GNSS Quality Assurance
What is GNSS Quality Assurance for?
Global Navigation Satellite Systems (GNSS) positioning and timing services form the backbone of many applications and markets. Civilian GNSS services are free of charge and globally available but insufficiently protected against unintentional and even intentional disturbances. OHB Digital Solution researches for more than 20 years on how to provide means to monitor and augment the GNSS services with GNSS quality assurance. For many applications, it’s not only precision that matters, but predominantly integrity too! Our knowledge and experience in GNSS quality assurance are available in many different forms in our GIDAS product family.
Jamming & Spoofing
GNSS is globally and freely available, but vulnerable to many threats. The signals transmitted from GNSS satellites orbiting the earth at approximately 20.000 km altitude above the earth’s surface are very weak with the transmission power of a 100W light bulb (depending on the constellation and satellite generation). The signals are received on the earth’s surface with a signal power below the thermal noise floor. These weak signals can be disturbed or degraded by many sources. The main classifications of local interferences are:
- Out of band interference and unintentional interference
This type of interference can be caused by services using neighboring frequency bands or environmental influences (e.g., GNSS multipath). It usually occurs in the vicinity of other infrastructure using radio frequency links.
The intentional attempt to interrupt the GNSS service by broadcasting higher-powered signals. With the discontinuation of GNSS positioning, the onboard system must fall back to alternative navigation systems. Especially during challenging conditions, this can raise the likelihood of accidents.
The intentional attempt to force a GNSS receiver to a false position/course can be challenging to detect. Spoofed GNSS receivers output false position and timing information, exposing the chance of collisions with the ground or other objects.
The first step in protecting your GNSS-dependent applications or platforms is to monitor the GNSS signal health on-location in real-time. While systems such as space-based augmentation systems (SBAS) or country-wide monitoring systems are typically designed to monitor the constellation health status (orbit-, satellite-clock-, uplink-errors), local interference or local anomalies are not visible. Especially for safety-critical applications, it is vital to monitor the GNSS signals and services as close to the application as possible.