Help with conversion from NetCDF to ASCII

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Does it have to be that ascii format? There are much better options
for regular grids, such as GeoTIFF - but it depends on your target of
course. Note that some software supports different dx/dy sizes, namely
GDAL and Golden Surfer for this format:

http://www.gdal.org/frmt_various.html#AAIGrid

If it does need to be ESRI ASCII, you could write it out with square
cells and then reset the cell sizes in the target (if possible).

Is the requirement for square cells with the ESRI version of this
format, or with the software you want to use next?

As a last resort you could resample the grid using R's indexing/seq
functions, or with spsample in package sp, or warp it with an external
tool like gdalwarp.

Cheers, Mike.
Hi All,

I want to convert netCDF files to ESRI ASCII grid. I used the package ncdf
to read the file and get the required variable in the matrix format. Now I
want to write this matrix into ESRI ASCII grid. Looking at the extends of
the data, and the row and column dimensions, I know that the CELLSIZE is not
square.

Is there any way, I can convert this data into square ASCII Grid (ESRI)
format.

Thanks,
Narayani

? ? ? ?[[alternative HTML version deleted]]

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If you really require square cells, then the resample function in
'raster' might be useful:

library(raster)
r = raster('ncdffile')
# or r=raster(matrix); extent(r) = c( , , , )
s = raster(r)
res(s) = min(res(s))
s = resample(r, s,  method='bilinear')
s = writeRaster(s, filename='abc.asc', format='ascii')

Or first do an interpolation first. Many options for that. E.g. see
?raster::interpolate

Robert
Does it have to be that ascii format? There are much better options
for regular grids, such as GeoTIFF - but it depends on your target of
course. Note that some software supports different dx/dy sizes, namely
GDAL and Golden Surfer for this format:

http://www.gdal.org/frmt_various.html#AAIGrid

If it does need to be ESRI ASCII, you could write it out with square
cells and then reset the cell sizes in the target (if possible).

Is the requirement for square cells with the ESRI version of this
format, or with the software you want to use next?

As a last resort you could resample the grid using R's indexing/seq
functions, or with spsample in package sp, or warp it with an external
tool like gdalwarp.

Cheers, Mike.

On Tue, Feb 2, 2010 at 9:32 AM, Narayani Barve <narayani.ku at gmail.com> wrote:
Hi All,

I want to convert netCDF files to ESRI ASCII grid. I used the package ncdf
to read the file and get the required variable in the matrix format. Now I
want to write this matrix into ESRI ASCII grid. Looking at the extends of
the data, and the row and column dimensions, I know that the CELLSIZE is not
square.

Is there any way, I can convert this data into square ASCII Grid (ESRI)
format.

Thanks,
Narayani

? ? ? ?[[alternative HTML version deleted]]

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo

_______________________________________________
R-sig-Geo mailing list
R-sig-Geo at stat.math.ethz.ch
https://stat.ethz.ch/mailman/listinfo/r-sig-geo