# High precision GNSS tracking with portable size and budget price equipment - Savonia AMK

> This document reports on experimental testing of compact and budget-friendly GNSS RTK technology.

## Introduction
Traditionally, GNSS/RTK technology and commercial equipment have been expensive, quite large, and required a separate base station mounted on a tripod or an internet connection to a 3rd party service provider for RTK correction signals. Necessary electronics have been integrated into larger chassis, such as excavators or drones.

This article is devoted to the results of experimental testing of GNSS RTK (Global Navigation Satellite System, Real Time Kinematic), the purpose of which is to evaluate the accuracy when used in mobile high-precision tracking systems. Experiments are based on a fixed baseline cross-reference comparison.

## Operating Principle
The operating principle of the technology is to eliminate errors caused by signal propagation from the satellite. This error is calculated at a fixed point (the base station) and then transmitted to other receivers (rovers). Transmission of correction messages (RTCM) is possible through different channels, both directly (radio link wire) and via the Internet using the NTRIP protocol.

NTRIP defines three roles:
*   **Server:** Base station
*   **Client:** Rover
*   **Caster:** Web server

RTK2GO.com is a community-driven NTRIP caster that allows you to stream your base station and connect to any public base stations.

## Experimental Setup
For evaluation, we chose SimpleRTK2B boards based on u-blox chips. These boards feature modular communications plugins that allow us to test different deployment scenarios using 4G, Wi-Fi, and long- and medium-range radio.

To conduct the experiment, the receiver antennas were mounted on the roof of a car. Since they were always at a fixed distance from each other, the difference between the absolute values of coordinates and speed is an error.

Three rovers and two Base Stations participated in the experiment:
1.  The first receives corrections via Radio Link (RF).
2.  The second receives them from the same Base Station, but via the internet.
3.  The third rover receives them via the Internet, but from a publicly accessible Base station.

This architecture allowed for the comparison of signal quality depending on different factors: RTCM source and Base Station quality.

## Results and Conclusions
The distribution of inter-rover distance and speed, connected to the same base station, corresponds to the declared centimeter-level accuracy. The distance between three individual antennas is exactly seven centimeters.

We can conclude that:
1.  The method of transmitting corrections does not lead to signal degradation.
2.  The public base station showed some offset, although the distance and speed values are stable.
3.  Signals transmitted via the Internet are more robust because they do not require direct line of sight.

This experiment has shown that compact and relatively budget boards can provide high performance and centimeter-level accuracy. The size of the antennas and integrated electronics, as well as various communication capabilities, allow the technology to be used on smaller enclosures. Both integrated and portable use is viable depending on the application.

## Project Information
This work was carried out in the Automaatio ja Tekoäly – Tiedoksi (AuToTIE) project (EAKR / Pohjois-Savon liitto, A80154) in collaboration with PehuTec Oy.

### References
*   What is RTCM | u-blox (https://www.u-blox.com/en/technologies/rtcm)

### Authors
*   Nikita Toporkov, toporkov.nikita.01@gmail.com
*   Markku Kellomäki, markku.kellomaki@savonia.fi
*   Asmo Jakorinne, asmo.jakorinne@savonia.fi
*   Digicenter, Savonia-ammattikorkeakoulu

### Contributors
*   Mikhail Toporkov (3d modeling) – mihtop2005@gmail.com, Savon ammattiopisto
*   Niklas Etling (experiments assistance) – niklas.etling@gmail.com, Savonia-Ammattikorkeakoulu
*   Nikita Toporkov, Project Worker, Savonia University of Applied Sciences
*   Markku Kellomäki, Lecturer, Savonia University of Applied Sciences
*   Asmo Jakorinne, RDI Specialist, Savonia University of Applied Sciences