Re: geographic plotting

[Manfred S. <man...@gm...>]

Am 07.03.20 um 00:58 schrieb Ethan A Merritt:
> On Wednesday, 4 March 2020 12:34:45 PST Allin Cottrell wrote:
>> On Wed, 4 Mar 2020, Manfred Schwarb wrote:
>>
>>> More to the topic, I think the shape format is proprietary,
>>> complicated, spread over multiple files, limited (number of
>>> fields, length of field names, file size,...), so in one word:
>>> "legacy".
>>>
>>> So I don't think it is an appropriate format for interfacing with
>>> gnuplot. I made positive experiences with GeoJSON, it is a simple,
>>> very versatile format, and I think most GIS programs can read and
>>> write this format, so why not use some geojson routine and put it
>>> into gnuplot?
>>
>> I'm all in favor of nicer and non-proprietary formats, but what's
>> the comparison in terms of availability of files representing
>> polygons one might want (US states, counties or commuting zones, EU
>> countries or regions, etc.)? It's my impression that you can easily
>> pick up shapefiles for any/all of these -- nasty as the format may
>> be -- but what about GeoJSON files?
>>
>> Allin Cottrell

Allin, of course you are right, I guess there are almost no public GeoJSON
polygon files available.
GeoJSON is more of a intermediate format to transfer data from one application
to another one.

For me the choice of a pure shapefile solution simply sounds a bit wierd,
either a very slim solution supporting some simple format or a full-fledged
solution using libgdal (which supports ~50 different formats) would make sense.

>
> Good call.  Geojson looks quite promising.
> A real parser should be easy, but even a quick pass through sed
> or a text editor makes it usable.
> I have posted a proof-of-principle example using US state boundary
> data from a sample file on the geojson development site:
>
>   http://skuld.bmsc.washington.edu/people/merritt/gnuplot/
>

Thanks for the example.
Often the issue is, that the provided shapefiles are a complete mess and you have to
extract some polygons from it. With geojson, at least with the variant that gdal writes,
this is very simple: Each polygon is on its own line.
So, assuming the polygons are annotated, you can grep for a polygon and re-add header and
footer afterwards.

> 	Ethan
>
>
>
>
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