Drawing an inset map in a separate axes sometimes causes "RuntimeError: Unidentified problem with geometry, linestring being re-added."

[mhearne-usgs]

Platform: Mac OS 10.10.5
Python: 3.6.0 | packaged by conda-forge | (default, Feb 10 2017, 07:08:35)
Cartopy Version: 0.15.0

Below is a script that causes the error: "Unidentified problem with geometry, linestring being re-added." in crs.py.

Notice that there are other regions (I've included one) in the world where drawing this inset map does NOT cause this error.

#!/usr/bin/env python

import numpy as np
import matplotlib.pyplot as plt
import cartopy
import cartopy.crs as ccrs  # projections

WATERCOLOR = '#7AA1DA'

#This region in the phillipines causes no errors
#xmin,xmax,ymin,ymax = (122.460700,128.460700,6.967600,12.877600)

#this region in india causes an error
xmin,xmax,ymin,ymax = (90.6505, 96.6505, 22.080346634631709, 27.526853365368289)


clon = (xmin + xmax)/2
clat = (ymin + ymax)/2
width = (xmax-xmin)*np.cos(np.radians(clat))*111.191
height = (ymax-ymin)*111.191
aspect = width/height
FIGWIDTH = 7.0
figheight = FIGWIDTH/aspect
bbox = (xmin,ymin,xmax,ymax)
bounds = (xmin,xmax,ymin,ymax)
figsize = (FIGWIDTH,figheight)

proj = ccrs.Mercator(central_longitude=clon,
                     min_latitude=ymin,
                     max_latitude=ymax,
                     globe=None)
geoproj = ccrs.PlateCarree()

figure = plt.figure(figsize=figsize)
ax = figure.add_axes([0,0,1,1],projection=proj)
ax.set_extent([xmin, xmax, ymin, ymax],crs=geoproj)

#normally I would do interesting things here, but they're not germane to 
#reproducing the problem

corner_rect = (0.84999999999999987,
               0.012441587723185982,
               0.14000000000000001,
               0.13930240350766115)

clat2 = round(clat)
clon2 = round(clon)

#draw a little globe in the corner showing in small-scale where the earthquake is located.
proj = ccrs.Orthographic(central_latitude=clat2,
                         central_longitude=clon2)

ax2 = figure.add_axes(corner_rect,projection=proj)

#in at least one area in the world (India), this raises an exception once you draw or save
ax2.add_feature(cartopy.feature.OCEAN, zorder=0,facecolor=WATERCOLOR,edgecolor=WATERCOLOR)

plt.savefig('test.png')

[mhearne-usgs]

If there is a work-around for this, I'd be happy to hear about that! :)

[mhearne-usgs]

@ajdawson I hate to single you out specifically on this, but I notice you've responded to a couple of other issues since mine, and I thought perhaps you would have some guidance on my issue. If you look at my example, I'm not actually trying to render any of my own datasets, just the ocean feature that comes with Cartopy. It seems to me that this is kind of a problem for the project - is there a particular person who is best suited to address this sort of issue?

[dopplershift]

I can say that this script reproduces the problem for me on osx, Python 3.6, cartopy 0.14.3 from conda-forge.

[ajdawson]

This looks like a transform problem, we have seen these here and there, but I don't know what is wrong specifically. You probably want the assistance of @pelson or @QuLogic

[mhearne-usgs]

@pelson @QuLogic Is this an issue that either of you have any guidance on? As I pointed out above, it's not a problem with data that I am introducing, but data that comes with Cartopy.

[marqh]

this is a problem and i'd like to get it fixed. there are other open issues regarding line string adding

@mhearne-usgs if you fancy giving me a head start, you could look into writing a test inside cartopy.tests which fails in this way, based on your example

i'll try to get onto looking at this as soon as i can

[mhearne-usgs]

@marqh I've forked cartopy, and have added a test. Looked at documentation on contributing and can't find any specific guidance there on how to set up my system for development or running tests.

[marqh]

hi @mhearne-usgs

i have not looked into this in detail yet

I use conda to establish test environments, you can look in the .travis.yml for clues, it is a small par tof what that file does

there are continuous integration tests running on this repository, so you can just write what looks like a sensible test case, and include it in one of the test modules, for example:
https://github.com/SciTools/cartopy/blob/master/lib/cartopy/tests/crs/test_mercator.py
as a new test function. if you propose this as a PR, the nice folks at travis will run the tests and report on your test case for us

[QuLogic]

Fixed by #974.