Comments: SparkFun RTK Surveyor Hookup Guide

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  • Pardon me if this isn't the place, but I have a question about the "accuracy" values that get reported. I just got a Surveyor and connected it to a UFO antenna on my roof--not quite 2pi steradians of open sky but enough to get high 20's to low 30's in number of satellites. I'm looking at uncorrected rover data using the SW Maps app on an Android phone. I have recorded six series of 1000 to 5000 position measurements using the "Record Tracks" function (0 motion threshold, 2 seconds between measurements) for the fixed antenna and looked at the average position, as well as the standard deviation, max & min along each axis. It seems to me this should show be the baseline noise in the measurement. The GNSS status reported through SW Maps says that the X and Y errors are below a foot, and the accuracy is in the foot range, but the standard deviation of the long/lat measurements ranges from 2.5 to 9.5 X 10-6 degrees, and the lateral RMS of the lat and long standard deviations has been closer to 2 feet than 1--a best of 16" and a worst of 4 feet. So what does it mean when the accuracy for the measurement is said to be 1 foot, but the track shows a total range of X and Y of as much as 10 feet. Can't be accurate to a foot while wandering around by that much. What am I missing?

    • I'm assuming you are using an L1/L2 antenna, possibly the one we recommend. If you're using a different antenna, please let me know.

      The ~1ft horizontal positional accuracy reported by the Surveyor (SW Maps + ZED-F9P) are done without RTK and will vary over time based on environmental conditions. This positional accuracy is best seen in moving measurements (distance). Holding an antenna still and expecting the same repeatable position over hours or days will be very difficult. That's where PPP (precise point positioning) is going to be much better.

      • Thank you Nate! I was going to reply sooner, but figured I should do more homework first. Yes, I've got the UFO antenna that SF sells. I've been following the breadcrumbs you've done a good job of leaving, and am learning more about PPP and u-center. Talk about a novice! The measurement of averages, standard deviations, max, and min I mentioned above was all done through SW Maps and Excel. Today I discover that all the same information is there in the u-center Statistics window--in real time. Duuuh! Still a bit skeptical about whether the reported accuracy would qualify as ISO accuracy, but will move on to acquire data for PPP.

  • Admitted ultra noob (I coined it), ordered units for base/rover setup, shipping (paid one step up) awesome fast, equip looks cool. But...can't use it yet, (ordered all suggested and antenna adaptor connectors as suggested from amazon) not mentioned... and not included is cable to connect "UFO" antennas to surveyors. I would gladly have purchased if listed as needed. To make matters worse, I live in no mans land, (not even a radio shack), what cables should I get (from SparkFun, or other source)I will be using a close coupled setup per SparkFun example.

    Also correction data service here in PA is all subscription, about $350/yr.

    • Nate / last year * / 1

      Sorry for the confusion! I don't quite follow your question. I believe you are asking about the cable that goes from the RTK Surveyor to the L1/L2 antenna. [edit] We finally got cables in! Male TNC to Male SMA is what you need.

      Please feel free to share links to data services. They are often hard to find.

      • PA and surrounding correction data service: https://www.keynetgps.com/

        Note error in my first post, it is not 350/yr it is 375/month, 3k+/yr

        • Where are you located in PA? I'm in central...I agree, the subscription service is expensive for the hobbyist. I'd love to be able to eventually find enough people around my area that would want to set up reference stations like in this tutorial:

          https://learn.sparkfun.com/tutorials/how-to-build-a-diy-gnss-reference-station?_ga=2.72725843.1974062458.1608236161-1631564577.1605642860

      • Just a heads up...I'm using that same cable from Amazon, and it has worked fine for now, but I was disappointed that the TNC connector body is raw aluminum as opposed to chromed brass. Aluminum being so soft, I can't imagine the threads on the TNC are going to last that many screw-unscrew cycles compared to chromed brass or hard anodized aluminum. I look forward to getting SF's cable when it comes out.

      • Thanx...ordered, I will try to re find that pay service link and post it....

  • Curious (and lazy as I could go dig through the firmware code myself)...what are the default survey settings for survey time and survey accuracy when the device is in base station mode?

