[ncl-talk] Pixel to Lat/Lon

[Dave Allured - NOAA Affiliate]

Ipsita,

It looks like you got the coordinates working.  I can't be of much help on
the plotting issues.  I suggest that you look through the NCL examples for
similar plots of swath data.

--Dave


On Thu, Jul 13, 2017 at 6:04 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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