https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x I did this quite a few years ago but in the graph in supplimentary material it shows how the accuracy of one consumer grade gps varies over time (at a fixed point). At the time I also did a lot more measurements using mobile phones and consumer grade units on a grid of points in the field, that was not published but basically the phones were often as good as if not better than the consumer grade gps units especially when using certain apps to average points. [https://besjournals.onlinelibrary.wiley.com/cms/asset/1c8a8949-7fe4-48ea-beb9-01d4efee7ddf/mee3.2011.2.issue-6.cover.gif]<https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x> Where are my quadrats? Positional accuracy in fieldwork - Dodd - 2011 - Methods in Ecology and Evolution - Wiley Online Library<https://besjournals.onlinelibrary.wiley.com/doi/full/10.1111/j.2041-210X.2011.00118.x> Introduction. There has been much written about sampling design, spatial scale and the need for permanent plots in ecological long‐term monitoring, for example, the paper on spatial scaling in ecology has been cited over 1500 times, but one frequently ignored issue, intimately associated with sampling design, scale and permanence of plots, is how to locate positions accurately. besjournals.onlinelibrary.wiley.com
________________________________ From: Qgis-user <qgis-user-boun...@lists.osgeo.org> on behalf of Nicolas Cadieux <nicolas.cadi...@archeotec.ca> Sent: 23 May 2020 16:34 To: Randal Hale <rjh...@northrivergeographic.com> Cc: qgis-user@lists.osgeo.org <qgis-user@lists.osgeo.org> Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone CAUTION: This mail comes from outside the University. Please consider this before opening attachments, clicking links, or acting on the content. Hi, This is a very interesting list. It basically confirms what I thought. Consumer Point and shoot deceives are all around 2-6m with no canopy. The average multiple positions basically give you a better idea as a gps may get lucky. It would be nice to have the full methodology for this and more data (like the number of satellite and the position of the constellation and the gps price list) but it’s very interesting none the less. I was also happy that the data confirms the precision of the gps Sx-Blue 11. This claims to be sub meter and my tests indicated that on our office unit but it’s nice to see it done elsewhere. For about 2000$, this gps is pretty good. As for the rest, the difference between 150$ and 1000$ is probably more a function of the options (like maps and screen size...) and not a question of precision. It would be nice to know what gps chips they are running... Interesting thing also is that based on my reviewing the data on my phone (without graph or cross tabulation tables) is that the Glonas Constellation does not seem to help much. Quick stats on this list would confirm this. Maybe this is just a figment of my imagination because there’s only so much information you can grad without running proper stats. Thanks for the post. Nicolas Cadieux Ça va bien aller! > Le 23 mai 2020 à 09:02, Randal Hale <rjh...@northrivergeographic.com> a écrit > : > > One other thing that may or may not be of use but the USDA Forest Service > Publishes a GPS Receiver Report that covers phones - and that's helped if > I've had a client go "Well I have a Apple <something> or a Android <thing>". > At least I feel slightly better going "good enough" or "no not good enough". > > It should be good worldwide (but I will admit I think phones are my 'tech > ceiling' these days) but your mileage may vary. > > https://www.fs.fed.us/database/gps/mtdcrept/accuracy/index.htm > > Randy > >> On 5/22/20 8:55 PM, Priv.-Doz. Dr. Maria Shinoto wrote: >> Somehow I did not follow the discussion, but like to add some of our >> experience. >> >> We are doing field work in a remote region in the southern Japanese >> mountains, archaeological surveys on the ground based on LiDAR data. >> >> A simple Garmin etrex10 is mostly reliable in an area of 40cm by 40cm around >> a measured point, if used repeatedly at this point and the point is located >> in the middle of a valley. Even cell phones do a good enough job. As soon as >> we get closer to the steep slopes, the accuracy of the Garmin is less than 5 >> to 10 meters. We can check this with the detailed LiDAR based map, and >> geologists told us, that even an expensive device could not be more precise >> under these conditions. So we decided to measure traditionally on the ground >> if precise measure is necessary, otherwise note the GPS data and the >> location as shown in the map. >> >> To sum up, we came to the conclusion not to spend money on an expensive GPS >> that may not work in the shadow of steep slopes -- or in the streets of New >> York. -- I appreciate any additional advice, and hope that this experience >> can save Steve's organisation some money... >> >> Best, >> Maria >> >> >> >>>> Am 23.05.2020 um 03:54 schrieb Stephen Sacks <sack...@earthlink.net>: >>> >>> In order to make widely available some wise advice, I'm sending to this >>> list a message I received from Neil B. In addition to Neil's message >>> below, I want to mention that Nicolas Cadieux also provided similar >>> information, saying I'd have to pay around $1,000 for equipment that gives >>> consistently accurate location coordinates. And thanks, also to Falk >>> Huettmann and Bernd Vogelgesang for their replies. >>> >>> >>> Message from Neil B: >>> >>> Hello Stephen. >>> Glad that you're having su _______________________________________________ Qgis-user mailing list Qgis-user@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
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