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Forum Index : Microcontroller and PC projects : Accuracy of Mobile Phone GPS & Google
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| Ray B Senior Member  Joined: 16/02/2007 Location: AustraliaPosts: 219 |
Recently I completed an evaluation of the accuracy of a GPS in a new smart phone and compared that to a Geoscience Australia GPS Antenna on Cocos Islands with an accuracy of +/- 1cm. I then compared accuracy to what is found in Google Earth. Original 3 page Word document was attempted to be published in PDF format (1.2MB)but for some reason the file uploaded does not seem to like PDF files > approx 400KB so it has now been published as 4 separate pages as follows: 2012-05-13_214238_HOW_ACCURATE_IS_GOOGLE_EARTH_Page1a.pdf 2012-05-13_214416_HOW_ACCURATE_IS_GOOGLE_EARTH_Page2.pdf 2012-05-13_215209_HOW_ACCURATE_IS_GOOGLE_EARTH_Page3a.pdf 2012-05-13_215235_HOW_ACCURATE_IS_GOOGLE_EARTH_Page4a.pdf RayB from Perth WA |
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| paceman Guru  Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Hi Ray, Interesting stuff - I did a quick double-take though when on page 2 you said, Now as Seconds are defined down to a resolution of 4 decimal places then latitude position can be determined down to 0.003072841 Metres or 0.03 of a millimetre. Plus / Minus the resolution & maybe other variables that I’m not aware of so it seems to me that GA can comfortably claim an accuracy of +/- 1cm or 10mm. A fast mental calculate of a 0.0001 secs in the 30 meters equivalent to 1 sec, makes the resolution 3 mm, not 0.03 mm. That makes the GA claim of +/- 5mm much more logical. Greg |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
2012-05-13_230801_HOW_ACCURATE_IS_GOOGLE_EARTH_&_PHONE_GPS.p df This is the full file from Ray. Ray would you believe it uploaded OK for me  . So I'm guesing it was a script timeout error. If a page takes too long to process, the server will time out the page and return a error. That file upload page has error trapping, and gives a generic error message, which may be wrong. As my computer and the server are on the same network, it uploaded instantly for me, but for you, there may have been a slow down somewhere on the internet and the server got tired of waiting for the file to upload.
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Ray B Senior Member Joined: 16/02/2007 Location: AustraliaPosts: 219 |
Yes Greg that does make more sense with 3mm. When I did my initial calc that was the value I worked out about a week or so ago but my scribbled notes caused this obvious error. Bottom line of the article is so people can understand the accuracy of some of the gear out there in the commercial world, let alone what military or organisations like NASA must be achieving and for what purpose. Perhaps some other readers may have some experience with other GPS devices especially with what accuracy is being achieved when interfacing microcontrollers. Some of the earth movement data from http://192.104.43.25/status/solutions/analysis.html looks interesting & appears to be downloadable not that I can immediately see a purpose for my own use. Good to see how some of our tax dollars is spent.  RayB from Perth WA |
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| paceman Guru Joined: 07/10/2011 Location: AustraliaPosts: 1329 |
Yes, makes you wonder how the USA manages to get "collateral damage" anymore these days, doesn't it? Six or seven years ago my mate installed a GPS marine navigation system on his boat. Our first foray (down at Schouten Is in Tasmania) showed our position on the installed map as being about half a kilometer up the mountain - didn't stop the flathead biting :-) Last Xmas we used Google Earth on a 3G iPad instead and hit our spot right on! Greg |
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