Correct settings for U-Blox related GPS modules

I like to make a sticky about u-blox related GPS modules settings that are necessary for a correct communication between ArduCopter.

This is because I buyed serval GPS modules from serval “drone shops” that where not setup correctly for use for our purposes.

As of certain release (don’t now when) I noticed the standard baud rate is now set at 115200.
Even if your module is set to 38400 it wil set it to 115200 on initialisation.

We use U-Center to setup our modules.

Basic settings:
depents on your module, If you have one that support multiple networks like GPS, Galileo, Glonass, BeiDou for the use in the European region we use GPS & Glonass.

on Navigation Modes we choose Pedestrian (for more precise hoovering)
or Airborne <1g <2g or <4g this is what most people use.

Protocol in: UBX+NMEA
Protocol out: UBX
Baudrate: 115200

By default it is at 1Hz refresh rate.
The higher this rate is the more data per second wil be send to our flight controller;
The maximum rate depents what type of module you use and what it’s capable of.

1000ms = 1Hz
500ms = 2Hz
200ms = 5Hz
100ms = 10Hz
55ms = 18Hz

Set Subsystem to Disabled
If set to enabled you need to wait at least five minutes till you get an 3D-fix.

These are the most importent settings for our drone.

However I noticed there is no HDOP information:

@G33RT have you found any problem with GPS_AUTO_CONFIG 1 and GPS_SAVE_CFG 2 ? On a u-blox GPS this should always arrive at the desired settings, and ensure that the settings are correct before takeoff. At a minimum I would let the autoconfig run and compare the settings generated from it.

At this point I strongly don’t recommend people configure the GPS from u-center as there seems to be a tendency to arrive at slightly broken settings. For example Pedestiran is not a navigation mode you ever want to fly in. (And without seeing your parameters for sure I can’t say, but I strongly suspect we are fixing this for you at flight time), Your rate setting is also absolutely incorrect.

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Yeah, im trying to figure out why uCenter should be used at all. Every. The drone sends the GPS receiver the configuration at boot, it’s part of the driver. Have you ever had problems with it?

Pedestiran is many time recommmended in forums because it gives a better position information.
I can confirm that, but mabe you are right and we all should use Airborne 4g make sence.

However if I connect the GPS to U-Center is still have it’s default settings Portable, 9600baud etc…
So pixhawk does not save the settings.

What about that RATE, please explain.
We all want to learn here.

Seems to me that none of the settings are saved as all default values are in u-center.

@G33RT can you paste all your GPS parameters? GPS_SAVE_CFG is not enabled by default, so we aren’t saving the settings unless you opt into it, but we will change what they are set to by default.

Pedestrian gives the lowest noise location information as long as you’re moving very slowly. That’s because it’s motion model assumes not much movement so it can low-pass the data like crazy. That’s absolutely HORRIBLE for a fast moving acrobatic vehicle. But… the data looks great while sitting on the bench so I can see how some think it’s better without doing any proper testing.

That raises a very good question about GPS configuration.

Our copters are large, not aerobatic, and move no more than 5 to 6 m/s, which is pretty pedestrian.

In this situation, as I am definitely not doing barrel rolls with it, would “Pedestrian” setting give a more stable GPS fix?

I don’t want to stir the pot, I am just wanting to explore the possibilities.

@mboland I can strongly assert the answer is no. I have a rather terrifying video recently of the affects of a AsteRx-M unit that was not fully configured and was set to pedestrian mode on a copter by accident. It introduced massive instability in the loiter mode and lead to the copter slaloming around the desired (stationary) position because of the filters. After fixing the filtering mode they did not have any other problems and the vehicle has been flying fine.

Thanks @WickedShell they are just the sort of anecdotes that help fill in the gaps of knowledge without going out and experiencing it ourselves.

I was just following the logic and had to ask the question.

Thanks for the time to answer.

After some more reading and mail from people who do use Pedestrian it is in some cases recommended because it’s simply better for photo or camera work in general.

@G33RT please provide a DF log file from one of those flights.

May I ask why you need a log file, can’t you just explain?
As of a complete new re-build I have no flights recorded yet.


There is a log of latest flight with Pedestrian mode selected.

There are two GPS,

GPS is the M8N of Navio card (firmware 2.01)
GPS2 is a M8N XL from Drotek (firmware 3.01)


There is not much movement, I just swapped all my ESCs to dys BLHeli and it is the first flight in the new configuration. Arducopter 3.5.3 OctoQuadX configuration.


@mlebret have you disconnected the Tx line from the flight controller to the GPS? A side note is I would recommend enabling a lot more of the arming checks rather then just the GPS Lock one.

@G33RT because log data actually backs up a point rather then turning it into an unfounded debate of I’ve seen/you’ve seen. I also strongly suspect that a large number of people who claim to have flown Pedestrian mode haven’t, as the GPS gets reconfigured by ArduPilot by default.

Drotek GPS wiring is Rx and Tx. No way to disconnect the integrated Navio2-M8N (SPI bus).

Arming Checks: I agree with you…