Low Interference

A low interference site is any location where the sky above you is largely unobstructed and the surrounding terrain does not significantly disrupt GPS signals. These are the most forgiving sites you will fly. The defining characteristic is space — signals you receive are almost entirely direct line-of-sight from satellites, which is exactly what GPS is designed around.

Key Rule

The most straightforward site type. Focus on wind and light conditions rather than GPS. Low interference does not mean zero risk — environmental factors like sea breeze and power lines can still catch you out.

Low interference environments exist wherever human development is low-rise and spread out, or wherever natural open space dominates. GPS signals travel in straight lines from satellites 20,000 km above Earth. Any object between a satellite and your aircraft either blocks that signal entirely or reflects it, creating a degraded or false position reading.

Parks and reserves — wide sky view, minimal reflective surfaces, grass absorbs rather than reflects radio signals
Industrial estates on city fringe — large flat footprints, single-storey warehouses, wide access roads, little vertical structure
Cemeteries — consistently among the cleanest GPS environments in urban areas: open, flat, low monuments, positioned away from dense development
Rural and open areas — best-case GPS environment with full hemisphere satellite access

Recommended Time Windows

06:30 – 09:00 — ✅ Optimal — best satellite geometry + golden hour light + low foot traffic

09:00 – 15:30 — ⚠️ Acceptable — flat harsh light, slightly degraded GPS midday, manageable

15:30 – 17:30 — ✅ Good — afternoon golden hour, GPS still reliable, wind often building at coastal sites

After sunset — 🚫 Do Not Fly — no authorisation, no visual reference

Primary Failure Mode

Environmental, not technical. Coastal sea breeze builds faster than expected. Power lines missed in planning become obstacles during return-to-home. The GPS environment cooperates — the weather doesn't always.

Knowledge Check

1. What is the primary variable to manage at a low interference open site?

2. Why do cemeteries have consistently clean GPS environments?

3. What is the primary failure mode at low interference coastal sites?

4. How long does satellite acquisition typically take at a low interference site?