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On 09/29/2010 06:12 PM, Mario Julio Barragan Arce wrote:
<blockquote
cite="mid:AANLkTimM1E6dMYuSt6KmdprgSZ9tp24f=Lr+P9ffLiiB@mail.gmail.com"
type="cite">
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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 </blockquote>
<br>
Welcome, and good decision.<br>
<blockquote
cite="mid:AANLkTimM1E6dMYuSt6KmdprgSZ9tp24f=Lr+P9ffLiiB@mail.gmail.com"
type="cite">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 dataset?<br>
<br>
In particular, there is a landcover raster image in Erdas "img" format
(prgap_landcover.img) that I would like to import from here:<br>
<br>
<a moz-do-not-send="true"
href="ftp://ftp.gap.uidaho.edu/products/Puerto_Rico/GISdata/Landcover/1_Land_cover_grid/">ftp://ftp.gap.uidaho.edu/products/Puerto_Rico/GISdata/Landcover/1_Land_cover_grid/</a><br>
<br>
(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)?<br>
<br>
</blockquote>
If the file is somewhere on your computer, then just enter the path to
it with the 'input=' parameter to r.in.gdal. Something like:<br>
r.in.gdal in=/path/to/prgap_landcover.img out=prgap_landcover <br>
<br>
(BTW, I think you can actually even import into GRASS straight from the
URL...)<br>
<br>
<blockquote
cite="mid:AANLkTimM1E6dMYuSt6KmdprgSZ9tp24f=Lr+P9ffLiiB@mail.gmail.com"
type="cite">(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<tt>.</tt><br>
<br>
(3) When do I create the location for my data? Do I do this before
anything else?<br>
</blockquote>
<br>
YES, before anything else. This step is crucial, and sometimes confuses
new users. You *must* have a correct LOCATION defined at the start such
that it matches the CRS of the original data. GRASS always insists that
all maps in a LOCATION are projected in exactly the same CRS.<br>
>From the metadata below it looks like this file is projected in the LCC
projection matching the EPSG code of 2866. That's NAD83(HARN) Puerto
Rico and Virgin Islands.<br>
You might try to first use the wizard to create a new location based on
this EPSG code. That insures all the parameters get entered properly.
Then, after starting GRASS in this location (also create a MAPSET - the
GRASS way to keep maps filed in some directory which is logical for
your work), try the r.in.gdal command.<br>
<br>
<blockquote
cite="mid:AANLkTimM1E6dMYuSt6KmdprgSZ9tp24f=Lr+P9ffLiiB@mail.gmail.com"
type="cite"><br>
(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. <br>
<br>
Any suggestions will be very welcome. Thank you in advance. Saludos,
Julio.<br>
<br>
</blockquote>
Cheers. For future questions, let us know your OS and version of GRASS.
And posting the output of commands like g.region -p, v.info, r.info
will often help.<br>
<br>
Regards,<br>
Micha<br>
<blockquote
cite="mid:AANLkTimM1E6dMYuSt6KmdprgSZ9tp24f=Lr+P9ffLiiB@mail.gmail.com"
type="cite">
<pre>Spatial_Reference_Information:
Horizontal_Coordinate_System_Definition:
Planar:
Map_Projection:
Map_Projection_Name: Lambert Conformal Conic
Lambert_Conformal_Conic:
Standard_Parallel: 18.033333
Standard_Parallel: 18.433333
Longitude_of_Central_Meridian: -66.433333
Latitude_of_Projection_Origin: 17.833333
False_Easting: 200000.000000
False_Northing: 200000.000000
Planar_Coordinate_Information:
Planar_Coordinate_Encoding_Method: row and column
Coordinate_Representation:
Abscissa_Resolution: 15
Ordinate_Resolution: 15
Planar_Distance_Units: meters
Geodetic_Model:
Horizontal_Datum_Name: North American Datum of 1983
Ellipsoid_Name: Geodetic Reference System 80
Semi-major_Axis: 6378137.000000
Denominator_of_Flattening_Ratio: 298.257222
</pre>
<br>
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</blockquote>
<br>
<br>
<pre class="moz-signature" cols="72">--
Micha Silver
Arava Development Co. +972-52-3665918
<a class="moz-txt-link-freetext" href="http://surfaces.co.il">http://surfaces.co.il</a>
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