A remote pilot is preparing for a construction documentation mission. The nearest weather station reads 9 knots of surface wind. Observing the tree line along the property, the pilot notices upper branches swaying vigorously while lower foliage is relatively still. What is the most accurate interpretation?
Why →Wind gradient describes the phenomenon where wind speed increases with altitude as surface friction from terrain, buildings, and vegetation slows the wind near the ground. Vigorous upper branch movement with calm lower foliage is a visual indicator that wind speeds aloft are substantially higher than the surface measurement. At typical drone altitudes the actual wind can be well above the surface reading.
The trap →Surface readings routinely understate conditions at altitude, and over-trusting them is a known contributor to flyaways. The gusting-only answer invents a distinction the tree line cannot actually show you.
Field note →Watch the tree line at different heights before launch: upper branches moving much more than lower ones means add a mental multiplier for your operating altitude. Manufacturer wind specs assume clean air; gusty gradient conditions near obstacles are worse.