Example files and demonstrations of the LIDAR capabilities can be found on the DIRSIG website in the "Demonstrations" directory: http://www.dirsig.org/demos
The DIRSIG LIDAR/LADAR model produces focal plane arriving photon counts within user-defined time gate. The time gate description includes the minimum and maximum time after each pulse that the photon counts will be recorded, and a delta time resolution within that window. However, the common LIDAR/LADAR product that most people are familiar with is 3D point cloud data. To create this type of data set, this photon arrival data cube needs to be processed by a detection model and processed by a geolocation algorithm to translate these photon counts into a 3D point cloud that is the common product from such a system.
It is expected that most users will take the raw photon arrival cubes and process them through their own complex detection algorithm, time-of-flight calculation, and geolocation algorithm. These tools can process the raw photon arrival cubes directly by consulting the output file description in the "LidarCaptureMethod" documentation: http://www.dirsig.org/docs/CDLidarCaptureMethod.pdf
For those users who are not going to write their own tools to create these 3D data sets, the DIRSIG model is distributed with a simple detection and geolocation tool to perform this conversion. This tool is designed to emulate an avalanche photo-detector (APD) style focal plane, and the "detection" model is a simple threshold. A more elaborate statistical detection model may be added in the future. The tool will compute a single range for each pixel, for each pulse once the photon arrival count has reached the user-supplied threshold. As a result, the generated point cloud file has a single return per-pixel, per-pulse. Multiple returns are more common in linear-mode detector systems that digitize the arriving flux as a function of time and then post-process the flux shape to extract various returns.
This command line tool takes the name of the input photon arrival data cube file (generated by the "lidar" capture method), a threshold that will be used to trigger the time-of-flight measurement and the name of an ASCII, XYZ output point cloud file.
The command line syntax of this tool is shown below:
prompt> fxyx_convertor
DIRSIG: LIDAR FXYZ Conversion Tool
Version 4.0.5
Build Date: Jan 26 2006 18:13:21
usage: fxyz_convertor --threshold=<value> --input_file=<filename> --output_file=<filename>
The C++ source code for this tool is also available for download if the user wishes to take this simplistic tool and expand it to implement a more elaborate detection process. The source code also serves as a developer's guide to parsing the DIRSIG photon flux cubes created by the LIDAR model. The code is available on the DIRSIG website in the "Documentation" section: http://www.dirsig.org/docs