• The system claims that by storing measurements at time of camera trigger signal and post process to get the exact position, there is no need of radio link for sending base station data to the rover on the mapping UAV; it avoids potential RTK unavailability issue if there is radio link corruption.Such system is for applications not using RTK to steer UAV, but only to take measurements for post-processing. We can also provide similar post-process software for NS-HP-5S users if there is a need for it.

        • Mr Huang, I'm following your products since yours indegogo campaign and the very beginnings test on the highway.

          We are interested for a GPS receiver (no antenna) capable to store L1/L2 (even L1 only is a good start) code and carrier-phase data in raw format, a simple software to convert raw data into RINEX format and a simple device that record GPS time-tag of the moment when the picture was taken (from the blitz hot-shoe or other similar devices).

          Is any of your products ready for those two task, if yes then send me a RINEX file to look into.


          • For aerial mapping, using time tag to derive position may be questionable. If UAV is flying at 50Km/hr, even at 10Hz raw measurement update rate, it’s 139cm between two 10Hz locations. Unless UAV is flying straight at constant velocity, otherwise it’s not likely to get correct position within couple centimeter interpolating using time tag. Those more expensive RTK receivers and our NS-HP-5S can calculate RTK position at occurrence of the trigger and also output additional raw measurement for the trigger instant for later post processing, thus able to get couple centimeter accuracy regardless how UAV is affected by wind or even when flight path is non-linear. For example, maximum position tag error of NS-HP-5S is bounded by distance UAV moved in 1 millisecond on top of 1cm + 1ppm RTK error; i.e. for 50Km/hr and 5Km baseline that’ll be 50e3x100cm/3600/1000 + 1cm + 0.1cm x 5 ~= 3cm. Reason for 1 millisecond UAV moved distance error is due to fundamental 1 millisecond GPS internal processing rate, rounding to nearest millisecond GPS measurement.   


            This ublox NEO-M8T is capable of L1 GPS/GLONASS raw measurement and time tag function, RTKCONV of RTKLIB can convert to RINEX.


            NS-HP-5S is L1 GPS + B1 Beidou type RTK, behaving mostly like L1 GPS/SBAS type for users in American continents. RTKCONV also works with raw measurement output of NS-HP-5S. Please send an email to to get example raw measurement binary file or converted RINEX file, and to avoid my hijacking this thread. 

            • Mr Huang,

              Thank you for your advice I've just sent you an e-mail

          • The time-tagger device we can built it ourselves, we need only the receiver and the conversion software raw-rinex

  • For GPS L2 of Precis-BX305, does it use L2C or L2P(Y) ?

    • its L2P(Y).

  • Dear everybody,

    Just out of curiosity, we have purchased both models so we could compare against our Novatel's OEM615 solution.

    Despite the fact that the people working on the company are not to be found in linkedin and/or the universities/projects they claim, and the fact that the sites they mention in Switzerland and California look rather strange in Google Street View, and the fact that was registered for just one year, we proceed with our tests.

    The BX303 model uses the uBlox's receiver and looks like it performs kind of a connection between the rover and the base station (so is reported on the User Interface). The precision is far from acceptable for our purposes, but it might be good enough for UAV's. At least it is still better than any single-GPS without correction.

    The BX305 uses Unicorecomm's OEM board (UB351), which should be equal or better than Novatel's. The User's Manual found in Tersus webpage explains a small protocol to configure and parse a small minimum amount of NMEA-formatted data. The manual found in Unicorecomm's webpage (in chinese) gives a bigger set of commands and logs. Among them, the 'authorization add' command, which brings us closer to what Novatel (and the rest of trusted providers) do for being able to activate the reception of data. For the moment, we have not been able to receive a GPS data/RTK-corrected position.

    Of course we have asked the provider what the workaround could be but at the moment, we are back to square one: GPS/GNSS L1/L2 receivers are expensive, high-end RTK algorithms and binary communication protocols top it up. Maybe uBlox's M8 plattform gives us some differential GPS correction, but they are still far from high-end.

    And this will be our last test for cheap L1/L2 GPS/GNSS RTK alternatives. We give of course, Tersus the possibility to redeem themselves but, looking at their English grammar, the low quality of the documentation and the lack of validation certificates, we do not hope the best.

    Hope this is useful, I apologise for the small rant.

    • hi gps_profi

      from the link, you can see lot's of our information over there. like many startup company, lot's of things need to be fixed (branding, marketing, docs, support), we are no except.

      In a nutshell, we are working seriously toward to an affordable L1/L2 board to the UAV market. As you know, it's huge work to do to finish the L1/L2 baseband and RTK engine, and also the User interface. hopefully the BX316 board is working in the lab, some trail customer are using the board. and also the BX315 and BX303 board are shipping to customer everyday....

      If you have any feedback when using the boards, just drop lines to describe the bugs, field report, or any non-workings to us.

      • Dear,

        A Linkedin page is not going to impress us. What we were looking for is accurate documentation, troubleshooting guidance and responsive e-mail support. Do your have any email contact except

        As I said, we are having trouble with the BX305. The receiver cannot even see any satellite despite being outdoors. when retrieving the BESTPOS log and "ERROR" field appears and the GPRMC log, second field shows a warning.


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