Adding GPS Signal Fix Status to Grafana with Telegraf and InfluxDB

John Burns

If you’re running a Raspberry Pi-based time server or GPS-equipped system and want visibility into the GPS signal status (2D, 3D fix, or no lock), you can use a simple Bash script and Telegraf to bring that data into your InfluxDB time series database — and visualize it in Grafana.

In this post, we’ll walk through how to:

  • Create a lightweight GPS fix monitoring script
  • Use Telegraf’s inputs.exec plugin to ingest the data
  • Store it in InfluxDB
  • Visualize GPS lock status in Grafana

🚀 Why Monitor GPS Fix Status?

When using GPS for time synchronization (especially with chrony or ntpd), it’s useful to know whether the GPS module actually has a signal lock:

  • No lock = No reliable time source
  • 2D fix = Partial satellite coverage
  • 3D fix (locked) = Full GPS fix — ideal for timekeeping

You can surface this data with a simple integration between gpsd, gpspipe, and Telegraf.

🔧 Step 1: The GPS Fix Monitoring Script

Create a Bash script to run gpspipe and parse the signal fix mode:

#!/bin/bash

# Read 10 messages from gpsd in JSON format
GPS_OUTPUT=$(gpspipe -w -n 10 2>/dev/null)

# Determine GPS lock status from "mode" field
if echo "$GPS_OUTPUT" | grep -q '"mode":3'; then
    STATUS="LOCKED"
elif echo "$GPS_OUTPUT" | grep -q '"mode":2'; then
    STATUS="2D"
else
    STATUS="NOLOCK"
fi

# Output in InfluxDB line protocol
echo "gps_status status=\"$STATUS\""

Save it as /usr/local/bin/gps_status.sh and make it executable:

chmod +x /usr/local/bin/gps_status.sh

📡 Step 2: Configure Telegraf to Use the Script

Edit your telegraf.conf and add the following section:

[[inputs.exec]]
  commands = ["/usr/local/bin/gps_status.sh"]
  timeout = "5s"
  interval = "60s"
  data_format = "influx"

This tells Telegraf to:

  • Run the script every 60 seconds
  • Expect output in Influx line protocol (e.g., gps_status status="LOCKED")
  • Forward that data to InfluxDB

Restart Telegraf:

sudo systemctl restart telegraf

📥 Step 3: Verify InfluxDB is Receiving Data

Use the Influx CLI or query it from Grafana:

SELECT * FROM "gps_status" ORDER BY time DESC LIMIT 5

You should see something like:

time                status
----                ------
2024-04-02T12:00:00Z  LOCKED
2024-04-02T11:59:00Z  2D
2024-04-02T11:58:00Z  NOLOCK

📊 Step 4: Create a Grafana Panel

In Grafana:

  1. Create a new dashboard and add a Stat or Table panel.

  2. Set the data source to InfluxDB.

  3. Use a query like:

    SELECT last("status") FROM "gps_status"

  4. Set value mappings:

    • LOCKED → ✅ Green
    • 2D → ⚠️ Yellow
    • NOLOCK → ❌ Red

You now have a live GPS lock status display on your dashboard!

✅ Summary

This small script and Telegraf integration lets you monitor GPS status in real time, with no Python or heavy dependencies — just Bash, gpsd, Telegraf, and InfluxDB.

It’s a great fit for Raspberry Pi-based time servers or GPS tracking systems where knowing the GPS fix status is critical for reliability.

Thanks for reading! If you have questions or want to expand this to include other gpsd metrics, let me know!


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