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Long term status of Lunar Terminator Visualization Tool?

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#26 Tom Glenn

Tom Glenn

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Posted 22 July 2019 - 03:17 AM

I know this goes back a bit, I still have this from few years back and enjoy using it to id craters. I just have the low res skin and dem. Curious how to add the higher res images into it if anyone knows?  I see some Kaguya images and other really nice hi res stuff in files from the links above. Thanks for any help.

Just in the last few days I've started playing around with LTVT, after much procrastination.  I can basically echo what has been said in many other posts before, in that LTVT is an amazing resource, but one that requires some considerable reading and troubleshooting.  In principle, you can download any number of files to use for the DEM simulations, as long as the format can be read by LTVT.  The best current data to use is LOLA data from the LRO.  This is available in multiple locations, but one I found that is working is through MIT at the following site:

 

http://imbrium.mit.edu/DATA/LOLA_GDR/

 

You first have to decide whether you want cylindrical or polar data.  The polar data has even higher resolutions available.  Whichever you choose, you then need to click on the folder labeled "IMG".  LTVT won't know how to read the other files.  Then, within that folder, only select files that start with "LDEM".  If you try to use any of the files that start with other names, you will get an error.  For any LDEM file you download, you need to download two files, both the .IMG file and the .LBL file.  Place both in the same folder that houses your LTVT program.  

 

You then need to select the appropriate file to use for the DEM through the "Tools" menu and "Change DEM options".  One cautionary note here.  Depending on your system, you may get an error saying that LTVT cannot allocate enough memory.  The LDEM files are very large.  In my case, I'm running Windows on a virtual machine on a Mac, and although my system has 16GB of RAM, I don't think all of it is accessible in the virtual machine, so I was getting errors when trying to use the highest resolution LDEM files.  This is too bad, but I was able to use the file that gives a resolution of 120m/pixel for the polar regions, and about 500m/pixel for cylindrical projections.  The .LBL files can be read in a text editer (you might have to append .txt to the end of the file name) and this will give you specific information about the data, what coordinates it covers, and the resolution.  Some maps have numbers corresponding to meters/pixel in the file name (with an "m" in the name), but others just have a number and this correspond to the number of altitude readings per degree, such that higher numbers have finer resolution.  For example, the LDEM_64.IMG file has 64 readings per degree, which corresponds to about 473m/pixel, which is similar resolution to many high quality images taken from Earth (the highest quality images from Earth can exceed this, down to perhaps 200m/pixel, but for almost any practical purpose, 473m/pixel is pretty good, especially if you are using this as a tool to aid in visual observing rather than imaging).  If your system can handle it, there are higher resolutions available, all the way down to 5m/pixel in the immediate vicinity of the poles.  


Edited by Tom Glenn, 22 July 2019 - 03:23 AM.

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