Site Survey & Ground Hazards
~10 min read · Survey obstacles, people, security and privacy before committing to a site.
The site survey is where a mission stops being a map exercise and becomes a physical place with wires, people, RF noise, and neighbors. The exam folds it into 107.49: assessing the operating environment is not optional preparation — it is a required preflight action.
Ground hazards
Walk or study the site for: powerlines and guy wires (nearly invisible from the air and on satellite imagery — assume every pole connects to every other), towers and antennas (RF interference plus physical obstacle), trees on approach lines, water bodies (no forced-landing option), moving machinery, and livestock or wildlife (birds of prey attack drones). Identify launch/recovery zones with clear sightlines and an emergency landing area reachable from anywhere on the route.
- Wires: the signature drone killer — assume more than you can see
- Plan primary and emergency landing zones before launch
- Satellite imagery ages; verify on site
People, access, and security
Part 107 bars sustained flight over people outside the category system, so the survey must map where people are and will be: workers, pedestrians, spectators the operation itself will attract. Control the area where practical — cones, briefed escorts, timing around shifts. Security also protects the crew and equipment: unattended gear, hostile bystanders, and traffic near the control station are all survey items. On someone's property, secure landowner permission; airspace is the FAA's, but launch points are not.
- Map static and predictable people flows; plan for onlookers
- Barriers/escorts convert open areas into controlled ones
- Landowner permission for launch/recovery sites
Privacy and RF environment
Privacy is mostly state/local law, but professional practice — and the FAA's guidance — expects avoiding gratuitous imaging of private spaces: adjust camera angles, notify neighbors for close work. The RF environment decides link quality: high-voltage lines, broadcast towers, dense Wi-Fi, and metal structures degrade command and GPS links — anticipate multipath near large buildings and plan tighter VLOS margins where interference is likely.
Worked example
Tomorrow you map a construction site bordered by a school on one side and 138-kV transmission lines on another. Workers rotate at 3 p.m.; recess runs 12:00–12:45. Satellite imagery is 14 months old. Build the survey-driven plan.
Timing: fly outside recess (children concentrated outdoors next door = people you cannot control) and away from the 3 p.m. shift change (site-wide movement). The transmission corridor: physical obstacle plus RF/magnetic interference — plan flight lines that never require crossing under or between conductors, place RTH altitude above the lines, and expect compass/link degradation on that boundary. Stale imagery: walk the site on arrival — new crane, new stockpiles, new fencing are all likely. Launch zone: inside the fenced site with escort control, sightlines down every flight line, emergency landing areas at each grid corner away from the school side. That is 107.49 executed as a plan rather than a checkbox.
Common exam pitfalls
Planning entirely from satellite imagery.
Imagery is months-to-years old and hides wires entirely. The survey ends with eyes on the actual site.
Forgetting the people the operation attracts.
Spectators gather at drone operations. Plan containment for the crowd you create, not just the one you found.
Treating FAA authorization as full permission.
LAANC clears airspace only. Land access, local ordinances, and privacy expectations are separate boxes to check.
WELPS: Wires, Emergency zones, Landowner, People, Signals.
Recap
- Site assessment is a required 107.49 preflight action
- Wires and guy wires are the premier physical hazard
- Define launch, recovery, and emergency landing zones in advance
- Map people flows; control or time around them; expect onlookers
- Secure landowner permission; respect privacy norms and local law
- Anticipate RF/GPS degradation near towers, HV lines, and structures
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