Trouble maintaining RTK fix with Reach RS+ for Tractor Guidance

wilberttalen · November 2, 2018, 10:18pm

Hi I am having a few issues with my Reach RS+ Base/Rover combo that I am using for Tractor guidance with AgOpenGPS. I often seem to lose my RTK fix and end up in Float a fair amount. I am pretty sure it is in the RTCM3 settings in that I have too many selected and in how the Base coordinates are configured.

My needs are:

a constant realtime RTK fix at 5Hz
maximum base line of 2km
pass to pass accuracy of 2cm.

My questions for the community are:

Which RTCM3 messages should I have enabled and at what rate to maintain overall realtime RTK fix at 5Hz. I live on the East coast of Canada.
If I mount the base in the same spot every time, should I manually enter its position or is it best to let it average its position.
If I am doing an average of the Base coordinates what is the best Single, Float, or Fix
What should my minimum coordinate accumulation time be.

Firmware image 2.11.2 and ReachView version 1.4.

[details=“Simple system report”]

app version: 2.11.2-r0
'wifi_status, interface: wlan0':
- wifi_mode: ap
- access_point:
    band: bg
    channel: 1
    password: null
  ip: 192.168.42.1
  is_added: true
  is_connected: true
  mac_address: CC:B8:A8:F5:5F:8C
  security: wpa-psk
  ssid: ReachBASE:5f:8c
  uuid: fdd54840-8e1d-40dc-931b-9537536e87a8
base mode:
  base coordinates:
    accumulation: '4.6'
    antenna offset:
      east: '0'
      north: '0'
      up: '0'
    coordinates:
    - '0'
    - '0'
    - '0'
    format: llh
    mode: single-and-hold
  output:
    enabled: true
    format: rtcm3
    path: lora
    type: lora
  rtcm3 messages:
    '1002':
      enabled: true
      frequency: '5'
    '1006':
      enabled: true
      frequency: '0.1'
    '1008':
      enabled: false
      frequency: '1'
    '1010':
      enabled: true
      frequency: '5'
    '1019':
      enabled: false
      frequency: '1'
    '1020':
      enabled: false
      frequency: '1'
    '1097':
      enabled: false
      frequency: '1'
    '1107':
      enabled: true
      frequency: '1'
    '1117':
      enabled: false
      frequency: '5'
    '1127':
      enabled: false
      frequency: '1'
    gps:
      enabled: false
      frequency: '5'
    qzss:
      enabled: false
      frequency: '5'
bluetooth:
  discoverable: false
  enabled: false
  pin: '***'
correction input:
  input2:
    enabled: true
    format: rtcm3
    path: ttyMFD2:38400:8:n:1:off
    send position to base: 'off'
    type: serial
  input3:
    enabled: false
    format: rtcm3
    path: :9028
    type: tcpsvr
logging:
  base:
    format: RTCM3
    started: true
    version: null
  correction:
    format: RTCM3
    started: true
    version: null
  interval: 24
  overwrite: true
  raw:
    format: UBX
    started: true
    version: null
  solution:
    format: LLH
    started: true
    version: null
lora:
  air rate: '18.23'
  frequency: 908200
  output power: '20'
position output:
  output1:
    enabled: true
    format: nmea
    path: bluetooth
    type: bluetooth
  output2:
    enabled: true
    format: llh
    path: :9001
    type: tcpsvr
  output3:
    enabled: true
    format: llh
    path: :2014
    type: tcpsvr
  output4:
    enabled: true
    format: llh
    path: :2015
    type: tcpsvr
rtk settings:
  elevation mask angle: '15'
  glonass ar mode: 'off'
  gps ar mode: fix-and-hold
  max horizontal acceleration: '1'
  max vertical acceleration: '1'
  positioning mode: kinematic
  positioning systems:
    compass: false
    galileo: false
    glonass: true
    gps: true
    qzs: true
    qzss: true
    sbas: true
  snr mask: '35'
  update rate: '5'

Rover is mounted to the tractor cab roof.

