[ncl-talk] Pixel to Lat/Lon

Sun Jul 16 12:36:10 MDT 2017

Hi all,
Thanks a lot for your help. But I have one more doubt. I ran the script
attached by Dennis (Both without any regridding, and with bin_avg), but the
maximum value of Longwave_Flux_TOA is coming more than 1200 both the cases,
where as the data definition is saying the range of the value is (0 to
500). Why is it so?

Thanks,
Ipsita

On Fri, Jul 14, 2017 at 11:12 PM, Dave Allured - NOAA Affiliate <
dave.allured at noaa.gov> wrote:

> Ipsita et al,
>
> I think you can plot this swath data directly, without regridding.  This
> would require conforming arrays of 2-dimensional latitudes and longitudes.
> But guess what?  That's what we figured out two days ago.   ;-)
>
> If this works, I think the plot would look better and plot faster.  Sorry
> I did not think of this sooner.
>
> --Dave
>
>
> On Fri, Jul 14, 2017 at 7:46 AM, Dennis Shea <shea at ucar.edu> wrote:
>
>> 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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