[OSGeo-Discuss] First time GRASS user -- how to import an img dataset?
Mario Julio Barragan Arce
mariojulio.barragan at upr.edu
Wed Sep 29 08:11:49 PDT 2010
Hello. I need to learn how to use GIS and I have chosen to do it with GRASS.
My plan is to learn GIS/GRASS essentials during the next 12 months and start
applying it for my research the 12 months after that. I have started reading
the documentation available and playing with the sample data set. However, I
would also like to start playing with a dataset for Puerto Rico (PR) and I
am having problems to import it. How would I go about importing a new
In particular, there is a landcover raster image in Erdas "img" format
(prgap_landcover.img) that I would like to import from here:
(1) What do I do with this img file? Do I first copy and paste it to my GIS
Data Directory? If not, how do I go about telling GRASS where this file is
(if I want to import it)?
(2) I read about the commands to import raster Erdas/IMG files to GRASS
(r.in.gdal -e in=<image.img> out=<image>). If I want to use this command,
should my img file be in the GIS Data Directory first as I suggested in (1)?
Where do I type this command? The GRASS Command Line window seems to open
for an existing Location.
(3) When do I create the location for my data? Do I do this before anything
(4) When trying to create a location from the Location Wizard, I chose as
the method "Select coordinate system parameters from a list". I did this
because there is another file in the above mentioned ftp folder with several
parameters which seem to me the kind of information that the wizard asks
(see an excerpt below). From there I chose "lcc" as the projection code.
However, from here onwards I start having problems. For instance, I don't
know whether to choose "Datum with associated ellipsoid" or "Ellipsoid
only". Also, the wizard asks me "Central Parallel", "First Standard
Parallel", "Second Standard Parallel", and I don't know how that relates to
the two "Standard_Parallel" parameters given below and where do I get the
other "Parallel" parameter from? I seem to be missing one. For the geodetic
datum I think I have to choose "nad83" and I think I will choose "No
transformation" at the end of the wizard.
Any suggestions will be very welcome. Thank you in advance. Saludos, Julio.
Map_Projection_Name: Lambert Conformal Conic
Planar_Coordinate_Encoding_Method: row and column
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
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