Points not plotting correctly with Orthographic projection

[moonshoes87]

Description

I am trying to plot map points but am getting some strange failures with the transform. In my simple example, I am trying to plot 3 points but they are getting doubled.

Code to reproduce

import matplotlib.pyplot as plt
import cartopy.crs as ccrs

lons = [214.5, 2.7, 197.5]                                                                                               
lats = [35, 36, 37.]

ax = plt.axes(projection=ccrs.Orthographic(
    central_longitude=0,
    central_latitude=90))
# plot lat/lon points                                                                                                         
ax.plot(lons, lats, 'ro',
        transform=ccrs.Geodetic())
# plot north pole for reference                                                                                               
ax.plot([0], [90], 'b^',
        transform=ccrs.Geodetic())
# add coastlines for reference                                                                                                
ax.coastlines(resolution='50m')
ax.set_global()

plt.show()

Traceback

With 0.16.0, there is no traceback. With Cartopy-0.16.1.dev170-, I get this UserWarning:

/Users/nebula/anaconda3/lib/python3.6/site-packages/cartopy/crs.py:1476: UserWarning: The Orthographic projection in Proj between 5.0.0 and 5.1.0 incorrectly transforms points. Use this projection with caution.

Full environment definition

Operating system

OSX 10.13.6

Cartopy version

0.16.0/0.16.1

conda list

# packages in environment at /Users/nebula/anaconda3:
#
# Name                    Version                   Build  Channel
_ipyw_jlab_nb_ext_conf    0.1.0                    py36_0  
alabaster                 0.7.11                   py36_0  
anaconda                  custom           py36ha4fed55_0  
anaconda-client           1.7.2                    py36_0  
anaconda-navigator        1.9.2                    py36_0  
anaconda-project          0.8.2                    py36_0  
appdirs                   1.4.3            py36h28b3542_0  
appnope                   0.1.0            py36hf537a9a_0  
appscript                 1.0.1            py36h1de35cc_1  
asn1crypto                0.24.0                   py36_0  
asteval                   0.9.12             pyh24bf2e0_1    conda-forge
astroid                   2.0.4                    py36_0  
astropy                   3.0.4            py36h1de35cc_0  
atomicwrites              1.2.1                    py36_0  
attrs                     18.2.0           py36h28b3542_0  
automat                   0.7.0                    py36_0  
autopep8                  1.3.5                     <pip>
babel                     2.6.0                    py36_0  
backcall                  0.1.0                    py36_0  
backports                 1.0                      py36_1  
backports.lzma            0.0.13           py36hd0afa68_0  
backports.shutil_get_terminal_size 1.0.0                    py36_2  
beautifulsoup4            4.6.3                    py36_0  
bitarray                  0.8.3            py36h1de35cc_0  
blas                      1.0                         mkl  
bleach                    2.1.4                    py36_0  
blosc                     1.14.4               hd9629dc_0  
bokeh                     0.13.0                   py36_0  
boto                      2.49.0                   py36_0  
bottleneck                1.2.1            py36h1d22016_1  
bzip2                     1.0.6                h1de35cc_5  
ca-certificates           2018.03.07                    0  
cartopy                   0.16.0           py36h9263bd1_0  
certifi                   2018.10.15               py36_0  
cffi                      1.11.5           py36h6174b99_1  
chardet                   3.0.4                    py36_1  
click                     6.7              py36hec950be_0  
cloudpickle               0.5.5                    py36_0  
clyent                    1.2.2                    py36_1  
cmarkgfm                  0.4.2                     <pip>
colorama                  0.3.9            py36hd29a30c_0  
conda                     4.5.11                   py36_0  
conda-build               3.15.1                   py36_0  
conda-env                 2.6.0                         1  
conda-verify              3.1.0                    py36_0  
constantly                15.1.0           py36h28b3542_0  
contextlib2               0.5.5            py36hd66e5e7_0  
cryptography              2.3.1            py36hdbc3d79_0  
curl                      7.61.0               ha441bb4_0  
cycler                    0.10.0           py36hfc81398_0  
cython                    0.28.5           py36h0a44026_0  
