Hi Bob:
Any word from NCEP on this issue? Or sample files that already use scanmode
64?
John
On Wed, Jan 14, 2015 at 10:30 AM, Bob Lipschutz - NOAA Affiliate <
robert.c.lipschutz@xxxxxxxx> wrote:
> John,
>
> Thanks for looking at this. Sorry, I don't have any particular
> recommendation here. The grid specification does seem odd and inconsistent
> with other domains with scanMode=64 that give south-to-north corner
> coordinates. It's also inconsistent with the similar 1/12th degree '173'
> grid, which has scanMode=0 and north-to-south corners. We will check with
> NCEP to see if there's an error in the table, but it's not a new entry and
> ostensibly used by someone out there (it's described as a Sea Ice grid)...
>
> Thanks again,
>
> -Bob
>
> On Wed, Jan 14, 2015 at 1:14 AM, Bonny Strong - NOAA Affiliate <
> bonny.strong@xxxxxxxx> wrote:
>
>> John, I don't have Bob's expertise, but I know that during discussions
>> here at GSD trying to figure this out, one developer gave his opinion that
>> the lats of the first and last point were unrelated related to the scan
>> direction. Bob may wish to add to that tomorrow.
>>
>> Bonny
>>
>> On Tue, Jan 13, 2015 at 6:07 PM, John Caron <caron@xxxxxxxx> wrote:
>>
>>> Hi Bob:
>>>
>>> Thanks for reporting this problem. Im looking at it now. Do you have any
>>> idea how these various parameters interact? They have first lat in north,
>>> last lat in south, but a positive Dj. Then with scanMode 64, they say
>>> "Points of first row or column scan in the +j (+y) direction". Seems
>>> overspecified with the possibility of inconsistent results. Im looking
>>> though my data samples now to see if I can detect if there is are problems,
>>> but im not exactly sure what combinations should be legal. Any thoughts?
>>>
>>> heres my dump on your record:
>>>
>>> 47: La1 -
>>> latitude of first grid point == 89938000
>>> 56: La2 -
>>> latitude of last grid point == -89938000
>>> 68: Dj
>>> - j direction increment == 125000
>>> 72:
>>> Scanning mode == 64
>>>
>>>
>>>
>>>
>>>
>>> On Mon, Jan 12, 2015 at 4:02 PM, Bob Lipschutz - NOAA Affiliate <
>>> Robert.C.Lipschutz@xxxxxxxx> wrote:
>>>
>>>>
>>>> Java NetCDF Folks,
>>>>
>>>> We have recently begun generating global 1/8 degree GRIB files
>>>> using NCEP's grid 174 definition (
>>>> http://www.nco.ncep.noaa.gov/pmb/docs/on388/tableb.html#GRID174).
>>>>
>>>> Following that definition, we are setting the value of scanMode to 64,
>>>> which
>>>> per GRIB2 Table 3.4 indicates "points scan in the +j direction", and so
>>>> filling
>>>> the data arrays from south to north. However, the java-netCDF package
>>>> (v4.5)
>>>> does not seem to handle the scanMode flag properly, and consequently our
>>>> grids appear flipped on display. Meanwhile, I understand that NCL does
>>>> handle
>>>> the data mapping correctly, from which we conclude that java-netCDF is
>>>> has a
>>>> problem with this grid definition.
>>>>
>>>> As a work-around, we will set scanMode to 0 and write from north to
>>>> south,
>>>> which will fix the problem for us. But, we'd also hope to have the
>>>> tools work
>>>> correctly, too so that we can use the NCEP's grid as specified -- which
>>>> admittedly is strange in that it list the corner lons from north to
>>>> south.
>>>>
>>>> I've posted a sample GRIB2 file and resulting flipped image here:
>>>>
>>>> ftp://aftp.fsl.noaa.gov/divisions/its/bob/grid174_scanmode_64_example.grb2
>>>> ftp://aftp.fsl.noaa.gov/divisions/its/bob/flipped_174grid.jpg
>>>>
>>>> FWIW, here is the output from the (v4.3) Grib2Dump utility on that data
>>>> file:
>>>>
>>>> Header : GRIB2
>>>> Discipline : 0 Meteorological
>>>> products
>>>> GRIB Edition : 2
>>>> GRIB length : 2808735
>>>> Originating Center : 59 The NOAA Forecast
>>>> Systems Laboratory
>>>> Originating Sub-Center : 0
>>>> Significance of Reference Time : 1 Start of forecast
>>>> Reference Time : 2015-01-08T00:00:00Z
>>>> Product Status : 0 Operational products
>>>> Product Type : 1 Forecast products
>>>> Number of data points : 4147200
>>>> Grid Name : 0 Latitude_Longitude
>>>> Grid Shape: 0 Earth spherical with
>>>> radius = 6,367,470 m
>>>> Number of points along parallel: 2880
>>>> Number of points along meridian: 1440
>>>> Basic angle : 0
>>>> Subdivisions of basic angle: 0
>>>> Latitude of first grid point : 89.938
>>>> Longitude of first grid point : 0.062
>>>> Resolution & Component flags : 48
>>>> Winds : True
>>>> Latitude of last grid point : -89.938
>>>> Longitude of last grid point : 359.938
>>>> i direction increment : 0.125
>>>> j direction increment : 0.125
>>>> Grid Units : degrees
>>>> Scanning mode : 64
>>>> Product Definition : 0 Analysis/forecast
>>>> at horizontal level/layer at a point in time
>>>> Parameter Category : 0 Temperature
>>>> Parameter Name : 0 Temperature
>>>> Parameter Units : K
>>>> Generating Process Type : 2 Forecast
>>>> ForecastTime : 240
>>>> First Surface Type : 1 Ground or water
>>>> surface
>>>> First Surface value : 0.0
>>>> Second Surface Type : 255 Missing
>>>> Second Surface value : 0.0
>>>>
>>>> Thanks for any insights on this issue!
>>>>
>>>> Bob Lipschutz
>>>> NOAA/ESRL/Global Systems Division
>>>> IT Services/Data Services Group
>>>>
>>>>
>>>> _______________________________________________
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>>>> netcdf-java@xxxxxxxxxxxxxxxx
>>>> For list information or to unsubscribe, visit:
>>>> http://www.unidata.ucar.edu/mailing_lists/
>>>>
>>>>
>>>
>>
>>
>> --
>> Bonny Strong
>> NOAA Affiliate
>> 303 497-3936
>>
>
>
