Lecture - coordinate system and projections.pptx

coordinate system and projections.pptx

1. 1. Geodetic Datum Also known as horizontal datum Defines the relationship between the physical earth and horizontal coordinates such as latitude and longitude 2. Vertical Datum The zero surface from which all elevations/heights are measured. Defines level surfaces. Types of Datum

2. NAD27 (North American Datum of 1927) uses the Clarke (1866) ellipsoid. NAD83 (North American Datum of 1983) uses the GRS80 ellipsoid. WGS84 (World Geodetic System of 1984) used GRS80. Presently uses the EGM 96 (Earth Gravitational Model 1996). North American Vertical Datum of 1988 (NAVD88). NAVD88 is now the reference vertical datum for elevation readings in North America. Types of Datum