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25 lines
3.0 KiB
JSON
25 lines
3.0 KiB
JSON
{
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"date": "2024-07-21",
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"title": "Photo - Photo GPS is unreliable",
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"place": "Photo",
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"other_people": "",
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"text": "During this same trip walking to Geschandalm, later analysis of the GPS locations of various photos showed a lot of variability. \nThis is a particularly clear example where the location is obvious in the photo (it is definitely on the path) \nbut the GPS location stored by the phone camera is 60m away.\n<p>\nI had one phone (Xioami) continually tracking my location (using OSMand) which produced the GPX track, \nand another (Pixel) used for photographs. \nThe GPS data in the photos is clearly completely wrong for some of the photos - \npresumably because I hadn't left enough time for it to get a decent GPS fix before taking the photo. \nThis is particularly clear when there is a well-identified spot in the photo, \nsuch as this one right by the shady cliff (photo EXIF GPS locations are orange dots):<br>\n<a href=\"/years/2024/images/bad-gps.jpg\">\n<img width=20% src=\"/years/2024/images/bad-gps.jpg\"></a> \n<a href='/years/2024/l/PXL_20240721_082604148.NIGHT.html'><img src='/years/2024/t/PXL_20240721_082604148.NIGHT.jpg' /></a> \n<p>\nThe lesson to take away from this is to always take TWO photos at any one position, and throw away the first one. \nThis will nearly always work for most people, and is sufficiently simple that even undergraduates can remember it.\nAdditionally, \n<ol><li>always continually record a GPS track on the phone you are using to take photos with - \nthough this is unfortunately not always reliable either, as the camera app tends to cache locations and doesn't always \nget a fresh one from the \"location\" module in the phone,\n<li>Take a screenshot of the <a href=\"https://github.com/barbeau/gpstest#readme\">GPStest</a> app showing current location and accuracy data. You can get it from F-Droid or Google Play Store. <br /><figure class=onright width=20><a href='https://github.com/barbeau/gpstest#readme'><img width=64px src='/handbook/computing/t/gpstest.jpg' /></a><a href='https://github.com/barbeau/gpstest#readme'> <img width=64px src='/handbook/computing/t/F-Droid_Logo_4.svg.jpg' /></a> \n</figure>\n</ol>\n</p>\n <br />\n<div class=\"text-box\">\n<a href=\"/handbook/computing/myphone.html\">Your phone on expo</a> - Do not select the \"high accuracy\" location setting on your phone<br />\n<a href=\"/handbook/essentials.html\">GPS essentials on the plateau</a> - Safety information<br />\n<a href=\"/logbookentry/2024-07-21/2024-07-21c\">Photo GPS</a> - Is unreliable unless you follow procedure (this page)<br />\n <a href=\"/handbook/survey/gps.htm_edit\">Locating Entrances</a> - expo recommended methods<br />\n</div>",
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"slug": "2024-07-21c",
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"time_underground": 0.0,
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"author": {
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"slug": "philip-sargent",
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"nickname": "Philip S.",
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"tu": 0.0
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},
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"trippersons": [
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{
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"slug": "philip-sargent",
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"nickname": "Philip S.",
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"tu": 0.0
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}
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],
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"expedition": {
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"year": "2024",
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"name": "CUCC expo 2024"
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}
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} |