The ValidWind™ system employs an XL200 laser rangefinder to track small, lightweight, helium-filled balloons
(0.33 meters, 0.015 kg). We record their trajectories (range resolution 0.5 meters) and automatically produce local
wind profiles in real time. Tracking range is enhanced beyond 2 km by applying retro-reflector tape to the balloons.
Aerodynamic analysis shows that ValidWind balloon motion is well coupled to the local wind within relaxation
times ~ 1 second, due to drag forces at subcritical Reynolds numbers Re < 2×105. Such balloons are Lagrangian
sensors; i.e., they move with the wind as opposed to being fixed in space. In a field campaign involving many
balloons, slight variations in ground level winds at launch lead to trajectory patterns that we analyze to derive 3D
maps of the vertical and horizontal wind profiles downwind of the launch area. Field campaigns are focused on
likely sites for wind power generation and on facilities from which airborne particulates are emitted. We describe
results of wind measurements in Utah near the cities of Clarkston, Logan, and Ogden. ValidWind is a relatively
inexpensive wind sensor that is easily and rapidly transported and deployed at remote sites. It is an ideal instrument
for wind prospecting to support early decisions required, for example, in siting meteorology towers. ValidWind
provides high-resolution, real time characterization of the average and changing 3D wind fields in which wind
power turbines and other remote sensors must operate.