WIP: Updating to PROJ 6+ proj.h C API #1252

snowman2 · 2018-12-31T20:32:39Z

This likely has bugs and whatnot at this stage, but it gets the concepts of changes needed out there for discussion.

Rationale

snowman2 · 2019-01-02T02:32:43Z

Current issues in CRS tests is the error:

proj_create_operations: Source and target ellipsoid do not belong to the same celestial body

snowman2 · 2019-03-26T21:34:54Z

Also, this will mean that python 2.7 won't work on windows due to c++11 requirement for Proj 6.0.0

dopplershift · 2019-04-02T19:58:31Z

I think we were already close to dropping 2.7, so this is probably as good a reason as any. Might want to have one more release before we merge this...but then we'd have to be careful about what proj C library is used to build. Ick. @pelson ?

snowman2 · 2019-04-02T20:08:47Z

I wouldn't recommend merging this just yet. It was created before 6.0.0 was released in preparation for the release and the API has changed since then.

setup.py

snowman2 · 2019-04-10T01:21:36Z

Well, at least the errors I mentioned earlier are showing in the build now :)

snowman2 · 2019-06-15T02:43:49Z

I see a lot of failures due to the Source and target ellipsoid do not belong to the same celestial body error.

More information about this issue:

Essentially, the tests are using invalid transformations in multiple places if I understand correctly.

stickler-ci · 2019-06-15T18:36:39Z

lib/cartopy/crs.py

@@ -1188,7 +1188,7 @@ def __init__(self, central_longitude=-96.0, central_latitude=39.0,
            lons[1:-1] = np.linspace(central_longitude - 180 + 0.001,
                                     central_longitude + 180 - 0.001, n)

-        points = self.transform_points(PlateCarree(), lons, lats)
+        points = self.transform_points(PlateCarree(globe=self.globe), lons, lats)


E501 line too long (81 > 79 characters)

stickler-ci · 2019-06-15T18:36:39Z

lib/cartopy/crs.py

@@ -1266,7 +1266,7 @@ def __init__(self, central_longitude=0.0, central_latitude=0.0,
        lon = central_longitude + 180
        sign = np.sign(central_latitude) or 1
        lat = -central_latitude + sign * 0.01
-        x, max_y = self.transform_point(lon, lat, PlateCarree())
+        x, max_y = self.transform_point(lon, lat, PlateCarree(globe=self.globe))


E501 line too long (80 > 79 characters)

stickler-ci · 2019-06-15T18:36:40Z

lib/cartopy/tests/test_crs.py

@@ -190,8 +190,8 @@ def test_globe(self):
        rugby_moll = ccrs.Mollweide(globe=rugby_globe)
        footy_moll = ccrs.Mollweide(globe=footy_globe)

-        rugby_pt = rugby_moll.transform_point(10, 10, ccrs.Geodetic())
-        footy_pt = footy_moll.transform_point(10, 10, ccrs.Geodetic())
+        rugby_pt = rugby_moll.transform_point(10, 10, ccrs.Geodetic(globe=rugby_globe))


E501 line too long (87 > 79 characters)

stickler-ci · 2019-06-15T18:36:40Z

lib/cartopy/tests/test_crs.py

-        rugby_pt = rugby_moll.transform_point(10, 10, ccrs.Geodetic())
-        footy_pt = footy_moll.transform_point(10, 10, ccrs.Geodetic())
+        rugby_pt = rugby_moll.transform_point(10, 10, ccrs.Geodetic(globe=rugby_globe))
+        footy_pt = footy_moll.transform_point(10, 10, ccrs.Geodetic(globe=footy_globe))


E501 line too long (87 > 79 characters)

stickler-ci · 2019-06-15T18:51:34Z

lib/cartopy/mpl/geoaxes.py

@@ -504,7 +504,7 @@ def format_coord(self, x, y):
        A string formatted for the Matplotlib GUI status bar.

