[ncl-talk] Overlay point shapefile on a plot

Rick Brownrigg brownrig at ucar.edu
Thu Jul 6 10:42:11 MDT 2017 

Mary, Lyndon,

Apparently, with GDAL 2.1, a bunch of new spatial types were added from the
"ISO SQL/MM Part 3" spec (a specification for representing spatial data).
Specifically, there were "wkb...Z" and "wkb...M" shapes added to the
so-called well-known binary formats, to reflect shapes that are 3D with
either X,Y,Z coordinates or X,Y,M coordinates ("m" for "measurement"; i.e.,
some arbitrary scalar other than height/altitude).
In this particular case, the file's geometry was wkbPointM, which is
slightly odd because, as there's a Z coordinate, but not an M coord. I
would think it should be wkbPointZ.  (The GrADS page does state however
that Point and Line shapefiles are "measured").  In any case, both types
would be unrecognized as these types were not available when the OGR reader
was initially developed.

As long as we are willing to decree our code requires GDAL >=2.1, the fix
is easy.

Rick

On Thu, Jul 6, 2017 at 9:39 AM, Mary Haley <haley at ucar.edu> wrote:

> Hi Lyndz,
>
> I've filed a ticket on this, NCL-2628. I don't know anything about how
> GrADS writes shapefiles, but it does seem like you are writing the file the
> way the GrADS documentation suggests.
>
> Thanks for providing the files.
>
> --Mary
>
>
> On Wed, Jul 5, 2017 at 7:34 PM, Lyndon Mark Olaguera <
> olagueralyndonmark429 at gmail.com> wrote:
>
>> Dear Mary,
>>
>> Thank you for this. I actually created the shapefile in GRADS (
>> http://cola.gmu.edu/grads/gadoc/shapefiles.html). Like this:
>>
>> ymin=1979
>> ymax=1995
>> 'sdfopen regpval_90%_hgt_'ymin'-'ymax'.nc'
>> *'set gxout shp'*
>> *'set shp -pt -fmt 8 4 sig_regpval_'ymin'-'ymax''*
>> *'set shpattr AUTHOR string LYNDZ'*
>> *'set shpattr TYPE string grid points'*
>> *'set shpattr DESC string sig_regpval_'ymin'-'ymax''*
>> *'d regpval'*
>>
>> For some unknown reason, NCL cannot recognize the geometry type. I
>> checked the metadata in QGIS and the geometry type is "point" (see attached
>> image).
>>
>>
>> Sincerely,
>>
>> *Lyndz*
>>
>>
>> On Thu, Jul 6, 2017 at 1:41 AM, Mary Haley <haley at ucar.edu> wrote:
>>
>>> Hi Lyndon,
>>>
>>> [Thanks Karin for helping out with this.]
>>>
>>> This is the first time I've seen a shapefile that didn't have a
>>> "geometry_type" of "point", "polyline" or "polygon".  As Karin pointed out,
>>> the shapefile should still plot just fine, but I will modifiy the
>>> gsn_add_shapefile_xxxx routines so they are not so restrictive. Instead of
>>> quitting with an error, I'll have them print a warning.
>>>
>>> --Mary
>>>
>>>
>>> On Mon, Jul 3, 2017 at 8:29 AM, Lyndon Mark Olaguera <
>>> olagueralyndonmark429 at gmail.com> wrote:
>>>
>>>> Hi Karin,
>>>>
>>>> I got it very clearly..Thank you so much.
>>>>
>>>> Lyndon
>>>> On 3 Jul 2017 22:40, "Karin Meier-Fleischer" <meier-fleischer at dkrz.de>
>>>> wrote:
>>>>
>>>>> Hi Lyndon,
>>>>>
>>>>> the projection is not the problem I just used the
>>>>> cylindrical-equidistant projection to see the global map.
>>>>>
>>>>> The function gsn_add_shapefile_polymarkers reads the shapefile and
>>>>> scan the global file attribute geometry_type. If it doesn't exist it
>>>>> directly returns to the main script printing the error message.
>>>>> There are two ways to go on, you can copy and edit the
>>>>> gsn_add_shapefile_polymarkers function or you can draw the polymarkers as I
>>>>> did in the modified script using the gsn_add_polymarker function.
>>>>>
>>>>> Bye, Karin
>>>>>
>>>>> Am 03.07.17 um 13:24 schrieb Lyndon Mark Olaguera:
>>>>>
>>>>> Dear Karin,
>>>>>
>>>>>
>>>>> Thank you for the help. Actually, I was able to plot this successfully
>>>>> by editing the shapefile attribute manually in QGIS. I need to plot it in
>>>>> orthographic projection (Similar to the attached).
>>>>>
>>>>> Is it possible to specify the "geometry type" within the code (or edit
>>>>> the shapefile attribute?) after reading the shapefile?
>>>>>
