[API-users] Clipping occurrence data to a country
Adriaan van Os
adriaan at adriaan.biz
Thu Jan 10 11:10:09 CET 2019
Matthew Blissett wrote:
> For the other approach, I don't have EPSG:3575-format vector tiles with
> country borders, but in any case it's difficult to work with vector
> tiles for any further processing â€” if you wanted a polygon, you'd need
> to reconstruct it from the lines which are cut off at the edges of the
> tiles. I recommend you use a different source of map data, e.g. from
> http://www.naturalearthdata.com/ . Many GIS libraries (including
> example in GeoJSON format:
With some programming, the poly-edge cutting problem can be solved. Besides, on large-scale maps
with small polys, I find cutting the poly edges really improves the looks of the map. Also, one
could use the country borders to highlight (e.g.) a specific country on the background-map before
overlaying the occurrence polys. So, I do suggest adding "&country=" to the GBIF background-map
> https://github.com/nvkelso/natural-earth-vector/tree/master/geojson (if
> 10m resolution is sufficient).
The Natural Earth Admin0 data sets
<https://www.naturalearthdata.com/downloads/50m-cultural-vectors/> are what I need. Best of all, it
can be loaded into QGiS and converts perfectly well to EGCS:3575. There is not much on the internet
(that I could find) for converting to EGCS:3575. I have only located QGiS, OpenLayers (apparently)
and Leaflet (Proj4Leaflet c.s.). And GBIF, of course.
The advantage of EGCS:3575 is that it is an equal area projection
<https://en.wikipedia.org/wiki/Lambert_azimuthal_equal-area_projection>, unlike EPSG:3857 Web
Mercator. I don't like Web Mercator distortions. I guess EPSG:3857 became polular when Google
started to use it, thinking that people will be confused when the line pointing North isn't
vertical. God should have made the earth a cube for that purpose ? Well, that causes some problems
at the edges when travelling ....
I will investigate the &country=NL issue further and reply seperately.
Adriaan van Os
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