cytoolz                   0.9.0.1          py36h1de35cc_1  
dask-core                 0.19.2                   py36_0  
datashape                 0.5.4                    py36_1  
dbus                      1.13.2               h760590f_1  
decorator                 4.3.0                    py36_0  
distributed               1.23.2                   py36_0  
docutils                  0.14             py36hbfde631_0  
entrypoints               0.2.3                    py36_2  
et_xmlfile                1.0.1            py36h1315bdc_0  
expat                     2.2.6                h0a44026_0  
fastcache                 1.0.2            py36h1de35cc_2  
filelock                  3.0.8                    py36_0  
flask                     1.0.2                    py36_1  
flask-cors                3.0.6                    py36_0  
freetype                  2.9.1                hb4e5f40_0  
future                    0.16.0                   py36_2  
geos                      3.6.2                h5470d99_2  
get_terminal_size         1.0.0                h7520d66_0  
gettext                   0.19.8.1             h15daf44_3  
gevent                    1.3.6            py36h1de35cc_0  
glib                      2.56.2               hd9629dc_0  
glob2                     0.6                      py36_0  
gmp                       6.1.2                hb37e062_1  
gmpy2                     2.0.8            py36h6ef4df4_2  
greenlet                  0.4.15           py36h1de35cc_0  
h5py                      2.8.0            py36h878fce3_3  
hdf5                      1.10.2               hfa1e0ec_1  
heapdict                  1.0.0                    py36_2  
html5lib                  1.0.1                    py36_0  
hyperlink                 18.0.0                   py36_0  
icu                       58.2                 h4b95b61_1  
idna                      2.7                      py36_0  
imageio                   2.4.1                    py36_0  
imagesize                 1.1.0                    py36_0  
incremental               17.5.0                   py36_0  
intel-openmp              2019.0                      118  
ipykernel                 4.10.0                   py36_0  
ipython                   6.5.0                    py36_0  
ipython_genutils          0.2.0            py36h241746c_0  
ipywidgets                7.4.1                    py36_0  
iscompatible              0.1.1                     <pip>
isort                     4.3.4                    py36_0  
itsdangerous              0.24                     py36_1  
jbig                      2.1                  h4d881f8_0  
jdcal                     1.4                      py36_0  
jedi                      0.12.1                   py36_0  
jinja2                    2.10                     py36_0  
jpeg                      9b                   he5867d9_2  
jsonschema                2.6.0            py36hb385e00_0  
jupyter                   1.0.0                    py36_7  
jupyter_client            5.2.3                    py36_0  
jupyter_console           5.2.0                    py36_1  
jupyter_core              4.4.0                    py36_0  
jupyterlab                0.34.9                   py36_0  
jupyterlab_launcher       0.13.1                   py36_0  
keyring                   13.2.1                   py36_0  
kiwisolver                1.0.1            py36h0a44026_0  
lazy-object-proxy         1.3.1            py36h1de35cc_2  
libcurl                   7.61.0               hf30b1f0_0  
libcxx                    4.0.1                h579ed51_0  
libcxxabi                 4.0.1                hebd6815_0  
libedit                   3.1.20170329         hb402a30_2  
libffi                    3.2.1                h475c297_4  
libgfortran               3.0.1                h93005f0_2  
libiconv                  1.15                 hdd342a3_7  
libopenblas               0.3.3                hdc02c5d_3  
libpng                    1.6.34               he12f830_0  
libsodium                 1.0.16               h3efe00b_0  
libssh2                   1.8.0                h322a93b_4  
libtiff                   4.0.9                hcb84e12_2  
libxml2                   2.9.8                hab757c2_1  
libxslt                   1.1.32               hb819dd2_0  
llvmlite                  0.24.0           py36hc454e04_0  
lmfit                     0.9.11             pyh24bf2e0_1    conda-forge
locket                    0.2.0            py36hca03003_1  
lxml                      4.2.5            py36hef8c89e_0  
lzo                       2.10                 h362108e_2  
markupsafe                1.0              py36h1de35cc_1  
