GPS
GPS is the shortened form of NAVSTAR
GPS. This is an acronym for NAVigation
System with Time And Ranging Global
Positioning System.
GPS stands for:
Segments of GPS
The GPS consists of three segments. Namely,
SPACE SEGMENT
CONSTELLATION
The Control Segment consists of one master control station, 5 monitor stations and 4 ground antennas distributed amongst 5 locations roughly on the earth’s equator. The Control Segment tracks the GPS satellites, updates their orbiting position and calibrates and sychronises their clocks. A further important function is to determine the orbit of each satellite and predict it’s path for the following 24 hours. This information is uploaded to each satellite and subsequently broadcast from it. This enables the GPS receiver to know where each satellite can be expected to be found. The satellite signals are read at Ascension, Diego Garcia and Kwajalein. The measurements are then sent to the Master Control Station in Colorado Springs where they are processed to determine any errors in each satellite. The information is then sent back to the four monitor stations equipped with ground antennas and uploaded to the satellites.
CONTROL SEGMENT
GPS COORDINATES SYSTEM
PROBLEMS IN HEIGHT
Geoid separation
The distance from the surface of the reference ellipsoid to the geoid measured outward along the normal to the ellipsoid.
Standard Positioning Service
Precise Positioning Service
Surveying with GPS
Measuring TECHNIQUE
STATIC SURVEYS:
RAPID STATIC SURVEYS
KINEMATIC SURVEYS:
RTK SURVEYS:
Differential positioning
Determination of relative coordinates between two or more receivers which are simultaneously tracking the same GPS signals.
DGPS
Differential GPS. The term commonly used for a GPS system that utilizes differential code corrections to achieve an enhanced positioning accuracy of around 0.5 - 5m
Stop & Go Survey
The term Stop & Go survey is used in connection with GPS for a special kind of kinematic survey. After initialization (determination of ambiguities) on the first site, the roving receiver has to be moved between the other sites without loosing lock to the satellite signal. Only a few epochs are then necessary on these sites to get a solution with survey accuracy. Once loss of lock occurred, a new initialization has to be done.
MAP PROJECTION AND PLANE COORDINATES
TRANSVERSE MERCATOR PROJECTION
LAMBERT PROJECTION:
DIFFERENT GNSS SYSTEM
THANK YOU.
K KONWAR, ADS
ASSAM SURVEYS