        """
-        lon, lat = ccrs.Geodetic().transform_point(x, y, self.projection)
+        lon, lat = ccrs.Geodetic(self.projection.globe).transform_point(x, y, self.projection)


E501 line too long (94 > 79 characters)

stickler-ci · 2019-06-15T18:51:34Z

lib/cartopy/mpl/geoaxes.py

@@ -583,7 +583,7 @@ def tissot(self, rad_km=500, lons=None, lats=None, n_samples=80, **kwargs):
                                     n_samples=n_samples)
                geoms.append(sgeom.Polygon(circle))

-        feature = cartopy.feature.ShapelyFeature(geoms, ccrs.Geodetic(),
+        feature = cartopy.feature.ShapelyFeature(geoms, ccrs.Geodetic(self.projection.globe),


E501 line too long (93 > 79 characters)

snowman2 · 2019-06-22T16:36:35Z

Question for @pelson @dopplershift @QuLogic
Do y'all know the reasoning behind the logic for the default globe for PlateCaree?

cartopy/lib/cartopy/crs.py

Line 705 in 1942c7b

globe = Globe(semimajor_axis=math.degrees(1))

>>> from cartopy.crs import PlateCarree
>>> pc = PlateCarree()
>>> pc.proj4_init
'+proj=eqc +ellps=WGS84 +a=57.29577951308232 +lon_0=0.0 +no_defs'

The semimajor_axis varies quite a bit from any other value I have seen.

Also, from what I can tell, it seems that meters are the units expected for the semi major axis:

>>> from pyproj import CRS
>>> crs = CRS('+proj=eqc +ellps=WGS84 +a=57.29577951308232 +lon_0=0.0 +no_defs')
>>> crs.ellipsoid
ELLIPSOID["unknown",57.2957795130823,298.257223563,
    LENGTHUNIT["metre",1,
        ID["EPSG",9001]]]
>>> crs.ellipsoid.semi_major_metre
57.29577951308232

snowman2 · 2019-06-23T03:41:52Z

Another data point on the plate carree ellipsoid base on https://proj.org/operations/projections/eqc.html:

>>> from pyproj import CRS
>>> cc = CRS.from_epsg(32622)
>>> cc.ellipsoid
ELLIPSOID["WGS 84",6378137,298.257223563,
    LENGTHUNIT["metre",1],
    ID["EPSG",7030]]
>>> cc.ellipsoid.semi_major_metre
6378137.0
>>> ceqc = CRS("+proj=eqc +lat_ts=0")
>>> ceqc.ellipsoid
ELLIPSOID["WGS 84",6378137,298.257223563,
    LENGTHUNIT["metre",1],
    ID["EPSG",7030]]
>>> ceqc.ellipsoid.semi_major_metre
6378137.0

It seems 6378137.0 could be a good default?

dopplershift · 2019-06-24T15:22:07Z

@snowman2 That particular choice of ellipsoid as the default for PlateCarree is a ~~hack~~ clever solution to allow passing lats and lons as Cartesian coordinates to PlateCarree, which is really just an equirectangular projection. That choice of Globe also means you get unexpected behavior when changing it (i.e. it no longer takes lons/lats). See #709.

snowman2 · 2019-06-24T21:38:32Z

Thanks for the explanation - that make sense. Well, it seems this is no longer allowed in PROJ 6+, so it will need to be updated before upgrading.

Based on #1164, I think it would make sense to use latlon. In pyproj we default to assume all input is degrees unless you toggle the radians flag and do conversions accordingly as needed by PROJ:
https://github.com/pyproj4/pyproj/blob/cecbdf4a516bf031c6e8fab0cf7188148dafc9f4/pyproj/_transformer.pyx#L164-L176

Is this something you would be interested in?

dopplershift · 2019-07-05T21:57:03Z

@snowman2 I think what we need is:

Make a new lat/lon projection that takes degrees
Add an EquidistantCylindrical projection that works like everything else with regards to globes
Deprecate PlateCarree, or at least its current behavior

snowman2 · 2019-07-06T00:57:35Z

@dopplershift, I think something just clicked in my brain. Is the goal to create something that converts from the "WGS84" or "EPGS:4326" to a global projected coordinate system? Or to convert from the geodetic CRS to the projected CRS. Either way, I think a new base class is needed. This class would be similar to the pyproj.Transformer, however it would default to have the from_crs always be either "WGS84" or the geodetic CRS based on the projected CRS depending on what you want (See: http://pyproj4.github.io/pyproj/stable/gotchas.html#proj-not-a-generic-latitude-longitude-to-projection-converter). This would enable the globe parameter to be supported as well open up the option for users to use additional Transformer classes that convert from latlon to a projected coordinate system.

