Vis5D Movies of VIL Data

Before Viewing

We have an example set of Volume Imaging Lidar images and data available in Vis5D format. Vis5D is a program to view 3D time dependent data sets that runs only on UNIX computers. In order to view the following files, you have to install a Vis5D viewer into your machine from the Vis5D Web site. Then view the Vis5D images directly off from our Web site or from the CD-ROM.

Note for the Netscape users: For easy viewing of the movies, modify your .mime.types to include line:

application/vis5d v5d

and your .mailcap to include line:

application/vis5d; vis5d %s .

Warning: When viewing these files with the web browser, it loads the whole file into a temporary file on your hard disk before starting Vis5D to view it.

Volume Description

The sample data volume has been produced from Volume Imaging Lidar (VIL) cirrus cloud scans. These scans were aligned to be nearly perpendicular to the wind. Consecutive scans enable a reconstruction of the cirrus clouds within a volume when the wind speed and direction are known. The center scan in the volume is not position corrected but the other scans in the volume are shifted by the wind speed and direction to the position at which these clouds were at the time of the center scan. Consecutive volumes are created by choosing a new center scan later in time with the corrections for the other scans in the volume. Each volume is centered on the Lidar site. The reconstructions assume that the cirrus cloud structure does not change during the time it takes the cloud to drift across the volume. External information is needed to calculate the backscatter cross section from the uncalibrated VIL data. Three-dimensional backscatter cross section fields are derived from Volume Imaging Lidar (VIL) using an approximate calibration from simultaneous High Spectral Resolution Lidar (HSRL) data. For more information how these volumes are created, read this link.

These volumes in the data and movie files are in the form of a 10-based logarithmic value of the aerosol backscatter cross section [1/m/sr] with extinction correction at 1064 nm. The extinction cross sections can be derived by dividing the backscatter cross section by the backscatter phase function. The average backscatter phase function measured by the HSRL in cirrus clouds is 0.028 1/sr. Additional information on the VIL and HSRL is available on our Web site on the Internet.

Following image gives a brief description of a Vis5D graphics window.

Sample Volume

A Vis5D data file (size 15 MB) generated from lidar data obtained on September 16, 1995 during Lake Koshkonong field experiment is provided as an example. We have more Vis5D data volumes in our archives. If you are interested in them, contact Ed Eloranta.

UW Lidar // March 29, 1996 // wolf@lidar.ssec.wisc.edu