    Secondly, this device is awesome! I just last month built a ZED-F9P base/rover pair with Telemetry Serial Radios using the SF tutorial. Mine has integrated arduino and OLED display. I can tell this RTK Surveyor product is more streamlined and targeted for immediate use and less targeted for hacking, but I would really appreciate a brief section in the guide how to compile and upload revised/customised firmware, for those of us without an established ESP32 toolchain.

    • Nate / last year * / 1

      2nd Question: It's just Arduino! Follow this guide to get the ESP32 Arduino core installed. Then select 'ESP32 Dev Module' from the ESP32 boards list (first one) (this is all in the notes at the top of the firmware). You'll find links to all the necessary libraries within the firmware (just click and Arduino should present you with the lib you need to install). The firmware is big, but I hoped it's written well enough that you can follow. Once you have the 5 or so libs installed, attach a USB C cable to the ESP32 port. Updating the firmware is as easy as hitting the upload button in Arduino.

      I've added System Configuration and Firmware Updates sections to the tutorial.

      Shhh. Don't tell anyone but I've got auto-detection of our Qwiic OLED built into the core firmware (v1.0). It's doesn't work currently and it's a silly idea to have an OLED hanging off a unit in the field via a Qwiic cable but it's an obvious add on. Our OLED library is falling over peculiarly when I compile against the full firmware (but works when used in a stand alone display sketch).

    • Nate / last year / 1

      Keep the good questions coming! Survey-in is set to 5m required position accuracy and 60s min observation time as recommended by u-blox. It's set here in the firmware. I plan to expose this in a future firmware release so that the user can set their own values but without going into extreme depth, you don't benefit much from extreme (hour+) survey in times. It's better to gather RAWX (oh shoot, I forgot to add that to the tutorial) and do PPP.

  • Regarding the Telemetry Serial Radios, can pairs of these radios be mixed and matched between the pairs that ship in each box, without any reconfiguration? In other words, if I buy two pairs of these radios (four in total, let's call them Pair1RadioA Pair1RadioB Pair2RadioA Pair2RadioB), can Pair1RadioA communicate with Pair2RadioA without reconfiguration? I am not asking about one-to-many, only about mixing one-to-one pairs. Thanks!

    PS: I haven't found any great manufacturer documentation of the radios. Nate, do you have a link to documentation of how you set the radios to "different net IDs."

    • Nate / last year / 1

      Good question and thanks for the clarification. The short answer is yes. All these radios ship with same settings so if you turn on any two, they'll connect by default. If you turn on three (because I wanted to see what would happen) they will attempt to do one to many but it gets really dicey because both 'remote' units will attempt to ack back to the transmitter and packets start to collide.

      Please see the documents tab on the 500mW radio product page. The AT command set is listed as well as a few tutorials.

  • This link in the guide is 404 as of 20201204: https://www.sparkfun.com/products/17496

    • Nate / last year / 1

      Thanks. Fixed. We have a cable coming in but it didn't arrive in time for launch. We'll get it listed as soon as possible.

  • Why not add the radio inside the enclosure? The all point of RTK is two units "talking" to each other. Attaching the radio externally like this is cumbersome and prone to problems in the field.

    • Nate / last year * / 1

      What xsk8rat said. By putting the radio inside the unit you begin to lock yourself into a certain technology whereas we wanted a BYOR (bring your own radio) approach. If you need 1 mile, 915MHz radios work great. If you need 5 mile, LoRa might be an option (haven't tested). If you have cellular coverage, you don't need a radio at all, you simply use your phone to push RTCM to the unit over Bluetooth SPP. And on a side note, I find the Velcro convenient so that I can swap radios depending which station I'm closest to (I have 'SFE' and 'DwnTwn' set to different net IDs).

      The JST connectors are locking and I haven't had an issue with the few months I've been throwing my unit around. I readily admit this is not a $10,000 Trimble. But it's far better than the handful of boards tapped together I used to use!

    • xsk8rat / last year / 1

      Maybe different markets have different frequency requirements like LoRa and cellular. Other folks may want to use different types of communications. Those are things i don't know a lot about. This makes the solution a little more flexible. But you may be right, the wires and all can be an issue if one is not careful.


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