Receiving RTK RCTM Correction Data when Two Rover GPS are Plugged into Different Computers

GPS/GNSS Development Boards
1

I have purchased and am working with three GPS-RTK-SMA Breakout - ZED-F9P (GPS) units. I am using them in a system where one GPS is a base station and two GPS units are rovers. I have set this system up using your RTK base station and rover guide. I have linked the GPS website and the guide website below for your reference.

Due to the requirements of my system, I have each GPS plugged into a different computer. In this configuration, I have had trouble receiving RTCM correction data on the rovers from the base station. Here’s what I have troubleshooted:

Let’s say the three computers are computer 1, computer 2, computer 3, and the GPS units are base station, rover 1, and rover 2.

To recap, there is an RTK LED on the GPS PCB. It is illuminated when it is not receiving RTCM correction data, it blinks when it is receiving some data (float mode), and it turns off when it has received enough data to reach maximum accuracy (fixed mode).

Scenario 1 (this is what my system requires, and it is not working properly):

The base station is plugged into computer 1. Rover 1 is plugged into computer 2. Rover 2 is plugged into computer 3. The RTK LED on both rovers is green (not receiving RTCM correction data).

Scenario 2:

The base station is plugged into computer 1. Rover 1 and rover 2 are plugged into computer 2. The RTK LED on both rovers starts to blink and eventually shuts off (receiving RCTM correction data, starting in float mode, and finishing in fixed mode).

Scenario 3:

The base station is plugged into computer 1. Rover 1 is plugged into computer 2. The RTK LED on the starts to blink and eventually shuts off (receiving RCTM correction data, starting in float mode, and finishing in fixed mode).

Scenario 4:

The base station is plugged into computer 1. Rover 1 is plugged into computer 3. The RTK LED on the starts to blink and eventually shuts off (receiving RCTM correction data, starting in float mode, and finishing in fixed mode).

Scenario 5:

The base station is plugged into computer 1. Rover 2 is plugged into computer 2. The RTK LED on the starts to blink and eventually shuts off (receiving RCTM correction data, starting in float mode, and finishing in fixed mode).

Scenario 6:

The base station is plugged into computer 1. Rover 2 is plugged into computer 3. The RTK LED on the starts to blink and eventually shuts off (receiving RCTM correction data, starting in float mode, and finishing in fixed mode).

Based on this situation, would you be able to help me so that in scenario 1, the two rovers can receive RTCM correction data?

GPS: https://www.sparkfun.com/products/16481 … pcQAvD_BwE

RTK Guide: https://learn.sparkfun.com/tutorials/se … over-setup

2

Thanks for the detailed description, really makes understanding your setup much easier! How are you doing RTCM transport? Telemetry radio, LoRa, IP based, etc…?

3

I’m doing a wired connection at the moment. I have one wire connecting the base station GPS TX port to rover 1 GPS RX port and a second wire connecting the base station GPS TX port to rover 2 GPS RX port. Wire 1 and wire 2 are connected at the base station GPS TX port. All ports mentioned are the ones designated for RTCM.

4

On a Windows box you should be able to run uCenter Classic, and have the it run it’s internal NTRIP Server, which it can share with other computers on your network with suitable windows firewall settings, or other instances of uCenter Classic in NTRIP Client mode connecting to 127.0.0.1.

Other machines can run uCenter Classic’s NTRIP Client.

More broadly you could look at SNIP and RTK2GO

5

The base station GPS is plugged into a Windows computer while the two rovers must be plugged into Linux computers. The Linux computers are raspberry pi’s running Ubuntu 20.04. My application requires this operating system. Unfortunately, I haven’t been able to get any form of uCenter to run on the raspberry pi’s.

6

Hi,

Take a look at PyGPSClient: https://github.com/semuconsulting/PyGPSClient . It could be a good solution for you - on RPi.

I hope this helps,

Paul

7

You shouldn’t need uCenter on the RPi, should just need to run a suitable NTRIP Client to push the RTCM3 packets into the receiver.

A simple app on Linux connecting to the associated /dev/tty should allow you to interact with the ZED-F9P

8

I recommend STRSVR from within rtklib (https://www.rtklib.com/) - it’s a great app to gather data in from various sources (serial, NTRIP Client, etc) and send it to various places (a different serial port, NTRIP Server, etc). We document its use here: https://learn.sparkfun.com/tutorials/ho … ster-setup (Search STRSVR).