Base is mounted on top of the tallest grain tank. There is potential that it may sway in the wind.

!
!

wizprod · November 3, 2018, 7:29am

Have you tried this?

wilberttalen · November 3, 2018, 9:14am

I have not tried that yet, nice platform. Do you think that vibration is the issue that causes fix to turn to float?

wizprod · November 3, 2018, 10:12am

At least according to this: Upgrade your Reach RS/RS+ with a vibration damping platform for smooth machinery guidance

Yasser_Arafat_Tuanad · November 3, 2018, 1:17pm

Since you are putting the base at the same location. you better input it manually so you can maintain a 2 cm pass to pass accuracy… The problem with averaging from time to time is there are shift of coordinates.

michaelL · November 4, 2018, 2:39pm

Looks pretty good. I manage construction machine control and first thing I would recommend is to raise the receiver off the cab more and put some kind of insulator pad underneath. Not underneath the mounting plate for vibration, but to shield the receiver from the metal of the cab.

dmitriy.ershov · November 5, 2018, 9:40am

Hi Wilbert,

Thanks for sharing system report and the photos of your hardware setup.

I’d recommend you do the following:

Update your units to the latest firmware
Try RTK settings and LoRa configuration from this video:

Post raw logs from base and rover so we can see if oscillations affect the solution

Thanks!

wilberttalen · November 7, 2018, 3:13am

Thank you
I upgraded to the latest firmware and I set things up exactly as the video suggested. I didn’t lose RTK fix once while driving the tractor. A question I have is how best to achieve the maximum Hz. In the video the rover is set to take GNSS at 5Hz while the base is putting out RTK corrections at 1Hz maximum.

Does this mean that my rover’s position is only being corrected via L1 once per second? If I am driving my tractor while mowing a field at 14 km/h 1Hz RTK is not sufficient. What would the best settings be for this use to maintain accurate guidance for auto-steering?

Another question I have is regarding a loss of RTK fix and then dropping down RTK float and then to GPS fix. What RTCM3 messages would be required so that there would be a DGPS fix before dropping to a GPS fix? I guess what I’m asking is if I don’t need cm level accuracy for a job but only 15-30cm level is there a way to achive a DGPS fix with only a rover (i.e. without base corrections)

wilberttalen · November 7, 2018, 3:18am

Thanks! So put it up higher for better satellite visibility? Have you noticed a big difference in using an insulator pad. There isn’t a whole lot of metal on the roof of tractor cabs these days anyway I’m just wondering what you use and how much difference it makes.

wilberttalen · November 7, 2018, 3:20am

So what’s the best setting to find the base’s actual position for later manual input. Average Single for 30 minutes?

todd1 · November 7, 2018, 4:23am

We have used them for machine control and vibrations can mess up the rover. We started mounting the rover in a pelican case (foam filled box) and they became much more reliable. I would suggest that is your issue looking at your mount

igor.vereninov · November 7, 2018, 8:22am

You can have corrections at 1Hz and update rate on rover at 5Hz. Software will handle the difference just fine. Corrections once per second are sufficient.

TB_RTK · November 7, 2018, 9:24am

Sorry for derailing the thread. Just remembered a situation with the RS (base and rover with 2.15.3 or later) using ntrip over RTK2GO. I dont think its a latency issue as the problem seemed to be on my local wifi as well.
Rover in RTK at 5hz with gps,glonass and sbas
Base runing at 5hz with rtcm outputing 1hz on gps,base coordinates, glonass and sbas

With base at 5hz rtk and 1hz rtcm messages , gps correction on rover is droping in and out. but not glonass.
When base changed to 1hz in rtk setting and 1hz rtcm message, the correction on rover is stable.

I could try record a session and post it next time around

system · February 15, 2019, 9:24am

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