Map projected CTX images ?, How to merge/overlay CTX with map projected HiRISE Options

[Nirgal]

Does anyone know if/where there are map projected CTX images avilable ?

There are the EDR (i.e. raw) data sets as IMGs at PDS, but so far there seem no RDRs (i.e. calibrated and map projected) versions of the CTX images publicly available (yet?)

However, when I'm looking at the tight CTX image integration in Google Mars it seems that they have the exact footprint data of all CTX images readily to be overlayed with the global Mars/MOLA/HRSC map ...

So somehow the map projection of CTX images/footprints must have been done at least for Google Mars.

Ross Beyer even has a link on his web page to the footprint data of all CTX images as KML files:
http://pirlwww.lpl.arizona.edu/~rbeyer/kml/CTX_PDS.kml

So I'm courious, if the complete map projected CTX image data exists somewhere or if it is required to do the projection for each image oneself with the usual ISIS tool chain only ?

Background: what I really want to do is to merge/overlay map projected HiRISE images with their corresponding CTX observation as a kind of "background"-layer ... Ideally this should be performed with pixel-precision which, of course, requires exact map projection from one
camera's space to the other.

Probably this must have been done before, but I couldn't find enough information on this in the ISIS doc & ISIS/GIS community forums.

Thanks in advance for any help !

Bernhard

[djellison]

It's fairly easy - just follow this from end to end :
http://isis.astrogeology.usgs.gov/IsisWork...rbiter_CTX_Data

[Nirgal]

ok thank you Emily, Doug !

So it is definitely going to involve ISIS, as I have already suspected.

As far as the radiometric calibration is concerned I wrote my own C++ program some time ago using the source code in the ISIS program "ctxcal" as a reference -> that produced reasonable results converting the IMGs to calibrated 16 Bit Tiff/PNG.

However things are not so easy with map projection (without the SPICE kernels and such

So in the mean time I am in the process of downloading the whole ISIS installation (30+ Gigs ) to be run in a Linux VM....

The following quotes I found from the ISIS support forum might also be helpful:

CTX images are only released in raw PDS format. They have not been map projected which means they are not ready for a GIS or mapping application. All PDS raw (EDR) images must first be preocessed before they should be used. Some teams like HiRISE, MOLA, THEMIS, HRSC, CRISM, because their images are hard to work with or they are just being nice, release map projected images or mosaics as well as their PDS EDRs. These derived products, which again are map projected, can be run through pds2world.

The bottom line is that you will need to run these images through ISIS3 (or other app) to calibrate and push into a map projection.

Here is a CTX helper script that you can use once you have ISIS3 installed:
http://isis.astrogeology.usgs.gov/IsisSupp...opic.php?t=1393

I imagine Doug will reply before long with tales of the pain he has gone through to reproject the CTX images

It's fairly easy - just follow this from end to end :
http://isis.astrogeology.usgs.gov/IsisWork...rbiter_CTX_Data

@Doug: ok, so were you actually successful with projecting and stitching HiRISE and CTX together in the same image space ?

[djellison]

@Doug: ok, so were you actually successful with projecting and stitching HiRISE and CTX together in the same image space ?

Not done that - I'm not clever enough - I would simply use photoshop to lay HiRISE over CTX