Flight in 3D dgps. Is there a problem?

ArduCopter
1

Hi.
I am curious about the status of GPS this time, so I am asking a question.

The number of satellites is 18-19, which is enough.

HDOP is also very good at 0.5 to 0.7.

However, in the lower right of the Hud window, 3D dgps is displayed instead of GPS: 3D Fix.

In fact, the Compass value in EKF is very unstable during flight.

The EKF character in the Hud window has turned white-orange-red.

Can this cause major problems in flight?

For example, a fall or going somewhere else.

Actually, I confirmed that the error from the home point at the last RTL of the mission flight is larger than expected.

What exactly is the difference between 3D fix and 3D dgps?

Do you have any Ardupilot documentation that you might want to refer to?

2

DGPS isn’t a problem. It’s good.

https://ardupilot.org/copter/docs/common-gps-how-it-works.html#dgps-corrections

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3

If so, why is EKF’s compass item constantly high?

Which is better, 3D Fix or 3D dgps?

4

Try moving your GPS antenna further away from other electronics.

5

I have Here1 and Here2.
Moving the GPS Antenna means moving Here?

6

yes. Move both Here units higher up.

7

I tried. It’s still 3d dgps. I have another same quad. This 3d fix works well

8

DGPS is an enhancement. What is your GPS_GNSS_MODE and GPS_SBAS_MODE set to?

Ardupilot Wiki:
https://ardupilot.org/copter/docs/common-gps-how-it-works.html

9

This is the default parameter for 4.0.5 Quad.

10

Well default is “leave as currently configured” and “no change” respectively so perhaps you should set it how you want it.

11

Try to change the GPS_GNSS_MODE to 65 which means GPS+GLONASS.
DGPS means Differential GPS and uses satellite based augmentation (SBAS).
GPS and GLONASS should give you 12-18 satellites depending on your location.

12

Thank you for answer.

As the person commented on the setting below, can I set Gnss_mode to 65?

13

This is currently no problem with flying with GPS_GNSS_MODE of 0 and 3D dgps (probably).

If I set this parameter to 65, does 3D dgps show better locking?

Or, if it is not 3D dgps, is there no problem with flying?

14

Disable Sbas modes. That’s it. It’s a Bitmask, check the constellations you have access to, with respect to h0ow many your GPS module can support simultaneously, and don’t check Sbas.

GPS
GPS1444Ă—535 74.1 KB

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15

a1
a11535Ă—215 45.5 KB

Is it correct to modify this parameter?

If I fix this, is there any way to see how it changed?

16

I am using here and here2 gps.

Looking at the product specifications here, it comes out like this,

Check all the things written here, and only uncheck sbas among them?

fff
fff908Ă—205 23.7 KB

17

As far as I know those can have up to 3 concurrent constellations. I would pick the 2 most useful for the region you fly in. I don’t know what those are for you figure it out. In the US I use GPS+GLONASS. I also use SBAS but if that’s not working for you don’t enable it.

18

Thanks for the reply.

Is there any way to check for a valid satellite?

I’ve been using Mp for quite some time, but I’ve never seen anything like that.

Of course I know Glonass, beidou and Galileo.
But I’m not sure how to check which ones are the most valid for my current location.

19

MP won’t tell you this. A Google search will find plenty of resources.