>>>>>
>>>>> Many thanks,
>>>>>
>>>>> Lyndz
>>>>>
>>>>>
>>>>>
>>>>> On Mon, Jul 3, 2017 at 8:09 PM, Karin Meier-Fleischer <
>>>>> meier-fleischer at dkrz.de> wrote:
>>>>>
>>>>>> Hi Lyndon,
>>>>>>
>>>>>> the problem is that your shapefile data does not contain point data
>>>>>> which is needed by gsn_add_shapefile_polymarkers function
>>>>>>
>>>>>> http://ncl.ucar.edu/Document/Graphics/Interfaces/gsn_add_sha
>>>>>> pefile_polymarkers.shtml
>>>>>>
>>>>>> To see what is in your shapefile you can draw the shapefile data
>>>>>> using the x- and y-values. I've attached your modified script and the PNG
>>>>>> plot.
>>>>>>
>>>>>> Hope this helps,
>>>>>> Karin
>>>>>>
>>>>>>
>>>>>> Am 03.07.17 um 04:37 schrieb Lyndon Mark Olaguera:
>>>>>>
>>>>>> Dear NCL experts,
>>>>>>
>>>>>> I am trying to add point shapefile to a plot using the
>>>>>> gsn_add_shapefile_polymarkers function in NCL.
>>>>>>
>>>>>> To view the contents of the shapefile I used the shape_utils.ncl from
>>>>>> the following link:
>>>>>>
>>>>>>
>>>>>> *https://www.ncl.ucar.edu/Applications/shapefiles.shtml
>>>>>> <https://www.ncl.ucar.edu/Applications/shapefiles.shtml> *
>>>>>>
>>>>>> I tried to plot the shapefile in GIS and it works fine but I still
>>>>>> got an error that the geometry attribute should be a point when I plot it
>>>>>> in NCL. I am not sure why in the filedump below, the geometry type is
>>>>>> "unknown".
>>>>>>
>>>>>>
>>>>>> I attached my script and the files that I am plotting.
>>>>>>
>>>>>>
>>>>>> Variable: a
>>>>>> Type: file
>>>>>> File path: may_hgt-hgt_1996-2012_850hPa.nc
>>>>>> Number of global attributes: 0
>>>>>> Number of dimensions: 2
>>>>>> Number of variables: 6
>>>>>> (0) ============================================================
>>>>>> ==========
>>>>>> (0) Filename: "sig_regpval_1996-2012.shp"
>>>>>> (0)   Geometry type: unknown
>>>>>> (0)   # of features: 2906
>>>>>> (0)   Min/max lat:    -80.00/  82.50
>>>>>> (0)   Min/max lon:      0.00/ 360.00
>>>>>> (0)   Variable names and their types:
>>>>>> (0)       geometry : integer
>>>>>> (0)       segments : integer
>>>>>> (0)       x : double
>>>>>> (0)       y : double
>>>>>> (0)       z : double
>>>>>> (0)       CREATED_BY : string
>>>>>> (0)       AUTHOR : string
>>>>>> (0)       TYPE : string
>>>>>> (0)       DESC : string
>>>>>> (0)       LONGITUDE : double
>>>>>> (0)       LATITUDE : double
>>>>>> (0)       GRID_VALUE : double
>>>>>> (0) ============================================================
>>>>>> ==========
>>>>>> (0) Error: gsn_add_shapefile_polymarkers: geometry_type attribute
>>>>>> must be 'point'
>>>>>> (0)       No shapefile information will be added.
>>>>>>
>>>>>>
>>>>>> I'll appreciate any suggestion on how I can plot this correctly.
>>>>>>
>>>>>> Thank you in advance.
>>>>>>
>>>>>> Lyndz
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>> --
>>>>>> Dipl. Geophys. Karin Meier-Fleischer
>>>>>> Visualization, NCL, CDO
>>>>>> Application Support
>>>>>>
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>>>>>> Bundesstrasse 45a - D20146 Hamburg - Germany
>>>>>>
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>>>>>> E-Mail:   meier-fleischer at dkrz.de
>>>>>> URL:      www.dkrz.de
>>>>>>
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>>>>>>
>>>>>> _______________________________________________ ncl-talk mailing
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>>>>>
>>>>> --
>>>>> Dipl. Geophys. Karin Meier-Fleischer
>>>>> Visualization, NCL, CDO
>>>>> Application Support
>>>>>
>>>>> Deutsches Klimarechenzentrum GmbH (DKRZ)
>>>>> Bundesstrasse 45a - D20146 Hamburg - Germany
>>>>>
>>>>> Phone:    +49 (0)40 460094 126 <+49%2040%20460094126>
>>>>> Fax:      +49 (0)40 460094 270 <+49%2040%20460094270>
>>>>> E-Mail:   meier-fleischer at dkrz.de
>>>>> URL:      www.dkrz.de
>>>>>
>>>>> Geschäftsführer: Prof. Dr. Thomas Ludwig
>>>>> Sitz der Gesellschaft: Hamburg
>>>>> Amtsgericht Hamburg HRB 39784
>>>>>
>>>>>
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