matplotlib                2.2.3            py36h54f8f79_0  
mccabe                    0.6.1                    py36_1  
mistune                   0.8.3            py36h1de35cc_1  
mkl                       2019.0                      118  
mkl-service               1.1.2            py36h6b9c3cc_5  
mkl_fft                   1.0.6            py36hb8a8100_0  
mkl_random                1.0.1            py36h5d10147_1  
more-itertools            4.3.0                    py36_0  
mpc                       1.1.0                h6ef4df4_1  
mpfr                      4.0.1                h3018a27_3  
mpmath                    1.0.0                    py36_2  
msgpack-python            0.5.6            py36h04f5b5a_1  
multipledispatch          0.6.0                    py36_0  
navigator-updater         0.2.1                    py36_0  
nbconvert                 5.3.1                    py36_0  
nbformat                  4.4.0            py36h827af21_0  
ncurses                   6.1                  h0a44026_0  
networkx                  2.1                      py36_0  
nltk                      3.3.0                    py36_0  
nose                      1.3.7                    py36_2  
notebook                  5.6.0                    py36_0  
numba                     0.39.0           py36h6440ff4_0  
numexpr                   2.6.8            py36h1dc9127_0  
numpy                     1.15.2           py36h6a91979_0  
numpy-base                1.15.2           py36h8a80b8c_0  
numpydoc                  0.8.0                    py36_0  
olefile                   0.46                     py36_0  
openpyxl                  2.5.6                    py36_0  
openssl                   1.0.2p               h1de35cc_0  
owslib                    0.16.0                   py36_0  
packaging                 17.1                     py36_0  
pandas                    0.23.4           py36h6440ff4_0  
pandoc                    2.2.3.2                       0  
pandocfilters             1.4.2                    py36_1  
parso                     0.3.1                    py36_0  
partd                     0.3.8            py36hf5c4cb8_0  
path.py                   11.1.0                   py36_0  
pathlib2                  2.3.2                    py36_0  
pcre                      8.42                 h378b8a2_0  
pep8                      1.7.1                    py36_0  
pexpect                   4.6.0                    py36_0  
pickleshare               0.7.4            py36hf512f8e_0  
pillow                    5.2.0            py36hb68e598_0  
pip                       18.1                      <pip>
pip                       10.0.1                   py36_0  
pip                       10.0.1                    <pip>
pkginfo                   1.4.2                    py36_1  
pluggy                    0.7.1            py36h28b3542_0  
ply                       3.11                     py36_0  
proj4                     5.0.1                h1de35cc_0  
prometheus_client         0.3.1            py36h28b3542_0  
prompt_toolkit            1.0.15           py36haeda067_0  
psutil                    5.4.7            py36h1de35cc_0  
ptyprocess                0.6.0                    py36_0  
py                        1.6.0                    py36_0  
pyasn1                    0.4.4            py36h28b3542_0  
pyasn1-modules            0.2.2                    py36_0  
pycodestyle               2.4.0                    py36_0  
pycosat                   0.6.3            py36h1de35cc_0  
pycparser                 2.18                     py36_1  
pycrypto                  2.6.1            py36h1de35cc_9  
pycurl                    7.43.0.2         py36hdbc3d79_0  
pyepsg                    0.3.2                    py36_0  
pyflakes                  2.0.0                    py36_0  
pygments                  2.2.0            py36h240cd3f_0  
pylint                    2.1.1                    py36_0  
pyodbc                    4.0.24           py36h0a44026_0  
pyopenssl                 18.0.0                   py36_0  
pyparsing                 2.2.0                    py36_1  
pyproj                    1.9.5.1          py36h833a5d7_1  
Pypubsub                  4.0.0                     <pip>
pyqt                      5.9.2            py36h655552a_2  
pyshp                     1.2.12                   py36_0  
pysocks                   1.6.8                    py36_0  
pytables                  3.4.4            py36h13cba08_0  
pytest                    3.8.0                    py36_0  
pytest-arraydiff          0.2              py36h39e3cac_0  
pytest-astropy            0.4.0                    py36_0  
pytest-doctestplus        0.1.3                    py36_0  
