{"action":"opened","issue":{"url":"https://api.github.com/repos/ioam/geoviews/issues/38","repository_url":"https://api.github.com/repos/ioam/geoviews","labels_url":"https://api.github.com/repos/ioam/geoviews/issues/38/labels{/name}","comments_url":"https://api.github.com/repos/ioam/geoviews/issues/38/comments","events_url":"https://api.github.com/repos/ioam/geoviews/issues/38/events","html_url":"https://github.com/ioam/geoviews/issues/38","id":178672965,"number":38,"title":"Great-circle paths","user":{"login":"jbednar","id":1695496,"avatar_url":"https://avatars.githubusercontent.com/u/1695496?v=3","gravatar_id":"","url":"https://api.github.com/users/jbednar","html_url":"https://github.com/jbednar","followers_url":"https://api.github.com/users/jbednar/followers","following_url":"https://api.github.com/users/jbednar/following{/other_user}","gists_url":"https://api.github.com/users/jbednar/gists{/gist_id}","starred_url":"https://api.github.com/users/jbednar/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/jbednar/subscriptions","organizations_url":"https://api.github.com/users/jbednar/orgs","repos_url":"https://api.github.com/users/jbednar/repos","events_url":"https://api.github.com/users/jbednar/events{/privacy}","received_events_url":"https://api.github.com/users/jbednar/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2016-09-22T17:34:24Z","updated_at":"2016-09-22T17:34:24Z","closed_at":null,"body":"HLine and VLine will always be straight in screen coordinates, but it's important to be able to draw paths between two points that follow the great-circle path that one would need to travel in the real world.  Such paths can already be plotted using the latest geoviews master (thanks @philippjfr!):\r\n\r\n![image](https://cloud.githubusercontent.com/assets/1695496/18759031/3b64bd1a-80c0-11e6-9c66-48f387e440c7.png)\r\n\r\nthough it would be nice to increase the number of points to make smoother curves.  Philipp also had a suggestion for exposing the coordinate transformations for when you want to work with them explicitly:\r\n\r\n```python\r\n\r\npath = gv.Path([[(132, -0.08), (43.17, 51.53)]], crs=crs.Geodetic())\r\nmercator_path = GeoConversion(path, crs=crs.GOOGLE_MERCATOR)\r\n```\r\n\r\nThis all sounds good, but there are some other things that would help when working with great-circle paths.  First, if there is a function in cartopy or proj4 for computing a great-circle distance between two points, it would be great to show that in an example in a GeoViews tutorial, along with the above example of plotting paths.  Second, if there is not currently such a function, Philipp has some code of his own for computing it, and it would be good to add that to GeoViews so that people can work naturally with great-circle paths."}}
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