ZED-F9P/GPS-RTK: RTCM UPDATE IN ROVER NOT PROVIDING EXPECTED ACCURACY

GPS/GNSS Development Boards
1

I’m having issues getting the RTK-GPS system with the ZED-F9P to receive the advertised accuracy:

  • 2.5m without RTK

  • 0.010m with RTK

    • I have setup the two ZED-F9P units in u-center, following the setup from "ZED-F9P Integration Manual (pg. 96-104),” which can be found here: https://www.u-blox.com/sites/default/fi … 802%29.pdf. I have set the system up using I2C as the transmission means, not UART1. ZED-F9P is connected to the RedBoard via Qwiik connect, with a XBee Expansion board and XBee Pro Module used as communication between the Rover and Base (see Figure 1).

    Figure 1. Rover Setup with I2C.png
    Figure 1. Rover Setup with I2C.png1996×1419 356 KB

    Figure 1. Rover Setup with I2C

    The base station, that is on a tripod with a base plate, is using the code based on the following example:

  • Example2_StartRTCMBase

    • I am able to see the bytes being transmitted from the base station. I am passing the correction data across XBee through I2C and using the “pushRawData” method to update position. I was expecting to be able to get the resolution advertised with a base station and rover, yet I am not getting what I was expecting.

    I have tried multiple builds on the Rover from the examples provided (https://github.com/sparkfun/SparkFun_u- … es/ZED-F9P). I need accurate latitude, longitude and altitude, yet none of these seem to work as expected:

  • Example5_RelativePositioningInformation

  • Example3_GetPosition (updated with pushRawData)

  • Example2_NMEAParsing (updated with pushRawData)

    • The system receives Latitude, Longitude and Altitude position. However, I am getting > 5 m deviation. The data taken below is from a stationary rover sitting next to the base station. The data is varying randomly within a 6.56 m circle (see Figure 2 below).

    Figure 2. Position Deviation shown by Min & Max points.jpg
    Figure 2. Position Deviation shown by Min & Max points.jpg1433×695 122 KB

    Figure 2. Position Deviation showed by Max & Min points

    Can you please give me advice on what I may be missing?

    Hardware:

  • Sparkfun RedBoard (DEV-15123)

  • Sparkfun XBee Shield (WRL-12847)

  • XBee 3 Pro Modue - RP-SMA Antenna (WRL-15131)

  • 2.4GHz Duck Antenna RP-SMA - Large (WRL-00558)

  • GPS-RTK ZED-F9P Breakout (GPS-16481)

  • GPS/GNSS Embedded Antenna - 1m (SMA)(GPS-14987)

    • Thanks,

    Katherine :blush:

    2

    Try moving away from buildings and trees and see if that helps.

    3

    Thank you for your response. Sadly, I get the same result if I am placed in the middle of the yard.

    NOTE: I find the same variations happening whether I’m using u-center or running the program.

    Any advice would be appreciated!