Coordinate types Potential field based coordinates Astronomical latitude and longitude Orthometric heights(heights measured about an equipotential surface, nominally mean-sea-level (MSL) Geometric coordinate systems Cartesian xYZ Geodetic latitude, longitude and height 02/803 12540Lec04 Astronomical coordinates Astronomical coordinates give the direction of the normal to the equipotential surface Measurements Latitude: Elevation angle to North Pole(center of star rotation field Longitude: Time difference between event at Greenwich and locally02/18/03 12.540 Lec 04 3 Coordinate types – – Orthometric heights (heights measured about an (MSL) – Cartesian XYZ – Geodetic latitude, longitude and height • Potential field based coordinates: Astronomical latitude and longitude equipotential surface, nominally mean-sea-level • Geometric coordinate systems 02/18/03 12.540 Lec 04 4 Astronomical coordinates – Latitude: Elevation angle to North Pole (center of star rotation field) – Longitude: Time difference between event at Greenwich and locally • Astronomical coordinates give the direction of the normal to the equipotential surface • Measurements: 2