Classic setup: observer at two points on level ground, different distances from a tower, measuring different angles of elevation. Let h = height, d = closer distance, D = farther distance. tan(alpha) = $\frac{h}{d}$, tan(beta) = $\frac{h}{D}$. If D - d is known, solve the system. Key formula: h = d*tan(alpha) = (d+L)*tan(beta) where L is the distance between observation points.