RICO Logo, 8,273 byte jpg

Project # 2005-135 RICO

Rain In Cumulus over the Ocean

Principal Investigator(s):  Bob Rauber, Harry Ochs, et al.

NSF/NCAR C-130Q Hercules (N130AR)

RAF Logo, 5,367 byte png

Digital Images and MPEG Movies

by Stuart Beaton, July 2005

We have been experimenting with using a digital camera and computer image recording as a possible replacement for the analog-camera/VHS-tape video system currently in place on the C-130. Besides being of higher quality, the digital images can be easily manipulated and imported into documents and, as we have done, made into digital movies which offer instant access to any portion of the flight and lossless reproduction.

For the RICO experiment we have digital camera images from FF02, FF05, and all research flights except for RF01 and RF04. (For these two flights we captured images from the VHS video tapes to substitute for the digital images.) There are some gaps in data, typically a few minutes long. Starting late in RF16, when the sun is in the camera's field of view, the entire image blacks out, probably as a result of sensor saturation. It appears that vibration caused the lens iris to gradually open during the length of the project.

Raw images
The images were acquired at 1 frame per second. They are stored as "high-quality", compressed JPEG files, typically 40kB each. The file name is in the form "c130__fwd_yymmdd_hhmmss.jpg" where "c130" is the platform; "fwd" indicates the forward viewing direction; yymmdd is the 2-digit year, month, and day; and hhmmss is the UTC hours, minutes, and seconds. Each image is annotated with date and time as reported to the camera by the aircraft's ntp server. The images are stored in tar files covering a one-hour period. The tar files are about 200 MB in size.

Movie files
The flight movies are made from the one-frame-per-second images, but they play back at 24 frames per second. Therefore, an entire 10-hour flight is viewable as a 25-minute movie. Playback software often has options for varying the playback speed as well as single-frame step capability, forward and backward. The aircraft position, attitude, and a number of state parameter measurements are included as a sidebar in the movie.

To create the MPEG-4 movie files the raw images were scaled to create square pixels for computer display, and the netCDF data were added to the side to give a standard movie resolution of 720 x 480. These processed image files were then compiled into a QuickTime movie and exported using the 3ivx MPEG-4 codec. The movie file for a flight is about 250 MB in size. Playback of the MPEG-4 file requires Quicktime Player version 6 or later (Macintosh, Windows), or mplayer or VLC (Linux, Macintosh, Windows and others). "Quicktime" is available at no charge from Apple Computer, "mplayer" from MPlayerhq.hu, and "VLC" from videolan.org.

Digital camera information
Digital images were acquired from a forward-facing cockpit camera. The field of view is 67 degrees horizontal by 53 degrees vertical. Raw image resolution is 704 (horizontal) x 480 (vertical) rectangular pixels. Pixel height is 1.1 times the pixel width. When displayed on a computer monitor, a square will appear as a rectangle with an aspect ratio of 1.1.

Analog camera information
The analog camera used for the VHS recording, from which the RF01 and RF04 images were captured, has a field of view of 55 degrees horizontal by 40 degrees vertical. The capture resolution was 640 x 480 square pixels. In addition, the digital and analog cameras are pointing in slightly different directions.

For RF01, the video was annotated and scaled as described above for the digital images. For RF04, the video was compiled from the captured images with no processing and is 640 x 480 pixels. Hence the pixels in RF01 and RF04 have different angular sizes, which also differ from those in the digital camera movies.

Last update: Tue Aug 2 17:47:20 MDT 2005