{"action":"created","issue":{"url":"https://api.github.com/repos/proj4-bot/proj.4/issues/36","labels_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/36/labels{/name}","comments_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/36/comments","events_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/36/events","html_url":"https://github.com/proj4-bot/proj.4/issues/36","id":79314486,"number":36,"title":"tmerc \"back folding\" problems.","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:%20Core","name":"C: Core","color":"0000aa"},{"url":"https://api.github.com/repos/proj4-bot/proj.4/labels/P:%20major","name":"P: major","color":"f6f6f6"}],"state":"open","locked":false,"assignee":null,"milestone":{"url":"https://api.github.com/repos/proj4-bot/proj.4/milestones/2","html_url":"https://github.com/proj4-bot/proj.4/milestones/4.7.0","labels_url":"https://api.github.com/repos/proj4-bot/proj.4/milestones/2/labels","id":1124794,"number":2,"title":"4.7.0","description":"None","creator":{"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},"open_issues":4,"closed_issues":0,"state":"closed","created_at":"2015-05-22T06:06:01Z","updated_at":"2015-05-22T06:26:41Z","due_on":"1970-01-01T00:00:00Z","closed_at":"2015-05-22T06:06:01Z"},"comments":2,"created_at":"2015-05-22T06:26:41Z","updated_at":"2015-05-22T06:26:47Z","closed_at":null,"body":"**Reported by warmerdam on 17 Jun 2008 15:46 UTC**\nYou can demonstrate the problem with the PROJ.4 commandline program cs2cs:\r\n\r\n```\r\ncs2cs +proj=latlong +datum=WGS84 +to +proj=utm +zone=32 +datum=WGS84\r\n```\r\n\r\nGive as input, this point in Alaska:\r\n```\r\n-149.66 64.237\r\n```\r\nAnd you get this:\r\n```\r\n522986.92       5029096.80 0.00\r\n```\r\nwhich is somewhere in Italy (near Milan). \r\n\r\nI realize this result is an effect of using tmerc equations far from where they are valid, but it causes serious problems in MapServer when trying to establish which images intersect a target map request.  In this case we have images from around the world, some in relatively local projections like tmerc. We reproject the map request bounds into the target projection and check for overlap. \r\n\r\nWhat I would like is if we could make the tmerc projection fail (ie return HUGE_VAL) for points so far from the central meridian that they are likely to start folding back on themselves. \n\nMigrated-From: https://trac.osgeo.org/proj/ticket/5"},"comment":{"url":"https://api.github.com/repos/proj4-bot/proj.4/issues/comments/104536478","html_url":"https://github.com/proj4-bot/proj.4/issues/36#issuecomment-104536478","issue_url":"https://api.github.com/repos/proj4-bot/proj.4/issues/36","id":104536478,"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":"2015-05-22T06:26:47Z","updated_at":"2015-05-22T06:26:47Z","body":"**Comment by warmerdam on 18 Jun 2008 01:16 UTC**\nGerald I. Evenden wrote:\r\n> etmerc has one limit level which is only a few degrees from del-lambda=90.  The original code had several \"levels\" of error of with different return codes but because there was not anyway to do this multilevel return in libproj4 I just used the one at the furthest extent.\r\n\r\nGerald,\r\n\r\nI'm not sure what you mean above.  I looked through the code for transverse\r\nmercator in PROJ.4, and libproj4 and I don't observe any obvious limit\r\nlogic on lam or y.\r\n\r\n> But the method of establishing a limit would appear to be done on the basis of Easting rather than a cutoff due to a lat-lon limit check.  Perhaps do the calculation regarless of geographic coordinates and then reject based upon easting greater than a percentage of a or R or, of course, equation failure.\r\n\r\nI can understand this, but the problem is that the lon/lat to\r\nprojected conversion is giving a plausible location near the\r\ncentral meridian in TM projected coordinates even though the\r\nlon/lat location was very very far from the central meridian.\r\nSo I don't see how checking the easting after reprojection is\r\ngoing to be sufficient.\r\n\r\nSee:\r\n  http://trac.osgeo.org/proj/ticket/5\r\n\r\n> On inverse projection just reject if |easting| too large.\r\n>\r\n> Allow an override option for those who want to play around.  ;-)\r\n\r\nI have taken the liberty of adding you as a cc: on the ticket.\r\nIf you are interested in adding notes in the ticket, you would need\r\nto create an OSGeo login at:\r\n\r\n  https://www.osgeo.org/cgi-bin/ldap_create_user.py\r\n\r\nand then login using that.\r\n\r\nI'm going to do a preliminary hack, but I'm hoping you will\r\nconsider applying a more generalized/good solution upstream in\r\nlibproj4. 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