Jim Bell Q'n'a, Questions Please |
Jim Bell Q'n'a, Questions Please |
Jan 22 2006, 11:06 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
Jim Bell's agreed to do a brief Q'n'A in a few days time, so similar to the one I did for Steve, I want your questions! Try and keep it quite 'current' if you can, as we're going to make this more a 'news' outlet than a look back type chat.
We're going to try, if this one works, to do these every couple of weeks or so, a bit of Rover news and a bit of Q'n'A each time, but we'll see how this one goes first! Fire away people If they're all crap, don't worry, I've got LOADS in mind. Doug |
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Mar 22 2006, 05:58 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
You've lost me. The very best data is the RAD .img files as far as I know - what is it you're actually after instead of that?
Doug |
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Mar 22 2006, 07:34 PM
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Member Group: Members Posts: 656 Joined: 20-April 05 From: League City, Texas Member No.: 285 |
You've lost me. The very best data is the RAD .img files as far as I know - what is it you're actually after instead of that? Doug Fundamentally I'm after the best possible quality images in an international standard format. If the image is lossless, that would mean either PNG or Jpeg2000 (which has a lossless mode), though I'd settle for Tiff or Bmp (and happily convert to one of the others). If the image is compressed (most are), then wavelet compression yields the best quality with fewest artifacts (and is what they use on MER), and Jpeg2000 is the standard format. Admittedly Jpeg2000 involves additional processing overhead, but when dealing with limited bandwidth they seem the optimum solution. There are just all sorts of benefits to wavelet-compressed images, completely aside from file size. Upon display they yield minimal artifacts, scale smoothly, and you can even pull an arbitrary resolution thumbnail out of one without having to read the entire file. Aside from that, there are a slew of papers out there on such topics as pattern recognition and texture analysis simply based upon the wavelet coeficients (similar things are possible with Jpeg images). I'm happy that they're using wavelet compression to begin with, I'm concerned that by choosing a non-standard format they have to some extent isolated the potential data analysis to within the JPL community. My understanding of the .img file structure is that it contains a lot of useful header data plus a tag specifying the raw format of the image data, and then the actual image data is in the originally acquired format. For instance, the Hughens probe sent back Jpegs, so within the corresponding .img files there should be that raw Jpeg data, and likewise for the MER images in terms of the ICER format. Anyway, I see that you've already done the interview and I look forward to hearing what he had to say |
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Mar 22 2006, 07:42 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
My understanding of the .img file structure is that it contains a lot of useful header data plus a tag specifying the raw format of the image data, and then the actual image data is in the originally acquired format. For instance, the Hughens probe sent back Jpegs, so within the corresponding .img files there should be that raw Jpeg data, and likewise for the MER images in terms of the ICER format. That's not my understanding of it - I think the imagery data within an IMG is totally uncompressed (thus every full frame IMG is always 2mb. If they were in any way compressed, they would vary) Doug |
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Mar 22 2006, 08:50 PM
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#5
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Dublin Correspondent Group: Admin Posts: 1799 Joined: 28-March 05 From: Celbridge, Ireland Member No.: 220 |
That's not my understanding of it - I think the imagery data within an IMG is totally uncompressed (thus every full frame IMG is always 2mb. If they were in any way compressed, they would vary) But some of them are rebuilt from an original that was compressed, right? like the 1bpp, 4bpp etc images? |
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