uBlox ZED-F9P series of GPS is their new and first multiband GPS series. Until now we have all used mostly their M8 series which was already very good GPS modules. I have watched Tridge’s blog on his own very technically detailed testing which triggered me to do this comparison between F9 and M8 series of uBlox GPSs.
I have so far used M8 series GPSs on all of my UAV builds so far with great satisfaction.
The fact F9 series are multiband GPSs, there should be a good improvement on performance (precision, speed of acquisition)
To test it out, I connected an Ardusimple F9 GPS eval board to a Pixhawk1 board on GPS port 1. I simultaneously connected a M8 GPS on GPS port 2.
Both antenna were placed in the exact same location and orientation, inside a a three stories home. The idea is to see in a difficult non clear sky view how these two uBlox modules compare.
The results are quite self explanatory… as shown in the video.
Well, not sure what this test really means.
First, you need to test in an outdoor environment, with an unobstructed view of the sky.
With sat acquisition times of >1.5 hours indicates that this test was done indoors, meaning that the results are interfered by multipath and other effects and not meaningful.
Second, acquisition time depends on if the position has been cached before or not.
I am using the exact same m8n as in your test, typical time to get a fix with 18+ GPS and Glonass sats is <1 minute.
And lastly, the quality of a GPS fix is not necessarily dependent on the number of acquired sats, and while HDOP is a good indicator, there are more parameters to look at.
Don’t get me wrong, the F9 is revolutionary in terms of accuracy and price/performance compared to a M8P RTK GPS. But the main difference lies in its multiband RTK capability and position update frequency.
To compare it with an M8N is like comparing a brand new Tesla Model S with a 10 year old Toyota Corolla.
That was the whole point of my “non scientific” test to compare in the exact same conditions a F9 vs a M8 GPS: put the antenna in an obstructed indoor difficult setting with multipathing in order to be able to compare F9 and M8. This is of course not at all a scientific meaningful test.
It’s nice to know, I guess, what the GPS can do inside a 3-story house, as that does say something about relative performance…but for me, I just want to know…in my typical flying situation…OUTSIDE and in the CLEAR, is there really any practical difference between the 8 and 9?
You got it. The relative performance of the chips remains independently of the environment. So even in a clear sky you’ll get a better relative performance. Check Tridge’s more scientific measurements in prevoous blogs that confirms this.