[R] How to open grib file in R?

[Jonsson]

I have this https://echange-fichiers.inra.fr/get?k=6TdTdezNeZwAqJtpwVm
grib file which is a regular lat-lon 0.25x0.25 degrees and contains 4 fields
.
I tried to open it using :
grib <-
readGDAL("C:\\Users\\aalyaari\\Desktop\\Vol_025_H14_2010060700.grib")

but I got this error:
C:\Users\aalyaari\Desktop\Vol_025_H14_2010060700.grib has GDAL driver GRIB
and has 721 rows and 1440 columns Error in validityMethod(as(object,
superClass)) :
Geographical CRS given to non-conformant data: -90.125 90.125

Any idea why I am getting this error?




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[Barry Rowlingson]

On Mon, Jan 14, 2013 at 4:36 PM, Jonsson <amen.a...@bordeaux.inra.fr> wrote:

> but I got this error:
> C:\Users\aalyaari\Desktop\Vol_025_H14_2010060700.grib has GDAL driver GRIB
> and has 721 rows and 1440 columns Error in validityMethod(as(object,
> superClass)) :
> Geographical CRS given to non-conformant data: -90.125 90.125
>
> Any idea why I am getting this error?
>

At a guess, and this is just a guess, I'd say the system tried to
give a Geographical CRS to non-conformant data...

So, what's a Geographical CRS? One with latitude and longitude.
What's "non-conformant data"? Data that can't conform to latitude and
longitude. Why is -90.125 not conformable to latitude-longitude?
Because it's further south than the south pole.

Why have you got data that goes further south than the south pole and
further north than the north pole? I don't know. I suspect you have
points at the poles and the software thinks these are grid cells that
are 0.250 lat-long degrees wide. Ask your source.

For what its worth, the raster package will ignore the error, but
reveals another:

> g=raster("Vol_025_H14_2010060700.grib")
Warning: Inside GRIB2Inventory, Message # 5
ERROR: Ran out of file reading SECT0
There were 76 trailing bytes in the file.
> g
class : RasterLayer
band : 1
dimensions : 721, 1440, 1038240 (nrow, ncol, ncell)
resolution : 0.25, 0.25 (x, y)
extent : -0.125, 359.875, -90.125, 90.125 (xmin, xmax, ymin, ymax)
coord. ref. : +proj=longlat +a=6367470 +b=6367470 +no_defs
data source : /nobackup/rowlings/Downloads/Vol_025_H14_2010060700.grib
names : Vol_025_H14_2010060700

I suspect there's an off-by-one error in the code that created this.
Remember there are only three possible mistakes in computing - off by
one errors and divide by zero errors.

Barry

[Jeff Newmiller]

Your question should have been posted to the R-sig-geo mailing list.

FWIW I have no direct experience with the files or functions you are using, but I have to say the error message seems pretty clear to me: latitude values are normally limited to [-90,90], but your file appears to have data outside this range. Thus, the file appears to have invalid data.
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[Jonsson]

I have just contacted the sources and I am told that he checked min/max
lat/lon for the file and it was right. He is using Linux while I am using
Windows, would that be problematic?




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[Barry Rowlingson]

On Mon, Jan 14, 2013 at 6:26 PM, Jonsson <amen.a...@bordeaux.inra.fr> wrote:
> I have just contacted the sources and I am told that he checked min/max
> lat/lon for the file and it was right. He is using Linux while I am using
> Windows, would that be problematic?

gdalinfo on a Linux box says it has the same problem:

$ gdalinfo Vol_025_H14_2010060700.grib

Warning: Inside GRIB2Inventory, Message # 5
ERROR: Ran out of file reading SECT0
There were 76 trailing bytes in the file.

Driver: GRIB/GRIdded Binary (.grb)
Files: Vol_025_H14_2010060700.grib
Size is 1440, 721
Coordinate System is:
GEOGCS["Coordinate System imported from GRIB file",
DATUM["unknown",
SPHEROID["Sphere",6367470,0]],
PRIMEM["Greenwich",0],
UNIT["degree",0.0174532925199433]]
Origin = (-0.125000000000000,90.125000000000000)
Pixel Size = (0.250000000000000,-0.250000000000000)
Corner Coordinates:
Upper Left ( -0.1250000, 90.1250000) ( 0d 7'30.00"W, 90d 7'30.00"N)
Lower Left ( -0.1250000, -90.1250000) ( 0d 7'30.00"W, 90d 7'30.00"S)
Upper Right ( 359.875, 90.125) (359d52'30.00"E, 90d 7'30.00"N)
Lower Right ( 359.875, -90.125) (359d52'30.00"E, 90d 7'30.00"S)
Center ( 179.8750000, 0.0000000) (179d52'30.00"E, 0d 0' 0.01"N)

Now go ask your source why they are using 721 pixels from N to S...

I don't have anything else that can read grib files, so I can't say
any more, and as a binary file format its hard to tell if gdalinfo is
correct or not, but its usually pretty good.