rangefinders

A rangefinder is a device that measures the distance from the observer to a target. Rangefinders are used in photography, surveying, construction, hunting, golf, and military contexts, and they employ different technologies and form factors.

The main methods include optical triangulation rangefinders, which estimate distance by parallax between two images or through a fixed baseline, and electronic rangefinders that emit signals such as laser light or radio waves. Laser rangefinders use time of flight or phase shift to compute distance, offering fast, precise measurements over short to long ranges. Radar rangefinders use radio waves and can cover longer distances or operate through certain obstructions. There are also rangefinder devices integrated into cameras, riflescopes, or binoculars.

Applications include photography, where rangefinders aid focusing in rangefinder cameras; golf, where portable devices provide distance to targets, sometimes with slope compensation; surveying and construction for site measurement and layout; hunting and military uses for targeting and reconnaissance; and industrial systems for automated measurement and safety.

Accuracy and limitations vary by technology and target characteristics. Short-range laser devices can achieve precision of millimeters to centimeters, while longer-range or radar devices may have larger errors. Accuracy is influenced by target reflectivity and geometry, weather, lighting, and line of sight. Some models require direct visibility to the target and can be affected by glass, rain, fog, or dense foliage.

History and development show a progression from optical triangulation and coincidence methods in the 19th and early 20th centuries to laser-based, compact digital rangefinders in the late 20th century and beyond. Modern rangefinders often integrate imaging, data linking, and digital readouts.