MyDean VR3 - GPS Error Sources

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GPS satellite C, Distance C, and positioning point
Intersection point of 3 sections, Principle of GPS positioning
GPS is accompanied with about 5m~15m error even though SA does not activate during
single positioning (absolute positioning, 1 point positioning) where position is measured
by only one receiver, so the single positioning method is being utilized mainly for
navigation such as vehicle, ship, aircraft, etc. or in GIS field where allowable error is
relatively big rather than for measurement.
 Cause of Error Occurrence in GPS
Factors dropping accuracy in position measurement of GPS can be largely classified into
3 parts.
First, errors occurring due to structure factors include satellite time error, satellite position
error, refraction in ionosphere and troposphere, noise, multi-path, etc.; secondly, there is
geometrical error due to arrangement situation of satellite; and lastly, there is SA (Selective
Availability) that is the biggest error factor.
Potential combination of all these factors brings about very big error result, which is called
UERE (User Equivalent Range Error). Each error varies greatly depending on time and
place.
 Satellite time error 0-1.5 m
 Satellite position error 1- 5 m
 Refraction in ionosphere 0-30 m
 Refraction in troposphere 0-30 m
 Receiver noise 0-10 m
 Multi-path 0-1 m
 SA(Selective Availability) 0-70 m
GPS Satellite C
GPS Satellite A
Measuring point
(Intersection point of 3 sections)
[How to measure position via GPS]
Distance A
Distance B
Distance C
GPS Satellite B