{"action":"created","issue":{"url":"https://api.github.com/repos/proj4-bot/proj.4/issues/197","labels_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/197/labels{/name}","comments_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/197/comments","events_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/197/events","html_url":"https://github.com/proj4-bot/proj.4/issues/197","id":79337097,"number":197,"title":"invgeod gives incorrect results for nearly antipodal points + FIX","user":{"login":"proj4-bot","id":12542084,"avatar_url":"https://avatars.githubusercontent.com/u/12542084?v=3","gravatar_id":"","url":"https://api.github.com/users/proj4-bot","html_url":"https://github.com/proj4-bot","followers_url":"https://api.github.com/users/proj4-bot/followers","following_url":"https://api.github.com/users/proj4-bot/following{/other_user}","gists_url":"https://api.github.com/users/proj4-bot/gists{/gist_id}","starred_url":"https://api.github.com/users/proj4-bot/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/proj4-bot/subscriptions","organizations_url":"https://api.github.com/users/proj4-bot/orgs","repos_url":"https://api.github.com/users/proj4-bot/repos","events_url":"https://api.github.com/users/proj4-bot/events{/privacy}","received_events_url":"https://api.github.com/users/proj4-bot/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/proj4-bot/proj.4/labels/bug","name":"bug","color":"fc2929"},{"url":"https://api.github.com/repos/proj4-bot/proj.4/labels/C:%20CommandlineUtilities","name":"C: CommandlineUtilities","color":"0000aa"},{"url":"https://api.github.com/repos/proj4-bot/proj.4/labels/P:%20major","name":"P: major","color":"f6f6f6"}],"state":"closed","locked":false,"assignee":null,"milestone":null,"comments":12,"created_at":"2015-05-22T07:42:26Z","updated_at":"2015-05-22T07:42:57Z","closed_at":"2015-05-22T07:42:51Z","body":"**Reported by karney on 30 Nov 2012 17:00 UTC**\ninvgeod gives incorrect results for nearly antipodal points,\r\ne.g.,\r\n  echo -30 0 29.9 179.9 | invgeod +ellps=WGS84\r\ngives\r\n  104d58'28.075\"  -105d11'13.983\" 19978869.258\r\n\r\nYou can verify that this is incorrect by solving the resulting\r\ndirect geodesic problem.  Of course, this is an old-standing\r\nbug, but no-one seems to have had the energy to fix it.  The web\r\npage\r\n\r\n  http://trac.osgeo.org/proj/wiki/GeodesicCalculations\r\n\r\nweakly says \"But it is probably good enough for most\r\napplications.\"\r\n\r\nI've recently transcribed the geodesic routines in GeographicLib\r\ninto C.  This enables geod and invgeod to be patched so that\r\n\r\n  * the results are accurate to round off for |f| < 1/50\r\n  * the inverse solution always converges\r\n\r\nI attach a patch which can be applied to proj-4.8.0, via\r\n\r\n  cd proj-4.8.0\r\n  gunzip < proj-4.8.0-geodesic.patch.gz | patch -p1\r\n\r\nNote that this patches Makefile.in as well as Makefile.am.  But\r\npresumably Makefile.in is created by the autogen process when\r\nyou make a release.\r\n\r\nLet me know if you have any questions\n\nMigrated-From: https://trac.osgeo.org/proj/ticket/197"},"comment":{"url":"https://api.github.com/repos/proj4-bot/proj.4/issues/comments/104553543","html_url":"https://github.com/proj4-bot/proj.4/issues/197#issuecomment-104553543","issue_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/197","id":104553543,"user":{"login":"proj4-bot","id":12542084,"avatar_url":"https://avatars.githubusercontent.com/u/12542084?v=3","gravatar_id":"","url":"https://api.github.com/users/proj4-bot","html_url":"https://github.com/proj4-bot","followers_url":"https://api.github.com/users/proj4-bot/followers","following_url":"https://api.github.com/users/proj4-bot/following{/other_user}","gists_url":"https://api.github.com/users/proj4-bot/gists{/gist_id}","starred_url":"https://api.github.com/users/proj4-bot/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/proj4-bot/subscriptions","organizations_url":"https://api.github.com/users/proj4-bot/orgs","repos_url":"https://api.github.com/users/proj4-bot/repos","events_url":"https://api.github.com/users/proj4-bot/events{/privacy}","received_events_url":"https://api.github.com/users/proj4-bot/received_events","type":"User","site_admin":false},"created_at":"2015-05-22T07:42:57Z","updated_at":"2015-05-22T07:42:57Z","body":"**Attachment added by karney on 11 Dec 2012 14:02 UTC**\nhttps://trac.osgeo.org/proj/attachment/ticket/197/geodesic.c"}}