pytest-openfiles          0.3.0                    py36_0  
pytest-remotedata         0.3.0                    py36_0  
python                    3.6.6                hc167b69_0  
python-dateutil           2.7.3                    py36_0  
python.app                2                        py36_9  
pytz                      2018.5                   py36_0  
pywavelets                1.0.0            py36h1d22016_0  
pyyaml                    3.13             py36h1de35cc_0  
pyzmq                     17.1.2           py36h1de35cc_0  
qt                        5.9.6                h45cd832_2  
qtawesome                 0.4.4            py36h468c6fb_0  
qtconsole                 4.4.1                    py36_0  
qtpy                      1.5.0                    py36_0  
readline                  7.0                  h1de35cc_5  
readme-renderer           20.0                      <pip>
requests                  2.19.1                   py36_0  
requests-toolbelt         0.8.0                    py36_0  
rope                      0.11.0                   py36_0  
ruamel_yaml               0.15.46          py36h1de35cc_0  
scikit-learn              0.20.0           py36h4f467ca_1  
scipy                     1.1.0            py36h28f7352_1  
scripttest                1.3.0                      py_1    conda-forge
send2trash                1.5.0                    py36_0  
service_identity          17.0.0           py36h28b3542_0  
setuptools                39.0.1                    <pip>
setuptools                40.2.0                   py36_0  
setuptools                40.4.3                    <pip>
shapely                   1.6.4            py36h20de77a_0  
simplegeneric             0.8.1                    py36_2  
singledispatch            3.4.0.3          py36hf20db9d_0  
sip                       4.19.8           py36h0a44026_0  
six                       1.11.0                   py36_1  
six                       1.11.0                    <pip>
snappy                    1.1.7                he62c110_3  
snowballstemmer           1.2.1            py36h6c7b616_0  
sortedcollections         1.0.1                    py36_0  
sortedcontainers          2.0.5                    py36_0  
sphinx                    1.7.9                    py36_0  
sphinxcontrib             1.0                      py36_1  
sphinxcontrib-websupport  1.1.0                    py36_1  
spyder                    3.3.1                    py36_1  
spyder-kernels            0.2.6                    py36_0  
sqlalchemy                1.2.11           py36h1de35cc_0  
sqlite                    3.25.2               ha441bb4_0  
sympy                     1.2                      py36_0  
tblib                     1.3.2            py36hda67792_0  
terminado                 0.8.1                    py36_1  
testpath                  0.3.1            py36h625a49b_0  
tk                        8.6.8                ha441bb4_0  
toolz                     0.9.0                    py36_0  
tornado                   5.1              py36h1de35cc_0  
tqdm                      4.26.0           py36h28b3542_0  
traitlets                 4.3.2            py36h65bd3ce_0  
twine                     1.11.0                   py36_0  
twisted                   17.5.0                   py36_0  
typed-ast                 1.1.0            py36h1de35cc_0  
typing                    3.6.4                    py36_0  
uncertainties             3.0.2                    py36_1    conda-forge
unicodecsv                0.14.1           py36he531d66_0  
unixodbc                  2.3.7                h1de35cc_0  
urllib3                   1.23                     py36_0  
wcwidth                   0.1.7            py36h8c6ec74_0  
webencodings              0.5.1                    py36_1  
werkzeug                  0.14.1                   py36_0  
wheel                     0.31.1                   py36_0  
widgetsnbextension        3.4.1                    py36_0  
wrapt                     1.10.11          py36h1de35cc_2  
wxpython                  4.0.3            py36hebc47a7_0  
xlrd                      1.1.0                    py36_1  
xlsxwriter                1.1.0                    py36_0  
xlwings                   0.11.8                   py36_0  
xlwt                      1.2.0            py36h5ad1178_0  
xz                        5.2.4                h1de35cc_4  
yaml                      0.1.7                hc338f04_2  
zeromq                    4.2.5                h0a44026_1  
zict                      0.1.3                    py36_0  
zlib                      1.2.11               hf3cbc9b_2  
zope                      1.0                      py36_1  
zope.interface            4.5.0            py36h1de35cc_0  

