[API-users] projections and occurrence density data

[Daniel McGlinn]

Dear list,

My group has been developing some tools that depend on the occurrence
density data that GBIF provides through its API:

https://www.gbif.org/en/developer/maps

We have been using the R function rgbif::map_fetch to query the api. The
data is returned faithfully but we are experiencing some issues with
projections of the raster data.

I have posted a reproducible example in R here:
https://github.com/ropensci/rgbif/issues/366 . But briefly the issue is
that EPSG:3857 that is downloaded from the API has an extent from -180 to
180 in the x-axis and -86 to 86 in the y-axis but when converting longitude
latitude coordinates into the EPSG:3857 coordinate reference system the
spatial domain is much larger (I think because it is defined in meters
rather than degrees). What am I missing here? I am still a neophyte when it
comes to projections so I apologize if this an obvious question.

One other quick point is that the GBIF maps API does not seem to serve up
the same spatial domain for each projection that is possible. Specifically
compare the following two queries to the api:
https://api.gbif.org/v2/map/occurrence/density/0/0/0@1x.png?srs=EPSG:3857
https://api.gbif.org/v2/map/occurrence/density/0/0/0@1x.png?srs=EPSG:4326

Note that EGSG:4326 is on a smaller spatial domain that does not include
the whole Earth. Maybe this is by design but this webpage led me to believe
differently:  https://tile.gbif.org/ui/ '

Thanks in advance for your help!

Dan

-- 
Daniel J. McGlinn, PhD
Assistant Professor
mailing address:
Department of Biology
College of Charleston
66 George Street
Charleston, SC 29424
https://www.mcglinnlab.org
physical address:
Rita Hollings Science Center (office: 239, lab: 292)
58 Coming Street, Suite 245-255
Charleston, SC 29401
office: 843-953-0190
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