Dealing with artifacts in Wilbur

[acrosome]

That's the data, yes. Those are the original GTDR data files I mentioned. (As I'm sure you know, you were in the mercator directory, but sinusoidal and two polar projections are avaialble in a higher directory.)

I suspect that these streak artifacts are in this data too, since my file is just one large stitched-together image of the same data. I stumbled upon a site that would export them as one large jpeg in cylindrical projection for me. That's where I got mine, since cylindrical is more useful, being able to load into G.Projector and all. (I am far too ignorant to manipulate those files into an equirectangular cylindrical projection on my own. And I'm also not sure how to change the CD images into a useful file format.)

USGS Map-A-Planet

This was the website I used to order the jpeg. You have to dig around a bit to figure out how to order it at the resolution and in the projection that you want. The original GTDS data is about 4.6km/px, so that's what I ordered. It takes them about a day to put the jpeg together for you and email the download link (which is only good for a few days).

I also took a closer look at my stitched-together cylindrical image in Wilbur last night, and there are many more subtle north-south streaks all over the place. I think I have a lot of work ahead of me.



EDIT--- I just re-ordered another version from Map-A-Planet, this time in 16-bit TIFF rather than 8-bit JPG to hopefully get more detail in elevations. (See how much I've learned already?) When I get the link I'll post it here for others to download.



EDIT AGAIN-- Well, you got me thinking about this again, so I was poking around the ISIS forums and found this:

ftp://pdsimage2.wr.usgs.gov/pub/pigp...ar_properties/

It looks like there is some sort of topo data in that directory, too, but it is again beyond me. What's frustrating is that I suspect that cleaning up this data and producing a decent image at that resolution would be trivial for some of these astrogeology guys, but I'm struggling. But then, I guess I don't have their resources, eh?

There is also something called the RDRS spherical harmonic topography model available:

http://pds.nasa.gov/ds-view/pds/view...5-TOPO-L2-V1.0

http://pds-geosciences.wustl.edu/mgn...l2-v1/mg_5201/

From the description in the first link this might actually be nice data, but I just can't figure it out. And I have no idea what the resolution is, projections, file formats, etc. But the filesizes are quite small, so I suspect that the resolution is poor, and I moved on.

[acrosome]

Wow, that was fast. Here's the link to download that TIFF I just ordered:

Planetary Data System - Map-a-Planet

Warning: it is 54.1MB, and the link is only good through May 4th. But it looks like it preserves the elevation data that was lost on my last attempt- no plateaus on all the higher mountaintops. Still has the streaks, though. I'll look at it in Wilbur when I get home.

EDIT--- Huh. Wilbur doesn't read TIFFs. I have to convert it into a PNG, and I do that in GIMP, which can only handle 8 bits, so I lose some data anyway. The contours look very pixelated. I'll start hand-correcting what I have, unless Redrobes manages to produce a miracle for me...

[acrosome]

For anyone who cares- it is a heck of a lot easier to patch blank spots in the data with the clone tool in GIMP than in Wilbur. Once I get this done I'll work on the streaks, which I suspect will be the opposite- easier to manipulate in Wilbur.

Say, what's the difference between simple cylindrical and equirectangular cylindrical? My google-fu is failing me. Near as I can tell they are the same, but my simpe cylindrical images seem to lack the poles. I'm not sure if this is a characteristic of the projection or if the data is simply missing. I've certainly seen maps made using the same data that don't have such large holes, but they may have filled some in with Venera or Pioneer data or something.

[Redrobes]

Before I do anything I can I check the link. Did you order it using something like this:

Map-a-planet

and get the email link through for download ?

[acrosome]

Yes, that's the website I ordered it from. They then send you a link for download. (But the link I posted above to download the file has expired- we'd have to order a new one.)

Alternately, what's a decent filesharing schema and I'll post it- though I've never done that before. Or I could email it to you. (If you trust me.)

I've been working on patching the blank spots in the data, and I played with the contrast and brightness so that the map uses the full 255 grayscale colors. It's starting to look useable. I still haven't started working on the streaks, though. If you can easily correct them then you're a better man than I. I'll probably start fiddling with them by hand next.

On that note, in Wilbur is there a way to select a region and drop it by a defined amount? For instance, so that every point has it's altitude is lowered by X?