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Mars rover image wishlist
pgrindrod
post May 19 2016, 08:35 AM
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I couldn’t find this anywhere else, so hopefully this is the right place for this request…

I’m aware of many excellent examples of how people here, and elsewhere, have used images from spacecraft, and in particular from rovers and landers.

But if there was a hypothetical rover on Mars in the near future, taking stereo images on a daily basis, and you could help define how those images are released, what would be on the dream wish list for those images, assuming a similar policy to MER and MSL?

So things like: what image format and processing would be best, the preferred type of website/database serving those images up, what metadata is essential/would be good, and anything else that would be useful.

I have also been trying to collate examples of how these images are used, but it would be good to be directed to any cases that people found to be particularly inventive/impressive/useable. Of course, it might not be possible to predict all the ways that images might be used in the future, but having a list of best practices for sharing these images would be useful.

Many thanks for any input people might have.
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mhoward
post May 24 2016, 08:36 PM
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I’m coming from the point of view of apps, e.g. Midnight Planets.

Basically what I’m looking for is the LBL files. If the same information can be put into JSON format, great. It needs to be easily and efficiently accessible to a bot - i.e., it should be just simple web pages, accessed through well-defined URLs.

When I say accessible to a ’bot’, I mean a single server program, not lots of client programs. I can’t image any scenario in which I would release an app that directly accesses data that I don’t control. What I do is download everything - image data and metadata, wherever I can get it - to my server, re-process and re-package what I need, and host it myself. In addition to hopefully being more polite, this is just basic sanity for me: apps updates are hell, and I can’t risk being put into a situation by a change in a server that isn't mine. (This is not a hypothetical concern. Such changes have happened, and I have dealt with them on the server side.) So, what I need is just the data and metadata. There doesn’t need to be any thought put into formatting the data for a hypothetical large-scale client program; from my point of view, that effort can be counterproductive. I could probably think of real examples of metadata being excluded, images being overcompressed, thumbnail sizes that are useless to me, arbitrary pagination of data, etc., which may have been intended to be helpful, but weren’t, at least not to me. Just the straight data, as much of it as possible, please.

I have no problem with compressed JPGs, as long as they’re not too compressed. (Which has happened.) What I need (and have never had, AFAIK), is the information about how the image was stretched (mapped to 256 grays, or whatever was done to it) - so that process can be undone programmatically, not through guesswork. Also I guess exposure would come into play, unless we were talking about calibrated images, which we probably wouldn't be. It's been a while since I've looked at this stuff, so take this comment with a grain of salt.

One nice thing about JPG files is, some metadata can be included with them. It would NOT make sense to include all the LBL file within the JPG, but it could include the stretching parameters used to map the image to 256 grays, for example. I do exactly that in Midnight Planets for MER-A and MER-B. My server program downloads the calibrated images from the PDS, converts them to high-quality JPGs with embedded EXIF information including the stretch used, and re-hosts them for the client program. The result in the client app is nearly indistinguishable from displaying the source PDS images, in most cases, but uses a fraction of the storage space and bandwidth.

I hope to use the CAHVOR data more in the future. Particularly with the camera specs I’ve heard for a hypothetical Mars rover, seems like it’d be even more necessary for what I'd like to do.

I would prefer to use the image metadata directly, not try to extract pieces of it that have been processed into SPICE data. In fact, hypothetically, if the metadata was only available through SPICE, I would probably not spend the time and effort to extract it, with the experience of MSL behind me. I would just wait for the data to hit the PDS. Which would be a shame; I like live data.

Basic information about the cameras, especially the image filename format, needs to be available. I spent an absurd amount of time trying to ‘guess’ this information for MSL. I will probably never have the time to do that again, even if I thought that was fun. Which it wasn’t.

Another basic point about the filename formats: even for raw web-released products, the filename format should match what will end up in the PDS. Dealing with multiple filename formats for the same MSL image products has been ugly, on this end.

I hope this is helpful in some way.

- Mike
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