Hello again,
I have a similar problem, this time on NOAA grib 2 data with LatLon
projection.
values are flipped along the latitude axis again (same as bug 2 I
reported previously)
this starts to make me think the problem might be in geotoolkit.
But usual netcdf files are displayed properly ...
I would like to have a confirmation, here is a partial dump obtained
with class NCDumpW :
What I would like to know is : the line marked #1 is for latitude +78 or
-78 ?
netcdf /..../somegrib.grib2 {
dimensions:
lon = 288;
lat = 157;
time = 61;
variables:
float lat(lat=157);
:units = "degrees_north";
float lon(lon=288);
:units = "degrees_east";
int time(time=61);
:units = "Hour since 2012-10-30T06:00:00.000Z";
:standard_name = "time";
float Wind_direction_from_which_blowing_degree_true_surface(time=61,
lat=157, lon=288);
:long_name = "Wind direction (from which blowing) (degree true) @
Ground or water surface";
:units = "deg";
:missing_value = NaNf; // float
:abbreviation = "WDIR";
:grid_mapping = "LatLon_Projection";
:Grib_Variable_Id = "VAR_0-2-0_L1";
:Grib2_Parameter = 0, 2, 0; // int
:Grib2_Level_Type = 1; // int
:Grib2_Generating_Process_Type = "Forecast";
....
data:
lat =
{78.0, 77.0, 76.0, 75.0, 74.0, 73.0, 72.0, 71.0, ... , -74.0, -75.0,
-76.0, -77.0, -78.0}
lon =
{0.0, 1.25, 2.5, 3.75, 5.0, 6.25, 7.5, 8.75, 10.0, ... , 355.0,
356.25, 357.5, 358.75}
time =
{0, 3, 6, 9, 12, 15, 18, 21, 24, ... , 174, 177, 180}
Wind_direction_from_which_blowing_degree_true_surface =
{
{
{56.78, 57.72, 61.87,... }, #1
{56.78, 57.72, 61.87,... },
{107.14, ... },
...
}
}
thanks.
Johann Sorel
On 02/11/2012 02:18, John Caron wrote:
Hi johann :
Thanks very much, these fixes will be in target-4.3.14 later tonight.
John
On 10/31/2012 5:41 AM, johann sorel wrote:
Hello,
I work with martin desruisseaux on the geotoolkit.org project.
While trying to access datas from :
http://www.globalmarinenet.com/grib_downloads.php I found a few bugs in
the grib1 to netcdf metamodel.
Those are GRIB 1 files with LatLon projections.
grib/src/main/java/ucar/nc2/grib/grib1/Grib1Gds.java$LatLon
There was 2 bugs in this projection creation :
1 - a copy/paste error when calculating the latitude delta.
if (!Misc.closeEnough(deltaLat, calcDelta)) {
log.debug("deltaLat != calcDeltaLat");
deltaLat = calcDelta; ----> was deltaLon = calcDelta;
}
2 - wrong value order when datas start by the lower values.
BEFORE
if (deltaLat != GribNumbers.UNDEFINED) {
deltaLat *= scale3; // undefined for thin grids
if (la2 < la1) deltaLat *= -1.0;
} else deltaLat = calcDelta;
AFTER
if (deltaLat != GribNumbers.UNDEFINED) {
deltaLat *= scale3; // undefined for thin grids
if (la2 < la1) {
//flip declaration order
float latemp = la1;
la1 = la2;
la2 = latemp;
calcDelta *= -1.0;
//we must also consider the cell corner, since we flipped
the order
//we should specify that the true value is at the
BOTTOM-LEFT corner
//but we can't show this information so we make a one cell
displacement
//to move the value on a TOP-LEFT corner.
la1 -= calcDelta;
la2 -= calcDelta;
}
} else {
deltaLat = calcDelta;
}
I attached a snapshot of the visualized datas before and after fix over
the indian ocean and the patched java class.
Johann Sorel
Geomatys
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