Chapter 4. Getting Started
- Table of Contents
- 4.1. Using DIRSIG
- 4.2. Framing Array Tutorial
- 4.3. Pushbroom Scanner Tutorial
This chapter of the manual is designed to get you familiar with the DIRSIG model by walking the user through two tutorials. In these tutorials, not every aspect of the model will be discussed in detail to keep the presentation simple. The detailed features of the model can be explored in the In-Depth Material part of the manual.
The general model process can be summarized in the 4-step process outlined in Figure 4-1. During the tutorials in this section, the user is guided through these last 3 steps. The construction of new scenes is a complex and potentially time consuming process that was avoided in these tutorials to keep the presentation simple. The basics of scene construction are discussed in the chapter Basic Scene Construction.
4.1. Using DIRSIG
4.1.1. Starting the user interface
The DIRSIG model uses a single input file to describe the parameters for a given simulation (although that input file may reference a large number of auxiliary files). This input file is referred to as the DIRSIG configuration file, or CFG file (denoted with a .cfg extension). The CFG file is an ASCII file that can be easily edited by the user. The syntax of this file is described in detail in Input Configuration File.
The starting point for the GUI interface is a tool called cfg_edit. This tool allows the user to create new CFG files or edit existing CFG files. The cfg_edit tool will also start up the tape5_edit tool (so that the user can manipulate the MODTRAN input "tape5"' file) and the mat_edit tool (to edit and manipulate the material database file). If your environment has been correctly set-up, then you should be able to start the main GUI editor from the command line as follows:
prompt> cfg_edit
The cfg_edit main window consists of a series of buttons that open additional windows which address specific aspects of the model (see Figure 4-2). The buttons that are disabled (disabled buttons have lighter text) are enabled by enabling more complex aspects of the model. During the course of this introductory level tutorial, we will access most of basic aspects of the model.
The buttons on the cfg_edit main window are named after the eight (8) major sections of the DIRSIG input file. A brief overview of each component is provided below, including references to any chapters in In-Depth Material that discuss these components in detail.
| Paths: | The search paths for the various auxiliary input files needed by the model. |
| Scene: | The physical contents, location and time for the simulation. |
| Environment: | The environmental conditions for the simulation including the atmospheric optical properties and the meteorological history. |
| Platform: | The sensing platform used to acquire imagery of the scene. This includes descriptions of the platform's location and orientation as well as a rigorous specification of the imaging instrument on-board the platform. This component is discussed in detail in Chapter Platform Modeling. |
| Options: | Controls over the run-time options of the model. This includes the ability to enable and disable specific sub-models and control the model outputs. |
| Truth Images: | The user-selectable list of truth images that can be generated at run-time. The truth images can include useful analysis tools such as classmaps and per-pixel temperature maps. |
| Maps: | An optional section that allows the user to configure and apply various material and property maps to elements in the scene. This includes features such as texture and material mixture maps. This component is discussed in detail in Chapter Property Mapping Techniques. |
| Plume: | The interface for specifying the inputs to the EPA/JPL plume Gaussian factory stack plume model. This component is discussed in detail in Chapter Gas Plume Modeling. |
After each of the model components have been configured to create a simulation scenario, the model is run to generate the data described by the modeling scenario.
4.1.2. Running the model
Running the DIRSIG model entails providing the model with a configured scenario described in a DIRSIG CFG file. In many cases, this scenario was created using the user interface, but as you will see, the CFG file is a text/ASCII file that can be hand generated or generated by scripting tools if multiple configurations are desired.
The various run-time options for the model are discussed in the DIRSIG3 Run-Time Manual.
4.1.3. An initial tour of the model
A model of this complexity is very difficult to explain in detail to new users from the ground up. Instead, we suggest that new users take an initial tour to see how some basic modeling scenarios are configured and run. The next section contains two tutorials on how to configure and model a framing array sensor and a pushbroom scanning sensor. To keep the presentation at a high-level, not every aspect of the model will be discussed in these tutorials in detail.
Once the user has acquired a general understanding of the model through these high-level tutorials, they can explore the details of each modeling component and the options therein. Detailed explainations of these model components can be explored in In-Depth Material.