6.70 GNSS Global Navigation Satellite System

6.70.2 Explain the limitations of using GPS/GNSS to supplement normal visual navigation.

While GPS/GNSS is a useful navigation aid, it cannot replace visual navigation. Its limitations include

Signal Reliability

• Blocked or degraded signals in mountainous terrain, dense forests, or urban areas.
• Multipath errors from signals reflecting off buildings or terrain.
• Atmospheric disturbances (ionosphere/troposphere) affecting accuracy.

Accuracy Limitations

• Typical civilian GPS is accurate to 3–10 meters, which may not suffice for close maneuvering.
• GNSS errors, though usually small, can accumulate over time.

Latency / Update Rate

• Standard receivers may update only once per second (1 Hz), introducing a slight lag in position at high speeds.

Equipment Dependence

• Requires functional electronics and power. Failures can leave pilots without GPS assistance.

No Traffic Awareness