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

[Lyndz]

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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