snowman2 · 2019-07-06T01:03:14Z

An idea of different global projected coordinate systems could include:
EPSG:3857 (Pseudo web mercator)
EPSG:3395 "WGS 84 / World Mercator"

Ideas from: https://lists.osgeo.org/pipermail/proj/2019-June/008653.html

snowman2 · 2020-02-22T04:22:07Z

Currently upgrading to use the proj.h API in PROJ 6+ (an soon 7) has many changes/challenges. @dopplershift has expressed interest in potentially using pyproj 2 itself within cartopy to replace the direct need for building against the proj.h API. Is this something that the cartopy project is interested in?

greglucas · 2020-02-23T02:06:33Z

I'm 👍 on using pyproj2, since you've already built in all of the new Transformer hooks. Let's see how others feel about this too though. Would this remove the need for Cartopy to use pyepsg too? There was a bit of a hiccup recently when epsg.io went down and not depending on an external website would be nice.

Cartopy is currently still supporting some pretty old Python versions, so we would have to drop some older Python versions to make this work it looks like.

I think that all of this should actually be thought about from a broader perspective of what packages should handle what operations in a future big release. It looks like pygeos and Shapely will be merging their GEOS library work together in the (hopefully not too distant) future. There was a discussion about moving the GEOS optimizations out of Cartopy. Maybe this goes in parallel with that update to start moving some of the Cartopy Cython optimization code into other upstream libraries where it makes sense. (i.e. code in trace.pyx to shapely/pygeos, and _crs.pyx into pyproj2)

snowman2 · 2020-02-23T02:45:35Z

Let's see how others feel about this too though.

Should I open up a separate issue?

Would this remove the need for Cartopy to use pyepsg too?

Yes, it will remove that.

dopplershift · 2020-02-24T18:26:45Z

@snowman2 A separate issue might make sense, since we're veering off the topic of this PR. I'll go ahead and open it with my thoughts.

dopplershift · 2020-02-24T18:27:23Z

See #1477.

snowman2 · 2020-02-25T20:15:31Z

Going to close in favor of #1477.

SciTools-assistant added the Blocked: CLA needed See https://scitools.org.uk. Submit the form at: https://scitools.org.uk/cla/v4/form label Dec 31, 2018

snowman2 force-pushed the proj6 branch 3 times, most recently from 28fba75 to 6dbff9a Compare January 2, 2019 02:24

pelson added Type: Enhancement Experience-needed: high Component: proj SemVer: major labels Jan 2, 2019

snowman2 closed this Mar 26, 2019

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initial concepts for updating to PROJ 6+

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begin to address the celestial body errors

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adamjstewart mentioned this pull request Jun 17, 2019

py-cartopy does not yet support PROJ.6 spack/spack#11765

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snowman2 mentioned this pull request Jan 14, 2020

Error to_crs : ellipsoid do not belong to the same celestial body geopandas/geopandas#1264

Closed

dopplershift mentioned this pull request Feb 24, 2020

Port to use pyproj v2 #1477

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snowman2 closed this Feb 25, 2020

snowman2 mentioned this pull request Aug 26, 2020

Ensure consistent globe radius (PlateCarree) #1644

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3 tasks

snowman2 changed the title ~~WIP: updating to proj.4 6.0.0~~ WIP: Updating to PROJ 6+ proj.h C API Jun 23, 2021

snowman2 mentioned this pull request Jun 24, 2021

REF: Use pyproj 3+ for PROJ 8+ migration #1808

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bjlittle mentioned this pull request Sep 21, 2021

Support cartopy 0.20 and proj 8.1.0 SciTools/iris#4331

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knutfrode mentioned this pull request Oct 15, 2021

remove cartopy<0.20 requirement OpenDrift/opendrift#733

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WIP: Updating to PROJ 6+ proj.h C API #1252

WIP: Updating to PROJ 6+ proj.h C API #1252

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WIP: Updating to PROJ 6+ proj.h C API #1252

WIP: Updating to PROJ 6+ proj.h C API #1252

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Rationale

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