No.fix

Reach Module / M+ / M2 RTK / PPK configuration
1

Hi everyone,
this time I experimented with Reach 10 green bars, waited a lot, but still couldn’t get fix solution.
Why does this occur?
Thank you in advance for any support.
Ernesto

no.fix.jpg1917×497 89.8 KB

1 Like
2

Hello!

What kind of base station are you using?

3

Hi Egor,
I use free Ntrip service of my region.
Here you have my settings:

  • gps, glo
  • GPS_GLONASS_5Hz
  • ntripcli
    -194.105.50.232
  • 2101
  • e.miorando
  • (my password)
  • single
4

I have two Reach modules wired together using the serial connection. They have been connected overnight once and today for 7 hours. They have been on float every time I’ve looked at them this afternoon. I will check them again in the morning.

I was able to get a fix this morning but only about 40% of the time.

My settings are also;

  • GPS, GLO
  • GPS_GLONASS_5Hz

I’ve used RTK GPS for over ten years for my farm tractors so I know I have good GPS signals in my area.

Is there some changes I can make that may improve their performance?

Larry

5

How close is the nearest base station of your NTRIP service?

6

L1 RTK is in general very sensitive to antennas, you can look at this piece by T.Takasu about how important it is. Stock antennas are decent, they are small and fit many applications, but you can get an improved one.

1 Like
7

I have the same problem using reach like base and rover with stock antennas,the antennas are separate only a few meters, I only see “fix” sporadically. My setup is GPS+GLONASS 5Hz, with Galileo nothing work.

8

It’s about 1 km.

9

Another guess, can you try with GPS only?

10

Good guess, thanks for your help.
Trying with GPS only, I managed to get fix. It wasn’t stable: in a several minutes test, I got three fix and three float.
Anyway, that’s an improvement. I also have to admit that today is quite cloudly, I suppose this may interfere. Then, what’s the problem with GLONASS? In the ntrip server page, they said the service is GLONASS compatible.
Another question: why with different fixes I got two very different positions (one about 60 cm distant from the other)? In the attached image, 1st and 3rd fix I got refer to the origin of the graph, while the second one is at coordinates ~ (-30,+50) [cm]

fix&float.png1905×1115 71.7 KB

11

Glonass is tricky for RTK because of the inter-channel biases. All satellites transmit on slightly different frequencies (compared to GPS or Beidou) and that results in receiver-specific delays in the front-end. Ability to get fixes with glonass might depend on the receivers in use. It is best to use Glonass ambiguity resolution when using a pair of Reaches. You can also use Glonass satellites, but not include them in AR by opening “advanced settings” and changing “GLONASS integer ambiguity resolution mode” to “off”.

You can have shift in fixed solution because of multipath, are you using a large metal ground plane under the antenna?

2 Likes
12

Yes, 200x100 mm iron in this specific case. I also ordered some copper sheets, I read that this might help.

13

Sometime grey bars disappear for few seconds and the solution remain fix or float. Any idea why this occurs?

14

How often does this occur? This might be due to delays in the connection to the NTRIP service

15

Like every 30 seconds, for 4-5 seconds each time.