nonGPS

NonGPS refers to methods and technologies used to determine position, movement, and navigation without relying on Global Positioning System signals. It encompasses sensor-based techniques and alternative positioning systems that operate in GPS-denied environments, such as indoors, underground, or in urban canyons. Some approaches may supplement GPS when available by using other satellite navigation systems, but non-GPS generally indicates methods that do not depend on US GPS alone.

Common non-GPS approaches include inertial navigation and dead reckoning, which use accelerometers and gyroscopes to estimate motion from a known starting point, though they suffer from accumulating error over time. Visual odometry and visual-inertial navigation combine cameras with IMUs to estimate motion and orientation. Lidar- or radar-based SLAM builds maps of the environment while localizing the device within it. Radio-based localization uses cellular networks, Wi-Fi networks, or Bluetooth beacons to estimate position, often via trilateration or fingerprinting. Ultra-wideband beacons can offer higher accuracy in some settings. Magnetic-field mapping and other environmental signatures can also assist positioning when other signals are weak.

Applications include indoor navigation in large buildings, warehouses, and museums; robotics and autonomous vehicles operating in GPS-denied areas; underground exploration, mining, and underwater contexts where satellite signals are unavailable. Many systems employ sensor fusion to combine multiple inputs for greater robustness and accuracy.

Limitations commonly include drift in inertial methods, infrastructure requirements for fingerprinting or beacon-based systems, and higher energy and computation demands. Accuracy varies widely by method and environment, from meter-scale in some Wi‑Fi or magnetic systems to centimeter-scale with carefully deployed UWB or LiDAR-based SLAM in controlled spaces. Related topics include inertial navigation, SLAM, indoor positioning, and visual odometry.