{"action":"opened","issue":{"url":"https://api.github.com/repos/OSGeo/proj.4/issues/881","repository_url":"https://api.github.com/repos/OSGeo/proj.4","labels_url":"https://api.github.com/repos/OSGeo/proj.4/issues/881/labels{/name}","comments_url":"https://api.github.com/repos/OSGeo/proj.4/issues/881/comments","events_url":"https://api.github.com/repos/OSGeo/proj.4/issues/881/events","html_url":"https://github.com/OSGeo/proj.4/issues/881","id":307103863,"number":881,"title":"+towgs84=0,0,0 ignored in pipelines","user":{"login":"rouault","id":1192433,"avatar_url":"https://avatars2.githubusercontent.com/u/1192433?v=4","gravatar_id":"","url":"https://api.github.com/users/rouault","html_url":"https://github.com/rouault","followers_url":"https://api.github.com/users/rouault/followers","following_url":"https://api.github.com/users/rouault/following{/other_user}","gists_url":"https://api.github.com/users/rouault/gists{/gist_id}","starred_url":"https://api.github.com/users/rouault/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rouault/subscriptions","organizations_url":"https://api.github.com/users/rouault/orgs","repos_url":"https://api.github.com/users/rouault/repos","events_url":"https://api.github.com/users/rouault/events{/privacy}","received_events_url":"https://api.github.com/users/rouault/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":0,"created_at":"2018-03-21T02:45:13Z","updated_at":"2018-03-21T02:45:13Z","closed_at":null,"author_association":"OWNER","body":"With proj master\r\n```\r\necho \"440720 3751320 0\" |  src/cct +proj=pipeline +step +proj=utm +zone=11 +ellps=clrk66 +towgs84=0,0,0 +inv +step +proj=utm +zone=11 +datum=WGS84\r\n   440721.3314   3751514.1319        0.0000           inf\r\n```\r\nwhereas the equivalent cs2cs gives 440719.958709357 3751294.2109841 -4.44340920541435\r\n\r\nIf you slightly modify the towgs84 values to be almost 0 like\r\n```\r\necho \"440720 3751320 0\" |  src/cct +proj=pipeline +step +proj=utm +zone=11 +ellps=clrk66 +towgs84=0.000000000001,0,0 +inv +step +proj=utm +zone=11 +datum=WGS84\r\n   440721.3314   3751514.1319        0.0000           inf\r\n```\r\nyou get the expected result. This strong discontinuity in outputs regarding very slight input parameter changes is not expected from my point of view.\r\n\r\nThe reason is that the completely 0 towgs84 is ignored in cs2cs_emulation_setup(), and so no cartesian/geodetic transformations are done to change the ellipsoids.\r\n\r\nSuggested fix to come in a pull request"}}
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