Just one issue I did not see addressed so far. The type of antenna a GPS uses makes a big difference. In forested landscapes, the eTrex, for example, with its flat antenna (like a single penny) is noticeable worse for receiving satellite data than a Garmin 60 series with an antenna formed like a stack of pennies. The more obstruction to the satellite's direct line of sight, the larger the difference. Jake
-----Original Message----- From: Qgis-user On Behalf Of Randal Hale Sent: Saturday, May 23, 2020 9:03 To: [email protected]; [email protected] Subject: Re: [Qgis-user] wishing for accurate lattitude/longitude from a cell phone 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 <[email protected]>: >> >> 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 success. I would like to start off by saying that it >> is best to always reply to the mailing list and not directly to the person >> who submitted the email. Mailing lists work really well in that there is a >> pool of people out there who may be able to offer advice or may have an >> alternate method to solve the problem that may turn out to be a better way. >> On the flip side by maintaining the email chain through the mailing list, >> the follow up emails that provide information are stored in the archives >> which benefits anyone searching the internet to have the complete trail of >> information. >> >> As far as your results they are acceptable for the device you're using. GPS >> in phones are never built to precision survey standards and there is no >> reason for them to be. If you're within 30ft of where the phone thinks you >> should be then you can easily navigate the rest of the way by visual sight. >> High end equipment to achieve sub-inch accuracy is probably in the range of >> thousands of dollars. One thing to keep in mind is there is a difference >> between the accuracy of a device and to what level of precision they >> display. While the app on the phone may display 8 decimal places of a >> lat/long coordinate and tell you if you have moved a foot, it doesn't help >> that the coordinate it is displaying is out +/- 30 feet. The accuracy of a >> device can also be affected by the environment where the device is being >> operated. In regards to cell phones, they use multiple sources to determine >> location such as GPS, cell phone towers, and wifi points to perform the >> triangulation. Lack of line of sight to satellites, signals from cell towers >> bouncing off of surrounding buildings, or someone's wireless router using >> inaccurate position information can all affect the accuracy of what is being >> displayed on your phone. >> >> So the question is how are you determining that the coordinates are wrong? >> If you have information that you trust to be authoritative then adjust your >> points to those values and carry on. I have no advice or opinions on >> inexpensive devices that may help with a more accurate reading. >> >> Please do not respond directly to me. This email account is not actively >> monitored and I don't always have the time to follow up with the emails. All >> the best with your endeavours. >> >> ~Neil B. >> >> On Fri, May 15, 2020 at 7:52 PM Stephen Sacks <[email protected]> wrote: >> Hi Neil, >> >> With your help, I have successfully brought the corners of our gardens >> back from Pennsylvania to the Promenade here in Brooklyn Heights, New York. >> Thank you. >> At the risk of wearing out my welcome, I'm now asking for more advice. >> My point features are approximately where they should be but not exactly, >> some points are just a few feet off and some are 10 or even 30 feet off. I >> imported the data trying both EPSG 4326 and 4269. >> I'm now convinced that the problem is due to (1) my Google Pixel 3 >> cellphone, (2) the app I'm using ("Latitude Longitude" published by >> gps-coordinates), and especially (3) my less-than-steady hands. I capture >> coordinates by standing at spot, waiting for the blue dot to settle, and >> then touching the blue dot. Often I don't touch the screen at exactly the >> right place. I tried another app ("GPS Coordinates" published by Financept) >> which is better in that it allows me to zoom in, but I'm still not always >> getting it right. >> I'm thinking now that I need specialized equipment. That is what I want >> to ask you. Can you recommend some inexpensive device that will allow me to >> simply press a button to record accurately the coordinates of the point >> where I'm standing? Keep in mind that this is a community project with no >> funding. I live on Social Security and a university pension, but I'm >> willing to pay something in the range of $50 or a bit more. Do you know of >> anything at such a modest price, or would I have to pay much more? Or >> perhaps you know of better software for my Android Pixel 3 phone. >> Thanks in advance for any advice you might offer. >> Steve >> >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> List info: https://lists.osgeo.org/mailman/listinfo/qgis-user >> Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user > _______________________________________________ > Qgis-user mailing list > [email protected] > List info: https://lists.osgeo.org/mailman/listinfo/qgis-user > Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user -- Randal Hale [email protected] (p) 423.653.3611 http://www.northrivergeographic.com _______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user _______________________________________________ Qgis-user mailing list [email protected] List info: https://lists.osgeo.org/mailman/listinfo/qgis-user Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-user
