28
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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 Equ ivalent
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
In C/A code, horizontal error combined with all errors is 28m when SA does not activate and 100m when SA
activates.
SA code means enlargement of error range so that Deviceed States may limit use by non -allowed GPS satellite users
during military operation.
Basically, GPS is not much affected by weather. It cannot be said that there is no effect at all, but there is no a bsolute
effect. Depending on situation, as sunspot activity of sun becomes active, if magnetic field change around earth becomes
severe, GPS reception cannot be well performed.
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Cautions during Use of GPS
①
Do not dissemble, repair, or remodel it randomly.
②
Pay attention not to pour water or liquid.
③
Avoid use in environments with shock, high temperature, high humidity, etc.
④
Use it by avoiding the following conditions.
⚫⚫
Tree foliage.
⚫⚫
Next to tall buildings, beneath bridge, beneath elevated road.
⚫⚫
Inside buildings, tunnels, aircraft, ships etc.
⚫⚫
Beneath other objects blinding GPS antenna parts, etc.
⚫⚫
When covered by the palm of a hand.
⚫⚫
Do not put gold, metallic objects, or electric wave emitting objects around GPS. Do not leave GPS
for long time where there is severely high or low temperature.
5 Support Guide
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Self Check List before contacting technical support
The following checklist will be helpful in solving problems encountered while using your navigation system. Before
reviewing the following checklist, check the equipment connection and operation procedure.
