Did you ever find the answer to this question?
Keep a distance between them
As Amilcarlucas is implying (I think) the issue is apparently that the yellow GPSB line is directly under one of the other lines so it canāt be seen. A manual way to confirm this would be to convert the .bin file to a .log file (MPās dataflash tab has an option to do this), the open the log in a text editor and delete the GPS, GPS2 and POS messages so that only the GPSB message remains.
Another option to is to raise an enhancement request for the MP to give the user the option to display only some of the 4 positions.
The problem is not on the map. Actually there is no GPSB message in the log; only GPS, GPA, GPS2, GPA2 and POS.
I fixed that bug in a GPSB bugfix PR. But I am not sure if it has been merged already.
I have it locally fixed on the 4.0 branch and on master. So backporting is possible. 
Do you need more help, or can you take it from here?
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What is the minimum recommended distance between the two GPS units? Is this mentioned in any documentation? Thanks
No, no documentation, and there is no magic number either.
For GPS Blending the docs are here but there is no requirement that the GPSs be spaced apart.
GPS-for-Yaw requires the two GPSs be spaced at least 30cm apart to allow getting a good heading. This feature is only available on ArduPilot-4.1 though which hasnāt started beta testing yet.
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Thanks! The plan is to use two Here3 units in CAN1 and CAN2, one as primary and one as backup.
Ok, that should work but there is one issue to be aware of. Copter-4.0.x may somewhat randomly change the order of the GPSs meaning GPS1 and GPS2 can be swapped around on each boot meaning that you wonāt be able to set the GPSx_POS_X/Y/Z parameters because they could end up being applied to the wrong GPS. Note that this doesnāt affect the compasses, just the GPSs.
Its a VTOL, does that also apply to Plane 4.0.7? Would blended be better to use with two CANs? Iād really only like to use two CANs because of the distance they will be from the Cube. I was told its better to use CAN for long GPS cables. Thanks
Sir IN GPS1
2=GPS_TX
3=GPS_RX
reverse these connections. pin diagram is wrong at this point only. sorry for late reply, I did not see. please forward this to relative person who are handle this pin diagram.
Will this be resolved in Copter-4.1? I have to Here3 GPS units and was wondering about GPS1 and GPS2. I have the GPS_POS_X/Y/Z set for these but have been having some strange behavior and was curious if the cause was this. I want to keep the dual GPS setup but should I set the position X/Y/Z values back to 0? This quad is large at about 1.5 meters from motor to motor. Thanks for you help.
It is fixed in 4.1. CAN GPSs are fine now.
Hi.
I want to askā¦
I installed two uavcan gps, the copter behaves a little strange. The flight log looks like zigzags.
With the option of installing two gps: one usart gps and one uavcan gps - the flight schedule is normal. When installing two uavcan there is
feeling that the averaging algorithm between them is not working properly. Data from two gps are alternately connected to each other in a broken line, a zigzag.
This is a super cool feature.
When blending, what happens if one gps fails? I assume that some sort of failsafe been taken into account for this?
Is this referring to the actual factory that made the ships? For example, if I have two M8Nās, but from different factories, is this fine? Or something in the actual chip making process that differs and causes inconsistencies?
If one GPS fails the blending will switch to use 100% from the working GPS.
Two M8Ns (even if they are from different GPS manufacturers) should be fine. The issue is that different types of GPSs are inconsistent in their reported accuracies and this affect the balance of the blend. If the same model of Ublox is used then it should be fine.
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Thanks. I was considering for a moment blending my old 3DR Neo-7 with a newer M8N, but will not.
My guess it that might actually be fine. For a long time I blended a UBlox6 with a UBlox7 and didnāt notice any bad behaviour actually. So we donāt recommended it but personally I havenāt noticed any issues.
I will likely give it a try at some point with the UBlox Neo-7 & UBlox M8N. If so, I will report how the combo works. Itās hard to spend the all of about twenty five bucks for another M8N whilst losing the sentimental retro factor of the 3DR, which seems to still be a great gps.
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