pip list

Package                            Version    
---------------------------------- -----------
alabaster                          0.7.11     
anaconda-client                    1.7.2      
anaconda-navigator                 1.9.2      
anaconda-project                   0.8.2      
appdirs                            1.4.3      
appnope                            0.1.0      
appscript                          1.0.1      
asn1crypto                         0.24.0     
asteval                            0.9.12     
astroid                            2.0.4      
astropy                            3.0.4      
atomicwrites                       1.2.1      
attrs                              18.2.0     
Automat                            0.7.0      
autopep8                           1.3.5      
Babel                              2.6.0      
backcall                           0.1.0      
backports.lzma                     0.0.13     
backports.shutil-get-terminal-size 1.0.0      
beautifulsoup4                     4.6.3      
bitarray                           0.8.3      
bleach                             2.1.4      
bokeh                              0.13.0     
boto                               2.49.0     
Bottleneck                         1.2.1      
Cartopy                            0.16.0     
certifi                            2018.10.15 
cffi                               1.11.5     
chardet                            3.0.4      
click                              6.7        
cloudpickle                        0.5.5      
clyent                             1.2.2      
cmarkgfm                           0.4.2      
colorama                           0.3.9      
conda                              4.5.11     
conda-build                        3.15.1     
conda-verify                       3.1.0      
constantly                         15.1.0     
contextlib2                        0.5.5      
cryptography                       2.3.1      
cycler                             0.10.0     
Cython                             0.28.5     
cytoolz                            0.9.0.1    
dask                               0.19.2     
datashape                          0.5.4      
decorator                          4.3.0      
distributed                        1.23.2     
docutils                           0.14       
entrypoints                        0.2.3      
et-xmlfile                         1.0.1      
fastcache                          1.0.2      
filelock                           3.0.8      
Flask                              1.0.2      
Flask-Cors                         3.0.6      
future                             0.16.0     
gevent                             1.3.6      
glob2                              0.6        
gmpy2                              2.0.8      
greenlet                           0.4.15     
h5py                               2.8.0      
heapdict                           1.0.0      
html5lib                           1.0.1      
hyperlink                          18.0.0     
idna                               2.7        
imageio                            2.4.1      
imagesize                          1.1.0      
incremental                        17.5.0     
ipykernel                          4.10.0     
ipython                            6.5.0      
ipython-genutils                   0.2.0      
ipywidgets                         7.4.1      
iscompatible                       0.1.1      
isort                              4.3.4      
itsdangerous                       0.24       
jdcal                              1.4        
jedi                               0.12.1     
Jinja2                             2.10       
jsonschema                         2.6.0      
jupyter                            1.0.0      
jupyter-client                     5.2.3      
jupyter-console                    5.2.0      
jupyter-core                       4.4.0      
jupyterlab                         0.34.9     
jupyterlab-launcher                0.13.1     
keyring                            13.2.1     
kiwisolver                         1.0.1      
lazy-object-proxy                  1.3.1      
llvmlite                           0.24.0     
lmfit                              0.9.11     
locket                             0.2.0      
lxml                               4.2.5      
MarkupSafe                         1.0        
matplotlib                         2.2.3      
mccabe                             0.6.1      
mistune                            0.8.3      
mkl-fft                            1.0.6      
mkl-random                         1.0.1      
more-itertools                     4.3.0      
mpmath                             1.0.0      
msgpack                            0.5.6      
multipledispatch                   0.6.0      
navigator-updater                  0.2.1      
nbconvert                          5.3.1      
nbformat                           4.4.0      
networkx                           2.1        
nltk                               3.3        
nose                               1.3.7      
notebook                           5.6.0      
numba                              0.39.0     
numexpr                            2.6.8      
numpy                              1.15.2     
numpydoc                           0.8.0      
olefile                            0.46       
openpyxl                           2.5.6      
OWSLib                             0.16.0     
packaging                          17.1       
pandas                             0.23.4     
pandocfilters                      1.4.2      
parso                              0.3.1      
partd                              0.3.8      
path.py                            11.1.0     
pathlib2                           2.3.2      
