[ncl-talk] Fwd: Random file into polar coordinates

Wed Nov 8 19:27:27 MST 2017

---
re:
I have latitude and longitude in cartesian coordinates (example of the text
file is above). That is the only information I have. I plotted the data
before using gsn_add_polymarker for the domain I want e.g. 15N 20N and
54W-58W. The center of this domain is 16.8N and 56W. What the polymaker
function did was if I had an observation at 16N and 53W a black dot was
drawn. What I need now is transform that 16N-53W (black dot)
into cylindrical coordinates using as center 16.8N and 56W.
---

This is much more specific. Really, this needs custom built code:

[a] The region is quite small and near the equator. Hence, I think you
could treat the data as being on a cartesian grid.

  clat =  16.8    ; user specified center point
  clon = -56.0

  latS =  15.0    ; area of interest; nearish to equator; earth curvature
effect is 'small'
  latN =  20.0
  lonL = -58.0
  lonR = -54.0

[b] You can use the 'ind' function to isolate only points with the region
of interest:
      https://www.ncl.ucar.edu/Document/Functions/Built-in/ind.shtml

[c] You specified a center point. You could use the following to determine
the radius (distance) to each point.
     https://www.ncl.ucar.edu/Document/Functions/Built-in/gc_latlon.shtml

[d] I think the  polar 'theta' can be determined using atan2.
      https://www.ncl.ucar.edu/Document/Functions/Built-in/atan2.shtml

---
It is your responsibility to read the documentation and test with your
data. Look at the printed output. Maybe, for a point or two, manuall dray a
picture.

---
See attached ...

Good Luck

On Wed, Nov 8, 2017 at 12:45 PM, Mary Haley <haley at ucar.edu> wrote:

> Please see our r, theta plotting examples page at:
>
> http://www.ncl.ucar.edu/Applications/radar.shtml
>
> To be honest, NCL is not tailored for r, theta data, but it *is* possible
> to plot it. You have to do some of the work to convert to the coordinate
> system you want.
>
> --Mary
>
>
> On Tue, Nov 7, 2017 at 7:42 PM, Keren Rosado <keren.rosadova at gmail.com>
> wrote:
>
>>
>>
>> Sent from my iPhone
>>
>> Begin forwarded message:
>>
>> *From:* Keren Rosado <keren.rosadova at gmail.com>
>> *Date:* November 7, 2017 at 4:10:01 PM MST
>> *To:* Dennis Shea <shea at ucar.edu>
>> *Subject:* *Re: [ncl-talk] Fwd: Random file into polar coordinates*
>>
>> I have latitude and longitude in cartesian coordinates (example of the
>> text file is above). That is the only information I have. I plotted the
>> data before using gsn_add_polymarker for the domain I want e.g. 15N 20N
>> and 54W-58W. The center of this domain is 16.8N and 56W. What the polymaker
>> function did was if I had an observation at 16N and 53W a black dot was
>> drawn. What I need now is transform that 16N-53W (black dot)
>> into cylindrical coordinates using as center 16.8N and 56W.
>>
>> On Tue, Nov 7, 2017 at 3:25 PM, Dennis Shea <shea at ucar.edu> wrote:
>>
>>> Again you need clarify  even more ...Please look at:
>>>
>>> ---
>>>
>>>  http://hyperphysics.phy-astr.gsu.edu/hbase/sphc.html
>>>
>>> Upper left:
>>>
>>> theta is (90-latitude); co-latitude
>>> phi is longitude
>>> r is the radius of the earth (assuming a spherical earth)
>>>
>>> You have all of this information.
>>>
>>> ===
>>> http://keisan.casio.com/exec/system/1359534351
>>> ===
>>> The radius at any latitude:
>>>    http://mathforum.org/library/drmath/view/54158.html
>>>
>>> r(latitude) = r*cos(latitude)   ; latitude in radians
>>>
>>>
>>>
>>>
>>> On Tue, Nov 7, 2017 at 1:07 PM, Keren Rosado <keren.rosadova at gmail.com>
>>> wrote:
>>>
>>>> R, theta
>>>>
>>>> On Tue, Nov 7, 2017 at 12:11 PM, Dennis Shea <shea at ucar.edu> wrote:
>>>>
>>>>> Please clarify your question:
>>>>>
>>>>> re: "polar coordinates"
>>>>>
>>>>> (a)  r,theta ?  https://en.wikipedia.org/wiki/Polar_coordinate_system
>>>>> (b)  lat,lon ?
>>>>>
>>>>> On Tue, Nov 7, 2017 at 11:52 AM, Keren Rosado <
>>>>> keren.rosadova at gmail.com> wrote:
>>>>>
>>>>>>
>>>>>> Hello,
>>>>>>
>>>>>> I have a file with observations for the entire globe for one hour
>>>>>> period.
>>>>>> Here are few lines from my txt (observations) files. The highlighted
>>>>>> values are for lat and lon:
>>>>>> 2010/08/28,04:00:00.356732, 11.7047, 133.9177,  4.8,  5
>>>>>>
>>>>>> 2010/08/28,04:00:00.629722, 36.7353,  52.1856, 26.8,  7
>>>>>>
>>>>>> 2010/08/28,04:00:00.559602, 36.8155,  52.2482,  3.3,  5
>>>>>>
>>>>>> 2010/08/28,04:00:00.922721,  4.8667, 105.7474,  8.3,  7
>>>>>>
>>>>>> 2010/08/28,04:00:00.130999, 22.7165,-105.1758, 24.9,  5
>>>>>>
>>>>>> 2010/08/28,04:00:00.400279, 11.7329, 133.9220, 16.3,  9
>>>>>>
>>>>>> 2010/08/28,04:00:01.330873, 21.6459,-105.0242,  7.3,  5
>>>>>>
>>>>>> 2010/08/28,04:00:01.409443, 28.4564, -90.7360,  9.7,  5
>>>>>>
>>>>>>
>>>>>>
>>>>>> I plotted these observations using ncl function gsn_add_polymarker
>>>>>> for the domain I am interested in lat and lon.
>>>>>>
>>>>>>
>>>>>> I will like to now how to transform the lat and lon to polar
>>>>>> coordinates for the domain I am interested.
>>>>>>
>>>>>>
>>>>>> Does anyone have an idea of how to to this?
>>>>>>
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> ncl-talk mailing list
>>>>>> ncl-talk at ucar.edu
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>>>>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
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>
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