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My question might be a bit off-topic but I don't know where else to ask.

When I do have a GNSS Module with integrated IMU and Dead Reckoning, for example, the Ublox ZED - F9K.

Does it still make sense to use a Filter for fusing GNSS and IMU / Odometry data or is that not necessary as the Module is handling that for me?

Or will the Dead Reckoning just enhance the precision after applying a Filter even more?

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  • $\begingroup$ Ah, let me google and see if I can answer you question. I first skimmed the following ZED-F9K Product Summary: u-blox.com/sites/default/files/… $\endgroup$
    – tlfong01
    Commented Sep 22, 2020 at 2:09
  • $\begingroup$ I also read the module product sheet from Sparkun and made a features summary: "GPS-RTK2 Board (ZED-F9P) Product Sheet - SparkFun": mouser.hk/new/sparkfun/sparkfun-gps-rtk2-board (1) TTFF = 25s (cold), 2s (hot); (2) Horizontal accuracy = 2.5m (without RTK), 10cm (with RTK); (3) Nag rate = 25Hz max $\endgroup$
    – tlfong01
    Commented Sep 22, 2020 at 2:27
  • $\begingroup$ I then browse the SparkFun GNSS 23 Products Catalog: sparkfun.com/categories/tags/gnss, and the GPS-RTK ZED-F9R Dead Reckoning Breakout - SparkFun US$300 sparkfun.com/products/16344. $\endgroup$
    – tlfong01
    Commented Sep 22, 2020 at 2:37
  • $\begingroup$ I also skimmed SparkFun's "GPS-RTK Dead Reckoning ZED-F9R Hookup Guide": learn.sparkfun.com/tutorials/…. $\endgroup$
    – tlfong01
    Commented Sep 22, 2020 at 2:43
  • $\begingroup$ I then read SparkFun's Hookup Guide: "GPS-RTK Dead Reckoning ZED-F9R Hookup Guide (Python and Arduino)": learn.sparkfun.com/tutorials/…. $\endgroup$
    – tlfong01
    Commented Sep 22, 2020 at 2:47

1 Answer 1

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Question

Is it necessary to use any filter to fuse Ublox ZED-F9K's GNSS and IMU/Odometry data?

zed-9fr

Answer

My answer is NO, for the following reasons:

(1) GNSS and IMU are independently developed modules with matured software. It is unlikely for the vendor to "fuse" them at the hardware level. A more efficient method is to let the MCU/SBC to talk to either or both guys using I2C, UART, or SPI.

(2) uBlox uCenter uses very simple, text based NMEA0183 protocol, and update rate is of the order of 25Hz, so the user can easily pass the slow GNSS data to IMU for processing.

Discussion, Conclusion, and Recommendation

I think it is not a good idea to use the expensive US$300 ZED-F9K module to do any feasibility studies. I would suggest to use two separate modules (1) UART NEO-8M, (2) Any I2C IMU and use Rpi python to do any system integration test.

References

(1) SparkFun GNSS Products Catalog

(2) GPS-RTK ZED-F9R Dead Reckoning Breakout - SparkFun US$300

(3) SparkFun GPS-RTK Dead Reckoning ZED-F9R Hookup Guide (Python)

(4) GPS Fixing Time Problem Q&A - tlfong01, EE SE, 2020sep03

(5) Neo-6M/7M/8M GPS Module Setup/Fix/Update Problem Q&A - tlfong01 Rpi SE 2020jun18

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