VOCALS C-130 Digital Camera Notes

The forward-facing camera is located in the cockpit. It is an AXIS color network
camera. Image resolution is 704 (horizontal) x 480 (vertical) rectangular pixels. Pixel height is 1.1 times the pixel width. Therefore, when displayed on a computer monitor (whose pixels are square) a circular object will appear as an ellipse with an aspect ratio of 1.1. The field of view is about 67 x 53 degrees.

The images were acquired at 1 frame per second and stored as 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 reported to the camera by the aircraft ntp server. The date and time is also stamped onto the images.

The downward-facing camera is located on the bottom of the body of the plane.
It is a Point Grey Research Hi-Res Flea - Color, 1024x768 resolution. The
Navitar DO-412 lens has a focal length of 4 mm. The field of view is about
62 x 48 degrees with some barrel distortion.

Images were acquired once per second and stored as JPEG-compressed files,
roughly 100 kB each. No processing of the images was performed beyond
converting the raw pixel signal into a 24 bit color image. Applying a
sharpening filter as is ordinarily done by consumer digital cameras will
considerably improve the appearance. The UTC date and time are encoded in
the filename as YYMMDD-HHMMSS.jpg.

For the preliminary MPEG-4 movies each image was processed with the linux
ImageMagick toolkit. The image was first cropped to 512x384 pixels.
Sharpening was then performed [SHARPEN(0.0x1.0)]. Where both forward- and
downward-looking camera images are avilable, the images were combined into
a single frame. Each image was then annotated in the lower right with the
time the image was recorded and data values at the image time for a set of
data paramters chosen by RAF. These 1-second annotated images were compiled
into a video stream running at 15 frames/s, 1000 k bps data rate.

The movies can be played by Quicktime 7 or later (Mac and Windows), xine
(linux) and mplayer (multiplatform, not tested).

Flight comments:
RF01: Camera ceased recording images at about 20:58:09
RF07: Only forward-looking camera is available.
RF08: Only forward-looking camera is available.

J. Goldstein
S. Beaton
NCAR/RAF
2009-05-22