[ncl-talk] Pixel to Lat/Lon

Fri Jul 14 07:46:37 MDT 2017

Attached is a script that uses ESMF to regrid. Generating the weights is a
bit slow.

On Fri, Jul 14, 2017 at 12:59 AM, Ipsita Putatunda <
ipsita.putatunda at gmail.com> wrote:

> Hi Mary,
>  If I plot in "RasterFill" mode then only the plot is appearing, not even
> I set "AreaFill" or "CellFill".
> The plot is appearing something like fractured, not a smoothed one (even
> though I put smoothing), I don't know why it is like so.
>
> Thanks in advance,
> Ipsita
>
> On Fri, Jul 14, 2017 at 11:34 AM, Ipsita Putatunda <
> ipsita.putatunda at gmail.com> wrote:
>
>> Hi Mary,
>>  I have uploaded my data file with my scripts through ftp.
>>
>> Ipsita
>>
>> On Fri, Jul 14, 2017 at 2:51 AM, Dennis Shea <shea at ucar.edu> wrote:
>>
>>> IMHO: The script is working correctly. However, there is a mismatch
>>> between the
>>> the user's VERY high resolution (0.15 degrees) 'target grid' and the
>>> resolution of the swath data points.
>>>
>>> re:
>>>
>>>  nlat=1200
>>>  nlon=2400
>>>
>>> defines a grid with spacing 0.15 degrees. VERY high resolution
>>>
>>> ====
>>>
>>> I have no idea what the rationale for the '400' used for GBIN and
>>> GKNTwas based upon.
>>>
>>>  GBIN  = new ( (/400,nlon/), float )
>>>  GKNT = new ( (/400,nlon/), integer )
>>>
>>> =====
>>>
>>> The binning algorithm looks at each swath lat/lon location. It finds the
>>> target grid box that 'surrounds'  the current swath lat/lon location.
>>>
>>> If there are target grid boxes which do not surround the swath grid
>>> poins, then they are returned as missing (_FillValue). Hence, the
>>> 'fractured' look of the plot.
>>>
>>> D
>>>
>>>
>>>
>>>
>>>
>>> On Thu, Jul 13, 2017 at 2:52 PM, Mary Haley <haley at ucar.edu> wrote:
>>>
>>>> Hi Ipsita,
>>>>
>>>> I'm not sure what you mean by " even though the plot is not coming
>>>> with a clear contours. "
>>>>
>>>> The plot you included doesn't look particularly wrong, so can you
>>>> explain what you were expecting?
>>>>
>>>> The script you attached does not include any plotting code, so I can't
>>>> help you much there.
>>>>
>>>> Can you be more specific about the problem?  Also, it would really help
>>>> if you can provide the data and the plotting script in the usual way (ftp).
>>>>
>>>> Thanks,
>>>>
>>>> --Mary
>>>>
>>>>
>>>>
>>>>
>>>> On Thu, Jul 13, 2017 at 7:04 AM, Ipsita Putatunda <
>>>> ipsita.putatunda at gmail.com> wrote:
>>>>
>>>>> Thank you Dave for your suggestions. I tried to plot the data, but it
>>>>> is coming only if I plot setting resource "RasterFill", and even though the
>>>>> plot is not coming with a clear contours. Don't know where I am making
>>>>> mistake. I tried to regrid the data using "triple2grid" but then all the
>>>>> values are coming undefined. I am attaching herewith my script and the
>>>>> figure I have got after plotting. Any help will be appreciated.
>>>>> Thanks in advance.
>>>>>
>>>>> Ipsita
>>>>>
>>>>>
>>>>> On Thu, Jul 13, 2017 at 4:19 AM, Dave Allured - NOAA Affiliate <
>>>>> dave.allured at noaa.gov> wrote:
>>>>>
>>>>>> Ipsita,
>>>>>>
>>>>>> This HDF5 file has coordinate arrays Colatitude and Longitude.  The
>>>>>> units of each are degrees, not pixels.  However, please notice two
>>>>>> anomalies:
>>>>>>
>>>>>> 1.  The coordinates are packed with an unusual scale/offset packing
>>>>>> scheme.  The packing parameters are in attributes Scale_Factor and
>>>>>> Add_Offset, which are not CF standard attributes.  However, the intent is
>>>>>> fairly clear.  To unpack each coordinate value, just multiply by the
>>>>>> Scale_Factor.
>>>>>>
>>>>>> The Add_Offset's are zero in this case, and can therefore be
>>>>>> ignored.  That is good, so that we do not have to worry about whether the
>>>>>> offset would be applied before or after the scale factor.
>>>>>>
>>>>>> This will produce colatitudes in the normal range 60 to 120 degrees,
>>>>>> and longitudes in the normal range 0 to 360 degrees.
>>>>>>
>>>>>> 2.  I assume that the colatitudes conform to the current definition
>>>>>> on Wikipedia.  You might confirm this with the data provider, if you wish.
>>>>>> This definition is the number of degrees southward from the north pole.
>>>>>> The colatitude values unpacked are in the range 60 to 120 degrees, which
>>>>>> translate to 30 north to 30 south in normal latitude units.
>>>>>>
>>>>>> --Dave
>>>>>>
>>>>>>
>>>>>> On Wed, Jul 12, 2017 at 12:08 AM, Ipsita Putatunda <
>>>>>> ipsita.putatunda at gmail.com> wrote:
>>>>>>
>>>>>>> The Latitude (here Colatitude) and Longitude data are in pixels
>>>>>>> which is -30 to 30 degree and 0 to 360 degree. Please find the file I am
>>>>>>> attaching herewith.
>>>>>>>
>>>>>>> Ipsita
>>>>>>>
>>>>>>> On Tue, Jul 11, 2017 at 10:30 PM, Dave Allured - NOAA Affiliate <
>>>>>>> dave.allured at noaa.gov> wrote:
>>>>>>>
>>>>>>>> Ipsita,
>>>>>>>>
>>>>>>>> How is your input data georeferenced?  Does the input file include
>>>>>>>> coordinate variables?  That is the most common way to get lats and lons for
>>>>>>>> individual pixels.
>>>>>>>>
>>>>>>>> --Dave
>>>>>>>> (Please reply to the mailing list.)
>>>>>>>>
>>>>>>>>
>>>>>>>> On Tue, Jul 11, 2017 at 12:22 AM, Ipsita Putatunda <
>>>>>>>> ipsita.putatunda at gmail.com> wrote:
>>>>>>>>
>>>>>>>>> Dear NCL users,
>>>>>>>>>   I need help in converting pixels to Lat/Lon grid. Is there any
>>>>>>>>> function or way in ncl for doing this operation? Please suggest.
>>>>>>>>>
>>>>>>>>> Thanks in advance,
>>>>>>>>> Ipsita
>>>>>>>>>
>>>>>>>>
>>>>>
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>
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