[Qgis-user] QGIS won't open Martian .img files

[Lester Anderson]

On 8 July 2016 at 14:13, Nicolas Cadieux <nicolas.cadieux at archeotec.ca> wrote:
> Hi,
>
> Qgis uses gdal library to deal with rasters.  I found some information in
> the link below.  Perhaps the gdal user group could help.  It is possible
> that you need an extra driver to read the files. (Perhaps installable via
> the osgeo4w Qgis installer).  You can also try the semi automatic
> classification plugin that is use for remote sensing imagery.  Perhaps there
> is something in that plugin that could help.
>
> http://www.gdal.org/frmt_pds.html
>
> Nicolas
>
> On Jul 8, 2016 08:25, "Adam Neather [via OSGeo.org]" <[hidden email]> wrote:
>
> Hello everyone,
>
> I'm trying to use QGIS to get topographic profiles from Mars Global
> Surveyor data. (Example link below.) While QGIS will open the .lbl files
> as a raster with no problem, I always get the error "Unsupported Data
> Source: /Users/username/Desktop/megr00n180hb.img is not a supported
> raster data source" when trying to open the .img. (In fact, this is only
> under Windows 10; QGIS on Mac OS X refuses to open the .lbl files, too,
> with the same error message.)
>
> The .img files included with the sample data for the tutorials loads
> fine, so I'm not sure what it is I'm doing wrong.
>
> A colleague has suggested it may be because I need a plug-in to be able
> to read NASA's Planetary Data System file format, but I can't find
> anything about that in the official plug-in repository or when searching
> online.
>
> Weird thing is, I'm returning to a project from a few years ago, and we
> used QGIS back then to work with this data set, so I'm as confused as
> it's possible to get!
>
> Any help greatly appreciated,
>
> http://pds-geosciences.wustl.edu/mgs/mgs-m-mola-5-megdr-l3-v1/mgsl_300x/meg004/
>
> --
> -
>
> Adam Neather

If you have access to GMT it is fairly straightforward.

So if you had say the gravity anomaly data, the GMT command (windows
commad window):

GMT parameters to grid 2016 Mars gravity grids:
http://pds-geosciences.wustl.edu/mro/mro-m-rss-5-sdp-v1/mrors_1xxx/data/rsdmap/

xyz2grd ggmro_120_anom_100.img -GGGM-3_anom.grd -R0/360/-90/90
-I5760+/2880+ -ZTLd -V
Note: the Increment -I setting is set to use the exact node dimensions
(with the +)

I think the data gives you the exact size of the raster and the coordinates.

To get this into QGIS you could convert (from GMT) to .asc or Surfer .grd

eg grdconvert grav.grd grav.asc=ef

or grdconvert grav.grd grav_surfer.grd=sf

These data formats are the ones I use most for rasters in QGIS.

Hope this helps.

Lester