Lecture 6 - Geodetic Positioning Techniques Flashcards
What are different geodetic positioning techniques?
Astronomical positioning
Satellite positioning
Vertical positioning
Kinematic positioning
What are measurements with different geodetic positioning techniques?
Astronomic latitude, longitude and azimuth, direction measurements to stars
Gravity and gravity gradient measurements
Earth tide measurements
Geodetic measurements: angles (horizontal and zenith), distances, height differences
What is triangulation?
A method to get positions of the angular vertices of series of triangles by measuring the internal angles or directions using theodolites with the limited number of baselines. (3D)
Measurement corrections: Due to the instrument and target offsets; due to the reduction of direction from natural surface to the ellipsoid (surface); due to arc-to-chord reduction the correction from the curve to the chord on grid plane (because the projected direction from the ellipsoid onto the grid plane is not a straight line)
What is trilateration?
A series of triangles with all the sides (or sections) measured by EDM instruments (2D)
Corrections: Due to the instrument and target offsets; due to atmospheric refraction; due to the instrument constant (zero error) and scale factor error; due to the reduction from the natural ground to the reference ellipsoid; due to the projection from the reference ellipsoid to the mapping grid plane
Are triangulation and trilateration used today? If not, what has replaced it?
Triangulation has become obsolete and replaced by 3D GNSS.
Replaced by triangulateration: combining of triangulation and trilateration to produce a control system in which all the angles and sides are measured.
What is traverse?
A series of straight lines connecting successive survey stations whose positions are to be determined based on the previously surveyed points for observing the next point.
