Explain different coordinate systems used in surveying.

Coordinate systems: Geographic coordinates (latitude, longitude) on earth's surface using ellipsoid. Projected coordinates (eastings, northings) on flat surface - UTM divides earth into 60 zones with Transverse Mercator projection. Local grid systems for specific regions. Vertical datums reference elevations - MSL in India, geoid models for GPS. WGS84 is global datum used by GPS. Transformations between systems use 7-parameter Helmert transformation. Survey-grade work requires understanding datum shifts - can exceed 200m between different datums. India uses Everest ellipsoid for topographic maps.