What is GPS and how is it used in surveying?

GPS (Global Positioning System) is a satellite-based navigation system that provides position and time information anywhere on Earth. In surveying, GPS receivers measure signals from multiple satellites to calculate precise coordinates. Applications include: establishing control points, topographic mapping, construction layout, vehicle tracking, and GIS data collection. Different GPS techniques (autonomous, DGPS, RTK) provide varying accuracy levels from meters to centimeters.