Gnss monitor

Experiments to extract and display GNSS live or recorded data

Screenshot

Left: Satellite movement in the sky above. Mid: Reported movement of the stationary antenna. Right: Number of tracked satellites over the last ~20 hours.

Required packages

Some of the packages are merely for convenience, but most are required to run the intended applications.

libreadline-dev
libopencv-dev
libgpiod-dev
gpiod
cmake
subversion
aptitude
apt-file
telnet
ntp
ntpdate
nmap
lsof
libpaho-mqtt-dev 
libpaho-mqttpp-dev (if not available, then not needed)
python3-paho-mqtt
python3-opencv
python3-setproctitle
mosquito
mosquitto-dev 
mosquitto-clients
libusb-dev
libcli11-dev    (maybe not available)
libgeographiclib-dev
libpaho-mqttpp-dev
qt6-base-dev
qt6-tools-dev
libxkbcommon-dev
sudo apt install libreadline-dev libopencv-dev libgpiod-dev gpiod cmake subversion aptitude apt-file telnet ntp ntpdate nmap lsof python3-paho-mqtt libpaho-mqtt-dev python3-opencv python3-setproctitle mosquitto mosquitto-dev mosquitto-clients libusb-dev libcli11-dev libgeographiclib-dev libpaho-mqttpp-dev qt6-base-dev qt6-tools-dev libxkbcommon-dev

For Python install

pip install geographiclib

or

sudo apt install python3-geographiclib

Build

Code is found here (on SVN)

svn co svn://repos.gbar.dtu.dk/jcan/svnjca/projekter/gnss_receiver

The C++ code is then in qt/gnss_qt

Build by

cd gnss_receiver/qt/gnss_qt
mkdir -p build
cd build
cmake ..
make -j3

Debug build by

cd gnss_receiver/qt/gnss_qt
mkdir -p build
cd build
cmake -DCMAKE_BUILD_TYPE=Debug ..
make -j3

Run once to create a configuration file, then edit to configure.

./gnss_qt
nano gnss_qt.ini

Debug run with valgrind

valgrind ./gnss_qt

CMake problem

GeographicLibConfig.cmake

The find package

find_package(GeographicLib REQUIRED)

in cmake fails, as the file GeographicLibConfig.cmake is not found.

This can be fixed by renaming the provided file FindGeographicLib.cmake by

cd /usr/share/cmake/geographiclib
sudo ln -s FindGeographicLib.cmake GeographicLibConfig.cmake

XKB

Missing library, and CMake complains:

-- Could NOT find XKB (missing: XKB_LIBRARY XKB_INCLUDE_DIR) (Required is at least version "0.5.0")

The solution was to install

sudo apt install libxkbcommon-dev

This occurred on Raspberry Pi 4-5 using the 64-bit default OS.

XCB-plugin

When trying to start the Qt app on reboot I got:

Could not load the Qt platform plugin "xcb" in "" even though it was found.

I inserted

export QT_QPA_PLATFORM=xcb

into the 'on_reboot.bash' that is activated by crontab on reboot.

and installed

sudo apt install qt5dxcb-plugin

No, it didn't help. Use desktop-file

Autostart QT-GUI app at boot

Make a desktop file in ~/.config/autostart/

cd 
cd .config
mkdir -p autostart
cd autostart
nano qt_monitor.desktop

Insert the following

[Desktop Entry]
Name=Gnss_qt
Exec=/home/local/on_reboot.fromDesktop
Type=Application
Terminal=true
NoDisplay=false
X-KeepTerminal=true
StartupNotify=true

The file /home/local/on_reboot.fromDesktop is an executable bash script with the following content;

#!/bin/bash
# script to start applications after a reboot
#
cd /home/local/svn/weather_monitor/qt_monitor/build
./gnss_qt -d 2>out_err.txt >out_console.txt 

Some of the entries, like X-KeeepTerminal seems not to work.

Configure

After the gnss_qt is run the first time, there should be a default configuration file

[service]
logpath = log_%d/
; the '%d' will be replaced with date and timestamp (must end with a '/'). = 
max_logging_minutes = 60.0
log_service = true

[mqttin]
broker = tcp://localhost:1883
context = ublox9/
clientid = ublox9_in
function = nmea/
system = ublox9/
log = true
print = false
use = false

[gnss]
;input = /dev/ttyACM0
input = ../../../log/log_24h_asta_mqtt.txt
input_use = true
log = false
interval_sec = 0
logtime = false

[ini]
; set 'saveconfig' to 'false' to avoid autosave = 
saveconfig = true
version = 2285 2025-06-26 07:20:46

[mqttinw]
broker = tcp://192.168.2.216:1883
context = not used
clientid = weather_in
function = 
system = weather7/
log = true
print = false
use = true

Each group corresponds to one of the modules in the app:

• Group [gnss]. Input can be from a file, either directly from the receiver /dev/ttyACM0, or a logfile generated by the MQTT streamer for NMEA messages. Set input_use = true to use this alternative.
• Group [mqttin]. It is for use with an MQTT server that streams the NMEA messages. Change the IP in the [mqttin] group and change to use=true. The NMEA messages are assumed to be in the payload of the message, and the subject as described (subscribing to 'ublox9/nmea/#').
• Group [mqttinw] is the input source for weather information.