[ncl-talk] Pixel to Lat/Lon

Fri Jul 14 11:42:25 MDT 2017

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
>>>>>>>>>>
>>>>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> ncl-talk mailing list
>>>>>> ncl-talk at ucar.edu
>>>>>> List instructions, subscriber options, unsubscribe:
>>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> ncl-talk mailing list
>>>>> ncl-talk at ucar.edu
>>>>> List instructions, subscriber options, unsubscribe:
>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>
>>>>>
>>>>
>>>
>>
>
> _______________________________________________
> ncl-talk mailing list
> ncl-talk at ucar.edu
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.ucar.edu/pipermail/ncl-talk/attachments/20170714/b059d078/attachment.html 