[GRASS-user] Converting txt file into raster layer

GRASS GRASS user
1

Good afternoon. A client of mine has given me a large text file (1.6Gig) that he wants visualized in GRASS. In the file, there are 7 columns (Time, Grid Cell Number, Elevation, Thickness, Topography height, U of water velocity, V of water velocity). I’ve never taken something in text form and put it into GRASS. Any suggestions on how to start? My first thought was to convert to netcdf import from there (since I have some experience working with netcdf in GRASS). Is there a more straight-forward way to do this? I have the projection information in a separate shapefile in order to geolocate.

Any help would be greatly appreciated.

Thanks!
Katie

2

I'd go with v.in.ascii or r.in.xyz but, for both, you will need to
know the coordinates of each grid cell.

Another thing to look for is, if you have more than one observation
per time, you might have to separate the file and create one map (or
layer) for each time step. That's something easily done with NetCDF
and programs like GrADS....

Cheers
Daniel

On Wed, Dec 2, 2009 at 5:29 PM, Carbonari, Katie (IS)
<Katie.Carbonari@ngc.com> wrote:

Good afternoon. A client of mine has given me a large text file (1.6Gig)
that he wants visualized in GRASS. In the file, there are 7 columns (Time,
Grid Cell Number, Elevation, Thickness, Topography height, U of water
velocity, V of water velocity). I've never taken something in text form and
put it into GRASS. Any suggestions on how to start? My first thought was to
convert to netcdf import from there (since I have some experience working
with netcdf in GRASS). Is there a more straight-forward way to do this? I
have the projection information in a separate shapefile in order to
geolocate.

Any help would be greatly appreciated.

Thanks!
Katie

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3

Thanks for the help Daniel. I did break up my very large file into lots of smaller files (each of the 5 variables are in 142 different files, one per time step, so now each file has just one time step and one variable in it). The grid is irregular and I have a shapefile that I have read into GRASS with no problem. Each cell in the shapefile corresponds to a line in my new txt files. (Ex, Elevation_00.txt has 228,000 lines, with each line having the elevation corresponding the cell number (line 3 is for cell number 3), where the cell numbers are defined by a shapefile).

What I’m confused about is how to “marry” the 2 together? How do I let GRASS know that I want my text file data put on the same grid as my shapefile data? Has anyone attempted to do this? Any help would be great.

Thanks for all your help so far!
Katie

-----Original Message-----
From: Daniel Victoria [mailto:daniel.victoria@gmail.com]
Sent: Wed 12/2/2009 6:26 PM
To: Carbonari, Katie (IS)
Cc: grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] Converting txt file into raster layer

I’d go with v.in.ascii or r.in.xyz but, for both, you will need to
know the coordinates of each grid cell.

Another thing to look for is, if you have more than one observation
per time, you might have to separate the file and create one map (or
layer) for each time step. That’s something easily done with NetCDF
and programs like GrADS…

Cheers
Daniel

On Wed, Dec 2, 2009 at 5:29 PM, Carbonari, Katie (IS)
Katie.Carbonari@ngc.com wrote:

Good afternoon. A client of mine has given me a large text file (1.6Gig)
that he wants visualized in GRASS. In the file, there are 7 columns (Time,
Grid Cell Number, Elevation, Thickness, Topography height, U of water
velocity, V of water velocity). I’ve never taken something in text form and
put it into GRASS. Any suggestions on how to start? My first thought was to
convert to netcdf import from there (since I have some experience working
with netcdf in GRASS). Is there a more straight-forward way to do this? I
have the projection information in a separate shapefile in order to
geolocate.

Any help would be greatly appreciated.

Thanks!
Katie

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grass-user@lists.osgeo.org
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4

Katie,

One way to solve this would be to link an attribute column from the
shape-file a column in the text file. You will have to use the vector
database tools in grass for that. From there, if you prefer to work
with rasters, you can interpolate the values from the linked shape
file...

Daniel

On Fri, Dec 4, 2009 at 4:51 PM, Carbonari, Katie (IS)
<Katie.Carbonari@ngc.com> wrote:

Thanks for the help Daniel. I did break up my very large file into lots of
smaller files (each of the 5 variables are in 142 different files, one per
time step, so now each file has just one time step and one variable in it).
The grid is irregular and I have a shapefile that I have read into GRASS
with no problem. Each cell in the shapefile corresponds to a line in my new
txt files. (Ex, Elevation_00.txt has 228,000 lines, with each line having
the elevation corresponding the cell number (line 3 is for cell number 3),
where the cell numbers are defined by a shapefile).

What I'm confused about is how to "marry" the 2 together? How do I let GRASS
know that I want my text file data put on the same grid as my shapefile
data? Has anyone attempted to do this? Any help would be great.

Thanks for all your help so far!
Katie

-----Original Message-----
From: Daniel Victoria [mailto:daniel.victoria@gmail.com]
Sent: Wed 12/2/2009 6:26 PM
To: Carbonari, Katie (IS)
Cc: grass-user@lists.osgeo.org
Subject: Re: [GRASS-user] Converting txt file into raster layer

I'd go with v.in.ascii or r.in.xyz but, for both, you will need to
know the coordinates of each grid cell.

Another thing to look for is, if you have more than one observation
per time, you might have to separate the file and create one map (or
layer) for each time step. That's something easily done with NetCDF
and programs like GrADS....

Cheers
Daniel

On Wed, Dec 2, 2009 at 5:29 PM, Carbonari, Katie (IS)
<Katie.Carbonari@ngc.com> wrote:

Good afternoon. A client of mine has given me a large text file (1.6Gig)
that he wants visualized in GRASS. In the file, there are 7 columns (Time,
Grid Cell Number, Elevation, Thickness, Topography height, U of water
velocity, V of water velocity). I've never taken something in text form
and
put it into GRASS. Any suggestions on how to start? My first thought was
to
convert to netcdf import from there (since I have some experience working
with netcdf in GRASS). Is there a more straight-forward way to do this? I
have the projection information in a separate shapefile in order to
geolocate.

Any help would be greatly appreciated.

Thanks!
Katie

_______________________________________________
grass-user mailing list
grass-user@lists.osgeo.org
http://lists.osgeo.org/mailman/listinfo/grass-user