Sun, 10 Oct 2004

Mount St. Helens meets Linux

The Mount St. Helens VolcanoCam is a webcam located at the Johnston Ridge Observatory. The online image is updated approximately every 5 minutes. With recent volcanic activity, I started checking the VolcanoCam image periodically.

Not having time, patience, or inclination to watch it for the hours on end that would be required to see an eruption which could occur at any time, I ran a small script to begin grabbing the image every 5 minutes.

Actually, to call it a script is an overstatement. I simply started a screen session and entered on the command line:

 while true; do wget \
 http://www.fs.fed.us/gpnf/volcanocams/msh/images/mshvolcanocam.jpg;\
 sleep 300; done

Originally, I intended to simply let wget run in the screen session for the day and view the images when I returned home. But it's been running continuously since Monday, October 4th, when I started it.

Frustrated with my inability to view the images in a reasonable way, I decided to try to create an MPEG movie with them so I could quickly scan the day's images for interesting events and single step the frames when I found one.

It took a bit of research to discover the tool I needed was ppmtompeg, which is part of the netpbm package of graphics software. It took a bit longer to learn how to use it. The result has been MPEG files for each day starting with Monday, October 4, each about 2MB. I'm using the EXHAUSTIVE search algorithms for best compression, so it takes about 7 minutes to create each MPEG file on my 2GHz P4 system.

I've used the contact form on the VolcanoCam to request permission to share the MPEG files I've created since I don't own the images used to create them. No response, yet. If they grant permission, I'll find a way to get the MPEGs posted on provide links to them.

This little project demonstrates one of the many reasons I love Linux. The tools I needed for this simple, personal use project were readily available and the only cost was the time and effort required to learn them.

[/linux] [link]

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