[ncl-talk] convert polyline shapefile to netcdf via ncl_convert2nc

[Dennis Shea]

http://www.ncl.ucar.edu/Applications/binning.shtml

See Example 2:

  freq  = count
  freq  = (count/npts)*100   ; comment this


On Sat, Apr 7, 2018 at 9:05 PM, Lyndz <olagueralyndonmark429 at gmail.com>
wrote:

> Hi Sir Rick,
>
> Thank you for the fast response.
> I wanted to create a 5degree by 5degree grid NetCDF file from the
> shapefile, where each grid box contains the "count"(frequency) of unique TC
> tracks per category.
> I'm just wondering if this is possible to do in NCL.
>
> Sincerely,
>
> Lyndz
>
>
> On Sun, Apr 8, 2018 at 3:34 AM, Rick Brownrigg <brownrig at ucar.edu> wrote:
>
>> Hi Lyndz,
>>
>> I'm not sure there is a "correct" way to do this. NetCDF is really good
>> at representing regular arrays of data, whereas polylines/polygons tend to
>> have varying numbers of coordinate pairs -- what would lat and lon
>> variables look like in that case, and what would be the meaning of lat/lon
>> dimensions?  NCL makes a shapefile *look* like a NetCDF file by packing the
>> coordinate information for all features into the x/y variables, but then
>> one has to utilize the geometry and segments variables to unpack
>> coordinates for each feature. The shapefiles examples page show many
>> examples of doing this:
>>
>>     http://ncl.ucar.edu/Applications/shapefiles.shtml
>>
>> If you are working with NCL, you are probably better off leaving your
>> data as a shapefile*. *I take it however that you have other reasons for
>> wanting a NetCDF file?
>>
>> Finally, I might comment that the conversion result may not be correct --
>> its suspect to me that the "num_points" value is exactly twice the value of
>> "num_features" -- I wonder if maybe just the end-points of the tracks where
>> what got captured in the conversion?
>>
>> Rick
>>
>> On Fri, Apr 6, 2018 at 11:30 PM, Lyndz <olagueralyndonmark429 at gmail.com>
>> wrote:
>>
>>> Dear NCL experts,
>>>
>>> I would like to convert the following shapefile to a netcdf file.
>>> I created the shapefile from a csv file containing jtwc tc tracks (see
>>> attached csv2shp.py)
>>> Also attached is the csv file.
>>>
>>> When I used the ncl_convert2nc the netcdf file has no lat-lon dimension.
>>> Here's the output of the ncdump. Is it also possible to divide the TC
>>> categories by dividing the Vmax values?
>>>
>>>
>>> I'll appreciate any suggestion on how to do this correctly.
>>>
>>>
>>> netcdf par_jtwc_above_ts_1979-1993 {
>>> dimensions:
>>> geometry = 2 ;
>>> segments = 2 ;
>>> num_features = 1050 ;
>>> num_segments = 1050 ;
>>> num_points = 2100 ;
>>> variables:
>>> int geometry(num_features, geometry) ;
>>> int segments(num_segments, segments) ;
>>> double x(num_points) ;
>>> double y(num_points) ;
>>> int SN(num_features) ;
>>> int CY(num_features) ;
>>> int Y1(num_features) ;
>>> int M1(num_features) ;
>>> int D1(num_features) ;
>>> int H1(num_features) ;
>>> int VMax1(num_features) ;
>>> int Y2(num_features) ;
>>> int M2(num_features) ;
>>> int D2(num_features) ;
>>> int H2(num_features) ;
>>> int VMax2(num_features) ;
>>>
>>> // global attributes:
>>> :segs_numPnts = 1 ;
>>> :segs_xyzIndex = 0 ;
>>> :geom_numSegs = 1 ;
>>> :geom_segIndex = 0 ;
>>> :geometry_type = "polyline" ;
>>> :layer_name = "par_jtwc_above_ts_1979-1993" ;
>>> :creation_date = "Sat Apr  7 14:11:24 JST 2018" ;
>>> :NCL_Version = "6.4.0" ;
>>> :system = "Linux localhost.localdomain 3.10.0-327.36.3.el7.x86_64 #1 SMP
>>> Mon Oct 24 16:09:20 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux" ;
>>> :Conventions = "None" ;
>>> :title = "NCL: convert-OGR-to-netCDF" ;
>>> }
>>>
>>>
>>> Sincerely,
>>>
>>> Lyndz
>>>
>>>
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>>>
>>
>
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