{"id":1792,"date":"2009-06-04T23:38:49","date_gmt":"2009-06-04T23:38:49","guid":{"rendered":"http:\/\/justthesam.com\/2009\/06\/iphone-dev-gps-vs-cell-triangulation-vs-wifi\/"},"modified":"2009-06-04T23:38:49","modified_gmt":"2009-06-04T23:38:49","slug":"iphone-dev-gps-vs-cell-triangulation-vs-wifi","status":"publish","type":"post","link":"https:\/\/justthesam.com\/?p=1792","title":{"rendered":"iPhone Dev: GPS vs Cell Triangulation vs WiFi"},"content":{"rendered":"<div>I&#39;ve been working on an iPhone app that uses location data extensively. From poring through the raw data that comes from CLLocationManager I&#39;ve learned a few interesting things. In particular it seems that CLLocation objects with negative (i.e. invalid) verticalAccuracy value were likely derived from non-GPS sources &#8211; e.g. triangulation from cell towers or SkyHook WiFi positioning. In my app I really need only the purest, most accurate data so I&#39;m choosing to ignore non-GPS data and this is how I can tell it apart in order to do that.<\/div>\n<p><\/p>\n<div>It took a while for this realisation to dawn on me as I was seeing occasional poor data points mixed in with the good ones, and this seems to be because it occasionally slips in a non-GPS location in certain circumstances.<\/div>\n","protected":false},"excerpt":{"rendered":"<p>I&#39;ve been working on an iPhone app that uses location data extensively. From poring through the raw data that comes from CLLocationManager I&#39;ve learned a few interesting things. In particular it seems that CLLocation objects with negative (i.e. invalid) verticalAccuracy value were likely derived from non-GPS sources &#8211; e.g. triangulation from cell towers or SkyHook [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[16,22,33],"tags":[],"class_list":["post-1792","post","type-post","status-publish","format-standard","hentry","category-mac","category-programming","category-webtech"],"_links":{"self":[{"href":"https:\/\/justthesam.com\/index.php?rest_route=\/wp\/v2\/posts\/1792","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/justthesam.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/justthesam.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/justthesam.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/justthesam.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1792"}],"version-history":[{"count":0,"href":"https:\/\/justthesam.com\/index.php?rest_route=\/wp\/v2\/posts\/1792\/revisions"}],"wp:attachment":[{"href":"https:\/\/justthesam.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1792"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/justthesam.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1792"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/justthesam.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1792"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}