[ncl-talk] Pixel to Lat/Lon
Dennis Shea
shea at ucar.edu
Mon Jul 17 08:44:11 MDT 2017
On Sun, Jul 16, 2017 at 10:54 PM, Dennis Shea <shea at ucar.edu> wrote:
> The attached shows
>
> [top] a plot of the raw data
> [middle] plot from the bin_sum [avg] onto the original high res grid
> [bottom] using 'poisson_grid_fill' and then using a do loop on [2] to
> filter points outside the original swaths.
>
> I do not recommend extrapolation beyond the original region. Extrapolation
> is 'always' dangerous unless it is based upon physical principles.
>
> See attached,
>
> ====
> Please note using the one data file I have ... look at the max/min from
> the original data and GBIN
>
> Variable: data
> Dimensions and sizes: [2383] x [51] <=== original
> units : Watts/m**2
> long_name : Flux_Longwave_TOA
> _FillValue : 32767
> (0) Flux_Longwave_TOA (Watts/m**2) : min=50 max=313.88 <=== original
>
> =====
> Variable: GBIN
> Dimensions and sizes: [lat | 400] x [lon | 2400] <=== target grid
> Coordinates:
> lat: [-29.925..29.92501]
> lon: [0.075..359.925]
> Number Of Attributes: 3
> units : Watts/m**2
> long_name : BINNED: Flux_Longwave_TOA
> _FillValue : 9.96921e+36
> (0) BINNED: Flux_Longwave_TOA (Watts/m**2) : min=50 max=313.88
> <=== Note
> (0) GBIN: nmsg=849042 <=== large number of missing values
> (0) -----
>
> Variable: GKNT
> Type: integer
> Dimensions and sizes: [lat | 400] x [lon | 2400]
> Coordinates:
> lat: [-29.925..29.92501]
> lon: [0.075..359.925]
> Number Of Attributes: 2
> long_name : BINNED COUNT: Flux_Longwave_TOA
> _FillValue : -2147483647 <(214)%20748-3647>
> (0) BINNED COUNT: Flux_Longwave_TOA : min=1 max=3 <=== Note
>
> On Sun, Jul 16, 2017 at 12:36 PM, Ipsita Putatunda <
> ipsita.putatunda at gmail.com> wrote:
>
>> 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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