because it is particular adept at working with hyperspectral imagery and has a large number of popular hyperspectral image algorithms built in. If your organization does not have ENVI installed, you can download a free release of the software that provides very basic image viewing capabilities. This version of the software is called ENVI Freelook and can be found on the RSI website (http://www.rsinc.com).