GNSS Real‐Time Kinematic (RTK) - norlab-ulaval/Norlab_wiki GitHub Wiki

This guide explains how to set up Real-Time Kinematics (RTK) using the Emlid GNSS system on the Warthog robot with Emlid M2 receivers.

1. Turn on the breaker for the USB hub.
2. Ensure the USB cable is connected between:
   • The USB hub inside the Pelican case
   • The high-level computer

3. Verify the Emlid M2 LoRa radio modules are plugged in.
4. Ensure LoRa antennas are securely connected to each radio module.

• Connect to the warthog wifi
• Access to the reicevers' emlid interface: on Sturdy Steve there is a bookmark called emlid click on open all tabs.

http://192.168.3.205/ #front
http://192.168.3.204/ #right
http://192.168.3.203/ #left

• For the front, right and left receivers in the Emlid interface go to Correction Input then select LoRa radio with the following settings:

• Plug in the Radio antenna and put the aluminum extension at the bottom of the RS3. This should look like that once assembled.

• Power on the RS3 Base Station (holde the button until white light).
• Connect to the Reach RS3 Wifi (password: emlidreach) and access the Emlid interface:

http://192.168.42.1/ #RS3

• Go to Base Output and select LoRa radio, make sure that the frequency is the same as the receivers.
• Go to Base Settings and select Manual, set the antenna height and type measured height = 0.15. This correspond to the alumnium extension (0.15m).

The interface will add 0.134 (distance between the bottom of the antenna and the phase offset center) so the antenna height will be set to 0.284m.

• Set the base station coordinates to the one of the Pillar C you will put it on using [those coordinates]:

Long: -71.27459561 E
Lat: 46.77944318 N
Ellipsoidal height: 61.803 m

• Power off the Reach Rs3 and the breaker for the USB hub (receivers) inside the Pelican Case.

• Go outside with Warthog
• Put the RS3 with the extension on the Pillar C and Power it on. PS: You can find a drawing of where is the pillar here.

• Power on the USB breaker in the Pelican Case to start the receivers recordings.
• Connect to one of the emlid receivers and verify that the solution is set to FIX and not NONE. This means that the LoRa connection is working and the base station is sending corrections to the receivers.
• Then start recording your bag containing the /emlid topics.

The /emlid topics includes the /front, /left and /right topics each including /fix, heading, nmea_sentence topics. The fix is a NavSatFix message type containing the Latitude, Longitude and height coordinates of the receiver Using ros2 topic list | grep /emlid you should see something like this:

  /emlid/left/nmea_sentence
  /emlid/left/fix
  /emlid/left/heading
  /emlid/left/time_reference
  /emlid/left/vel
  /emlid/front/nmea_sentence
  /emlid/front/fix
  /emlid/front/heading
  /emlid/front/time_reference
  /emlid/front/vel
  /emlid/right/nmea_sentence
  /emlid/right/fix
  /emlid/right/heading
  /emlid/right/time_reference
  /emlid/right/vel

The nmea_sentence is Sentence message type containing the sentence according to the NMEA standard (mainly of type GGA) more info here.

• Now can you start with you experiment ✨

Power cycle the Emlid base receiver next to the Warthog. It automatically connects to the Warthog's wifi. Then, call this script:

download_emlid_logs.sh <YYYYMMDD> <output_dir>