Overview

This article applies to both GP-Cloud-based anomaly detection algorithms and the onboard signal processing (OSP) algorithms in GP-Probe DIN L1. If your probe is triggering anomaly events too frequently in an open area where you expect minimal interference, this guide will help you understand potential causes and solutions.



Common Causes of High False-Positive Rates

Common factors increasing false-positive anomaly detections:

  • Industrial noise from nearby electronic equipment (Wi-Fi routers, Bluetooth devices, CCTV cameras, computers, etc.)
  • Limited sky visibility 
  • Lack of spectrum normalization and anomaly algorithm calibration


If your GP-Probe DIN L1 reports excessive anomaly detections in environments where interference is unlikely, ensure you have followed these best practices:

1. Ensure Your GP-Probe is Running the Latest Firmware

Before proceeding with troubleshooting, make sure that your GP-Probe DIN L1 is running the latest firmware version. Firmware updates include important bug fixes and optimizations for anomaly detection.

Follow this guide to update your probe's firmware:
How to Update GP-Probe's Firmware


2. Proper GNSS Antenna Placement

2.1 Avoid industrial noise sources:
Electronic devices such as Wi-Fi routers, Bluetooth equipment, computers, and CCTV cameras generate electromagnetic noise, which can trigger false detections. Industrial noise often occurs around the 1.6 GHz band due to harmonics from commonly used oscillators (e.g., 40 MHz, 80 MHz).


Example: Below are two screenshots illustrating the difference between a clean environment and one affected by industrial noise.

  • Clean spectrum (low false detections):
  • Industrial noise detected (high false detections):

2.2 Ensure an unobstructed view of the sky:
Antennas placed in areas with limited sky visibility (e.g., indoors, under trees, or near buildings) can experience fluctuations in the signal-to-noise ratio (SNR), leading to anomalies.

  • Open-sky installation: SNR is stable, with low residuals and good dilution of precision (DOP):
  • Windowsill installation: Large SNR fluctuations, spikes in residuals, and poor DOP:


2.3 Avoiding Signal Reflections (Multipath Effects)

Reflected GNSS signals can trigger anomaly detection algorithms. To minimize multipath effects:

  • Avoid installing antennas near tall buildings.
  • Use high-quality antennas with backside lobe suppression to prevent reflections from the ground.

2.4 Using a Low-Loss RF Cable

Cable Recommendations:

  • RG58: Maximum length of 30 meters.
  • LMR400: Maximum length of 70 meters.
  • The average SNR should be at least 30 dB for stable performance.


3. Spectrum Flatness Normalization and Calibrating Detection Algorithms

To improve anomaly detection accuracy, you should do Spectrum Flatness Normalization and calibrate the detection algorithms.


3.1 Accessing the Configuration Panel

To perform these steps, you must first access the Web Configuration Panel of your GP-Probe DIN L1. If you are unsure how to do this, follow the guide below:
How to Get Access to Configuration Panel


3.2 Spectrum Normalization

  1. Log into the Web Configuration Panel
  2. Navigate to Status > Measurements.
  3. Locate the Power Spectrum graph and click "Spectrum Normalization" to align the spectrum flatness, compensating for antenna and preamplifier distortions:


3.3 Onboard Anomaly Detection Calibration 

Whenever you move your GP-Probe, change antennas, or replace RF cables, recalibrating the anomaly detection algorithms is crucial to ensure accurate detection.

  1. Allow the device to collect data for at least 5 minutes.
  2. Click "Calibrate Anomaly" next to the Anomaly graph to initiate calibration.


3.4 Calibrating Anomaly Detection in GP-Cloud

  1. Open the Probe Config Popup from the Map, Charts, or Probes menu.
  2. In the Algorithms Calibration section, press "Reset Calibration":


⚠ Important: Perform calibration only in a clean RF environment. If interference is present, the system may incorrectly classify interference as normal, leading to false detections when conditions change. Full calibration takes up to 24 hours, but sensitivity improves gradually during this period.

Full calibration guide:
GP-Probe Calibration

What to Do if the Issue Persists?

If you have implemented the above recommendations and still experience high false-positive rates, contact our technical support team with the following information:

  1. Photos of the antenna installation site.
  2. Screenshots from GP-Cloud or the Web Configuration Panel showing excessive anomaly detections.
  3. Raw measurement data (if using onboard detection with OSP option).


To assist our engineers, you can enable the STREAM option to capture raw GNSS data for postanalysis:

  • Activate the STREAM License in Admin/Licenses.

If you do not have a license for the Stream option, please contact technical support and we will provide it for the necessary period of time to troubleshoot the issue.

  • Enable STREAM in Connection Config > Stream Enable.
  • Record data via the Status/Measurements page:
  • Submit the recorded file to our support team for analysis.


For detailed instructions on enabling STREAM, visit:
How to Enable Raw Data Streaming on GP-Probe DIN L1



By following this guide, you can significantly reduce false-positive anomaly detections and improve the reliability of your GP-Probe DIN L1.