Hi everybody,

 

Can anybody please tell me where I can find global Mars data on longtitude, lattitude and elevation. Just a txt file, not all sorts of mumbo jumbo interactive maps and such. I have been looking for it but this site is the pits and other sites don't help you out any further either. It would be a great help. Thanks in advance,

 

Roel Knol,

Netherlands.

The most recent global altimetry data for Mars is from the Mars Orbiter Laser Altimeter (MOLA) on Mars Global Surveyor. The global data products are the MEGDRs (Mission Experiment Gridded Data Records), which are image maps of topography, planetary radius, areoid, and counts, available here: http://pds-geosciences.wustl.edu/missions/mgs/megdr.html.

 

For higher-resolution coverage of a selected area of the planet, try the MOLA PEDR Query Tool, which is part of the Mars Orbital Data Explorer service. This tool can provide topography data as an image or as an ASCII table. It is available here: http://ode.rsl.wustl.edu/mars/indextools.aspx?displaypage=molapedr. This tool is useful for small areas. It would not be practical to request output for the whole planet because the resolution is so high. 

The MEGDRs in the link you gave are in a .img format. What is the easiest way to convert these .img files into simple text files that have lat, lon, elevation in the columns?

The MOLA PEDR Query Tool I mentioned before will allow you to create output as an ASCII text file.

The query tool you mentioned is for PEDRs, I'd like to look at the globally gridded MEGDR products.  

When I use the ODE data product search (as suggested at the top of the PEDR Query Tool 2 page), I can bring up a file, for example MEGT90N180GB.IMG, however, the PDS product files and Derived files do not include a simple text table (lat, lon, elevation), it only includes more images and some shapefiles. 

What is the easiest way to convert the MEGDR products to a simple text table?

 

I asked the ODE developer if she could suggest a way to do this. Here's her answer. She reads this forum too.

Hi Susie,

Below link shows an example on how to read those MEGDR products  with Matlab. The user could modify the code a little bit to output a table with lat, lon, and height.

https://www.mathworks.com/matlabcentral/fileexchange/13444-using-data-from-mola?focused=6780621&tab=example&requestedDomain=www.mathworks.com

Another way is to convert the PDS IMG to ERDAS IMG in ArcGIS. Then use ERDAS to convert the ERDAS IMG to an ASCII table with lat, lon, and height.

Both Matlab and ERDAS are commercial software. Otherwise, the user needs to write his own program to read the PDS IMG data. The label includes everything that the user needs to know to read the data file.

Please let me know if the user needs further help. Thanks,

June