One of the other issues you need to look at is what you’re doing with the data and how valuable it is to you. if you’re surveying a monitoring well network and have a flat water table, you may need to know the position of the measuring point to within 0.01 foot horizontally and vertically (vertically is much more difficult to get good data). If so, you need to use surveyor grade GPS systems and a licensed surveyor. However, sometimes even that won’t work. (Buy me a beer sometime and I’ll tell you the story of the $60 million survey error by an RLS resulting in four years of litigation.)
If you are just trying to be able to relocate something in the field that is pretty unique like a cave entrance or spring, maybe 3 meters accuracy is good enough and a hand held GPS unit would be fine. So, depends upon what your trying to map or record. Bill, excellent article and thanks for sharing. Geary Schindel gschin...@edwardsaquifer.org<mailto:gschin...@edwardsaquifer.org> From: Texascavers <texascavers-boun...@texascavers.com> On Behalf Of Diana Tomchick Sent: Thursday, September 27, 2018 12:51 PM To: Cave Tex <texascavers@texascavers.com> Subject: Re: [Texascavers] Notes on GPS, GNSS, and GIS for Cavers I think the best take-home message in your PDF is the accuracy for a cell phone or tablet can vary depending upon not only the device but also upon the software used. A useful addition to the PDF would be a table that lists the estimated accuracy for different devices that people actually use in the field, including handheld consumer GPS units, cell phones, Bad Elf, etc. I know the information is in the PDF, but having a table that collects all the information together would be extremely useful, especially when one needs and easy and quick way to explain to someone why using their internal Compass app on an iPhone isn’t as accurate as a handheld consumer GPS unit. Diana ************************************************** Diana R. Tomchick Professor Departments of Biophysics and Biochemistry University of Texas Southwestern Medical Center 5323 Harry Hines Blvd. Rm. ND10.214A Dallas, TX 75390-8816 diana.tomch...@utsouthwestern.edu<mailto:diana.tomch...@utsouthwestern.edu> (214) 645-6383 (phone) (214) 645-6353 (fax) On Sep 27, 2018, at 11:23 AM, William R. Elliott <speodes...@gmail.com<mailto:speodes...@gmail.com>> wrote: Diana, I looked up what I could about iPhone XS Location. All Apple said was this: Assisted GPS, GLONASS, Galileo, and QZSS Digital compass [apparently the same old Compass app] Wi‑Fi Cellular iBeacon microlocation [used indoors at stores via Bluetooth) So, we don't know if the accuracy has been improved. With the same old Compass app, the precision is cut off at one second, about ±30 m. As I mentioned in my article, get the free Compass 55 app and you'll achieve a precision of ±0.00001 degree, or about ±1m, but that's not the same as the phone's accuracy, which may only be ±10 m. I've found that if you ask a salesman about these things they'll give you anecdotal information or a guess. They often brag about how the phone uses cell towers to improve its accuracy, but that's not what we want out in the wild. Good luck! William R. (Bill) Elliott speodes...@gmail.com<mailto:speodes...@gmail.com> 573-291-5093 cell On Thu, Sep 27, 2018 at 10:45 AM Diana Tomchick <diana.tomch...@utsouthwestern.edu<mailto:diana.tomch...@utsouthwestern.edu>> wrote: I would be curious to know the accuracy of the latest iPhoneXS models. Diana ************************************************** Diana R. Tomchick Professor Departments of Biophysics and Biochemistry University of Texas Southwestern Medical Center 5323 Harry Hines Blvd. Rm. ND10.214A Dallas, TX 75390-8816 diana.tomch...@utsouthwestern.edu<mailto:diana.tomch...@utsouthwestern.edu> (214) 645-6383 (phone) (214) 645-6353 (fax) On Sep 26, 2018, at 11:01 PM, William R. Elliott <speodes...@gmail.com<mailto:speodes...@gmail.com>> wrote: Attached is a pdf article I wrote for the Texas Cavers list. Here are some notes on tablets, cell phones, GPS (Global Positioning System), and apps that cavers might use for cave projects, especially apps that are free or not too pricey. GPS and GIS (Geographic Information System) are my sub-hobby within caving. I recently experimented with the Bad Elf GPS Pro and a Windows tablet among other things. The procedures to make these things work together are not completely spelled out in the user manuals, so I had to figure things out by testing. New devices are coming on the market. Maybe this article will save readers some time, and I welcome discussion of these topics. Thanks, see y'all at TCR, William R. (Bill) Elliott speodes...@gmail.com<mailto:speodes...@gmail.com> 573-291-5093 cell <Notes on GPS GNSS GIS Elliott.pdf>_______________________________________________ Texascavers mailing list | http://texascavers.com<http://texascavers.com/> Texascavers@texascavers.com<mailto:Texascavers@texascavers.com> | Archives: http://www.mail-archive.com/texascavers@texascavers.com/ http://lists.texascavers.com/listinfo/texascavers ________________________________ UT Southwestern Medical Center The future of medicine, today. _______________________________________________ Texascavers mailing list | http://texascavers.com<http://texascavers.com/> Texascavers@texascavers.com<mailto:Texascavers@texascavers.com> | Archives: http://www.mail-archive.com/texascavers@texascavers.com/ http://lists.texascavers.com/listinfo/texascavers _______________________________________________ Texascavers mailing list | http://texascavers.com Texascavers@texascavers.com<mailto:Texascavers@texascavers.com> | Archives: http://www.mail-archive.com/texascavers@texascavers.com/ http://lists.texascavers.com/listinfo/texascavers
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