Detailed study of modern surveying instruments such as total stations, GPS, GNSS, and laser scanners. Instruction on methods for collecting, processing, and analyzing spatial data.
LECTURE 3 (CH13-15)
GPS AND RECEIVERS
GPS: Global positioning system
GNSS: Global navigation satellite systems is entire satellite system
Broken into 3 parts
o Space segment:
Consists of 24 satellites operating in 6 orbit planes spaced at 60 degree
intervals around equator
Orbital planes inclined to equator at 55 degree
4 additional satellites held as spares
o Control segment
Monitoring stations: monitor signals and track positions of satellites over time
4 of these stations
Colorado Springs, Ascension, Diego Garcia, and Kwajalein
Information relayed to master control station in Air force base
o User segment
Consists of 2 categories of receivers
Standard Positioning Service (SPS)
Precise Positioning Service (PPS)
Calculating Frequency
GPS MEASUREMENTS
Reference Coordinate Systems:
o To determine the positions of points on Earth from satellite observations, 3 reference
coordinate systems needed
, i. Space related satellite reference coordinate systems: positions at the instant they are
observed
1. 3 Dimensional rectangular systems defined by satellite system
ii. The 3 dimensional rectangular coordinates then transformed into 3-dimensional
rectangular geocentric coordinate system (physically related to Earth's measurements)
iii. Then geocentric coordinates transformed into geodetic coordinate systems
o First set of coordinates:
Satellite reference coordinates: Xs, Ys, Zs
Reference axis Xs
Origin of Xs, Ys, and Zs coordinate systems is at G
Ys axis is the mean orbital plane
Zs axis is perpendicular to Xs-Ys plane
Satellite at position S1: Coordinates of Xs1, Ys1, Zs1
o Second set of coordinates:
Gives a frame of reference relative to Earth
Geocentric coordinate system
Coordinates Xe, Ye, Ze
Superimposed on an ellipsoid
X axis passes through prime meridian
Origin center at mass center of Earth
Converting from Satellite coordinates to geocentric coordinates:
Requires 4 angular parameters
Inclination angle , 'i': angle between orbital plane and Earth's equator
plane
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