This is a polar projectiong


and after Phil's excellent guidence, I've figured out how to do those. They're great for a sense of 'place' and cross referencing horizon features with maps or orbital imagery.

However - if you want to generate your own map like material, you need more of a vertical projection thus...


Now - I have no idea how to do that Part of me thinks it could be fuged by stretching away at a polar projection, but is there a more obvious way using the 'ordinary' tools?

Doug

(images from http://marsrovers.jpl.nasa.gov/gallery/pre.../20051021a.html )

Dilo makes vertical projections using Povray (I think). I have used a rubber-sheeting technique (georeferencing in a GIS) to go from polar to a map.

There is a way to fudge it using Photoshop or similar software. Take the original pan, say 4000 by 400 pixels. use image-size to make 3000 by 6000 pixels - 6000 high. select all below 1500 pixels (using the ruler as a guide, set to pixels) and with edit-transform-scale shrink it about 10 or 15 % (bottom towards top). Then select all below 1700 pixels and do the same. Then select all below 1900 and do the same and so on. Crop it to 3000 by 3000, rotate 180 and do the polar coordinates transformation.

What you get is the original pan with its foreground greatly compressed and the outer parts stretched radially away from the centre... which approximates a map view. This is what I'm doing here. It's not an accurate map but a quick approximation to one, and I can then go on to rubber-sheet the result to a better geometry if I need to.

Phil

Let me take this chance to ask if somebody knows about freeware to make polar projections?

GIMP might do it?

Doug

I think GMT can do this, but be warned that the learning curve is very steep.

http://www.soest.hawaii.edu/gmt/

As far as I can tell, the NASA map projections seem to do a simple geometric projection of the image onto a horizontal plane. (something like a stereographic projection). This means that rocks and other objects extending vertically above the surface are stretched out radially as in this example.

Is anyone (amateur or in the profession) doing projections which accurately portray distances, perhaps by draping the imagery onto a three dimensional model of the local surface derived from the stereo distance measurements.

Steve (sorry for putting the large image in-line; I know there's a way somewhere to put in a thumbnail. )

The terrain models are there in the PDS for released data - but I don't know any way in which to use them, they're not in a format that can be dropped into any animation package I know of. If I could do that, then I would do it in a MOMENT ( I did it with MPF last year )

Doug

The lack of useable meshes in the PDS is a big disapointment. They've made available two different mesh products (ViSTa and Performer Binary) both of which look like they are useable by specific NASA software (SAP and RSVP respectively). I know it might seem extraneous for them to archive a generic format that isn't used inside JPL or NASA itself, but it sure would make it easy (nay, possible) for anyone else to make use of the mesh data.

(this is when someone jumps in saying "oh, i've got a conversion program from ViSTA->3DS"...right?

I wish I could say I have such a beast but I don't. However how hard would it be to do? Are the specifications for both standards available? If so then surely it's just a matter of getting the right programming whiz to see this as a cool project.

I'm a historian by trade and as such I'm concerned with the stability of archives. Good practice demands that you archive data in a format that's not proprietary and is so widely used that it's still likely to be readable twenty years from now. From that perspective it is irresponsible to archive material in a format that requires in-house software.

Steve

I believe the Performer Binary files ( FFL designation, .pfb extension and can be found on the PDS Imaging node) might be readable in other software. I'm just not familar enough with the standards to do anything with it personally.

Also, it looks as if the PFB files correspond to the entire site, not just a single stereo pair. If this is the case, I'm not sure if they include their own textures (or does each PFB correspond to a mosaic?). The ViSTa files represent just one stereo pair, so it wouldn't be too hard to drape a single color image over its corresponding mesh.