8 Replies Latest reply on Oct 17, 2016 5:59 PM by CarlSchwarz

    Accuracy gps

    barand

      Dear filemaker users,

       

      I would like to determine the GPS location with an accuracy of 1 cm on an ipad. Is it possible to write that accuracy in the "Location" code or can't it be configured lower than 1 meter?

       

      I will use an external GPS that should make this possible, which will be bought based on if filemaker allows an accuracy of preferably 1 cm.

       

      Yours sincerely,

       

      Baran Demir

        • 1. Re: Accuracy gps
          jbante

          I don't know how your particular GPS receiver will interact with the iPad, so I can't say if the Location and LocationValues functions built-in to FileMaker Go will request a reading from the external receiver or stick to the location sensors in the iPad. Some external receivers do claim to "take over" responsibility for location sensing from iOS, so it's plausible. If the combination of iOS, FileMaker Go, and your GPS receiver allow it, that call would look like "Location ( .01 )". Do you have a link to the product page or technical manual for your receiver?

          1 of 1 people found this helpful
          • 2. Re: Accuracy gps
            barand

            Thank you for your reply.

             

            Their distributor claims that the external GPS can "take over" the responsibility for location sensing from iOS.

            • 3. Re: Accuracy gps
              philmodjunk
              with an accuracy of 1 cm on an ipad

              Can GPS technology really produce that level of accuracy? I've only read of accuracy from GPS technology in general in terms of meters or feet so this seems a truly extreme level of accuracy...

              • 4. Re: Accuracy gps
                barand

                http://www.sxbluegps.com/wp-content/uploads/2016/08/2016-08-15-iSXBlue-III-GNSS-EN_web.pdf

                 

                This is the device for which I stated my question. I am hoping on getting my hands on a trial receiver..

                 

                I am not a GPS expert so I cannot explain why this level of accuracy seems possible, sorry.

                • 5. Re: Accuracy gps
                  jbante

                  Can GPS technology really produce that level of accuracy? I've only read of accuracy from GPS technology in general in terms of meters or feet so this seems a truly extreme level of accuracy...

                  Limiting yourself to GPS proper — the satellite-only positioning system maintained by the US military — 1 cm accuracy is not possible. iOS devices have never limited themselves to GPS; but adding WiFi and cellular antennae trilateration and GLONASS doesn't quite get you down to 1 cm either. Additional techniques can achieve this kind of accuracy.

                  • 6. Re: Accuracy gps
                    CarlSchwarz

                    This GPS uses RTK, or an reference station to improve the accuracy.  This can get up to centimeter level accuracy, depending on how accurate the GPS location has been recorded for the reference station.

                    The iPad should receive the accuracy information from the external GPS and report that.  I haven't used an external GPS with an iOS device for many years, but I do recall it working that way.  Certainly every other mobile phone that I have used with an external GPS receiver has worked that way and iOS should be no different.

                    • 7. Re: Accuracy gps
                      Vaughan

                      From Stackoverflow:

                      What is the maximum Theoretical accuracy of GPS? - Geographic Information Systems Stack Exchange

                       

                      The United States government currently claims 4 meter RMS (7.8 meter 95% Confidence Interval) horizontal accuracy for civilian (SPS) GPS. Vertical accuracy is worse. Mind you, that's the minimum. Some devices/locations reliably (95% of the time or better) can get 3 meter accuracy. For a technical document on that specification you can go here.

                      • 8. Re: Accuracy gps
                        CarlSchwarz

                        Just pointing out that he is using a differential GPS system, the same as surveyors use to get sub-inch accuracy.  A brief explanation here How does DGPS Work? - YouTube

                        It will require a fixed base station that has a known GPS location, usually done by averaging a the GPS coordinates of a fixed position over a long period of time, e.g. 24 hours.