Geomatics and Measurement in Civil Engineering

LECTURE 2 (CH13)
SHAPE OF EARTH
 Shape is an ellipsoid
 Radius of equator is larger than at poles




o




 Geoid is a surface at msl, perpendicular to direction of gravity
 Ellipsoid is obtained by revolving ellipse around Earth's polar axis
 Ellipsoid:




o




FUNDAMENTALS OF GEODESY
 Deals with measurement and representation of Earth
 Major disciplines
o Precision positioning - satellite geodesy
o Geoid determination - physical geodesy
o Geodynamics - integrated geodesy
 Geodetic surveying: Curves surface of Earth considered by doing calcs on an ellipsoid
 Plane surveying: surface of ellipsoid approximated by a plane
 Geodetic surveys: relative positions of widely spaced monuments
 Control surveys: Establish horizontal and vertical positions

, o Horizontal: determine geodetic latitude, geodetic longitudes
o Vertical: Determine elevations (benchmarks) for a network of reference monuments
o Cutting plane of a meridian: Passes through point P and north/south poles
 Longitude:




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REPRESENTATION OF DISTANCES AND ANGLES ON EARTHS SURFACE
 Latitude vs longitude:
o
COORDINATE S




SYSTEMS AND DATUMS
 Coordinate Systems:
o Cartesian