pep8                               1.7.1      
pexpect                            4.6.0      
pickleshare                        0.7.4      
Pillow                             5.2.0      
pip                                18.1       
pkginfo                            1.4.2      
pluggy                             0.7.1      
ply                                3.11       
pmagpy                             4.2.7      
pmagpy-cli                         4.2.5      
prometheus-client                  0.3.1      
prompt-toolkit                     1.0.15     
psutil                             5.4.7      
ptyprocess                         0.6.0      
py                                 1.6.0      
pyasn1                             0.4.4      
pyasn1-modules                     0.2.2      
pycodestyle                        2.4.0      
pycosat                            0.6.3      
pycparser                          2.18       
pycrypto                           2.6.1      
pycurl                             7.43.0.2   
pyepsg                             0.3.2      
pyflakes                           2.0.0      
Pygments                           2.2.0      
pylint                             2.1.1      
pyodbc                             4.0.24     
pyOpenSSL                          18.0.0     
pyparsing                          2.2.0      
pyproj                             1.9.5.1    
Pypubsub                           4.0.0      
pyshp                              1.2.12     
PySocks                            1.6.8      
pytest                             3.8.0      
pytest-arraydiff                   0.2        
pytest-astropy                     0.4.0      
pytest-doctestplus                 0.1.3      
pytest-openfiles                   0.3.0      
pytest-remotedata                  0.3.0      
python-dateutil                    2.7.3      
pytz                               2018.5     
PyWavelets                         1.0.0      
PyYAML                             3.13       
pyzmq                              17.1.2     
QtAwesome                          0.4.4      
qtconsole                          4.4.1      
QtPy                               1.5.0      
readme-renderer                    20.0       
requests                           2.19.1     
requests-toolbelt                  0.8.0      
rope                               0.11.0     
ruamel-yaml                        0.15.46    
scikit-learn                       0.20.0     
scipy                              1.1.0      
scripttest                         1.3        
Send2Trash                         1.5.0      
service-identity                   17.0.0     
setuptools                         40.4.3     
Shapely                            1.6.4.post1
simplegeneric                      0.8.1      
singledispatch                     3.4.0.3    
six                                1.11.0     
snowballstemmer                    1.2.1      
sortedcollections                  1.0.1      
sortedcontainers                   2.0.5      
Sphinx                             1.7.9      
sphinxcontrib-websupport           1.1.0      
spyder                             3.3.1      
spyder-kernels                     0.2.6      
SQLAlchemy                         1.2.11     
sympy                              1.2        
tables                             3.4.4      
tblib                              1.3.2      
terminado                          0.8.1      
testpath                           0.3.1      
toolz                              0.9.0      
tornado                            5.1        
tqdm                               4.26.0     
traitlets                          4.3.2      
twine                              1.11.0     
Twisted                            17.5.0     
typed-ast                          1.1.0      
typing                             3.6.4      
uncertainties                      3.0.2      
unicodecsv                         0.14.1     
urllib3                            1.23       
wcwidth                            0.1.7      
webencodings                       0.5.1      
Werkzeug                           0.14.1     
wheel                              0.31.1     
widgetsnbextension                 3.4.1      
wrapt                              1.10.11    
wxPython                           4.0.3      
xlrd                               1.1.0      
XlsxWriter                         1.1.0      
xlwings                            0.11.8     
xlwt                               1.2.0      
zict                               0.1.3      
zope.interface                     4.5.0      

[QuLogic]

proj4 5.0.1 h1de35cc_0

Like the warning says, you are using a buggy version of Proj (at least for this projection.)

[moonshoes87]

@QuLogic, can you give any more hints?

I've tried downgrading to proj4==4.9.3 but the problem persists with no UserWarning. Downgrading to proj4<4.9.3 is incompatible with cartopy.

Likewise, if I upgrade to proj4==5.2.0 (via conda-forge), the problem persists again with no UserWarning.

Is there any known environment solution for orthographic projections?

[QuLogic]

It works for me with Matplotlib 3.0.1, broken with 2.2.3, so I guess you'd need to update that too.

[QuLogic]

Actually, that might not be it, but an easier fix is to use ax.scatter instead of ax.plot. With the latter, it is quite possible that Cartopy will attempt to interpolate the line, and you will get intermediate points, whereas you will not with the former. (I am not entirely sure if Matplotlib switches to just transforming points instead of lines when you scatter with ax.plot.)

[moonshoes87]

Thanks. Yes, it appears that using ax.scatter fixes the problem. https://stackoverflow.com/questions/53195551/cartopy-plotting-points-incorrectly-with-orthographic-projection