Rangefinding

Rangefinding is the process of determining the distance from an observer or instrument to a target or object. It uses physical principles such as geometry, time, and wave propagation to estimate distance. Common approaches include triangulation, time-of-flight measurements, and phase shift techniques, and these can be implemented with optical, acoustic, or radio signals.

Triangulation measures distance by combining two lines of sight from known positions; time-of-flight sends a signal and measures travel time; phase-shift techniques compare the phase of a modulated or continuous signal. Other methods include structured light and lidar, which project patterns or pulses and compute distance from their deformation or return timing.

Technologies range from laser rangefinders, which emit short pulses or continuous beams, to radar and sonar systems. Ultrasonic rangefinders are common in robotics and consumer devices. Rangefinders are used in photography for focusing, surveying and construction for layout, navigation and mapping, sports such as golf for distance measurements, and in military and hunting for targeting and range estimation.

Accuracy depends on the method, range, and target reflectivity. Shorter ranges with highly reflecting targets tend to be more precise; adverse weather, atmospheric conditions, angle of incidence, and multi-path reflections can degrade measurements.

Rangefinding has origins in surveying and artillery and has evolved with advances in optics and electronics. Modern rangefinding devices are widespread across military, industrial, scientific, and consumer applications, enabling distance measurement with varying tradeoffs between speed, precision, and range.