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11. GPS accuracy and time to Fix and SMS Delays
11.1 Accuracy
Place the tracker in a position to allow the best possible open sky view. Obstruction can
affect the time and accuracy of the GPS data. The accuracy of the GPS position
depends on a number of factors. First of all, the number of satellites from which signals
can be received by the tracker. More satellites will give a better accuracy. The number
of the satellites received is an important factor.
1- Better Accuracy
2 - Less accurate
Further more, a clear sky view will give better results than a sky view which is
obstructed by buildings and/or trees. Accuracy according reception of signals as shown
in picture 1 can sometimes be within a few meters.
11.2 Time to Fix, Time of acquisition of GPS data
Apart from the points listed under 11.1, the time of a 2D or 3D fix depends on the
received signal strength of the satellites. It is therefore important not to put obstacles
between the tracker and the open sky. For example, a thick jacket over the tracker will
influence the sensitivity and will result in longer times to acquire the satellite data. In
normal operation condition the time for 3D Fix is around 40 seconds(Cold start) and
between 6-20 sec. in a “warm” start condition.
11.3 Time delays due to GSM Network congestion
Depending on the GSM network traffic, SMS instructions and/or data transfer can be
very quick. However, due to heavy traffic congestion these messages can sometimes
be delayed. It is recommended if this kind of delay happens to wait for awhile before
resending a SMS message.
It is strongly recommended to use SIM cards in your mobile phone and tracker from the
same telephone company to avoid latency in the SMS handling. Messages between
different network providers are handled differently and can sometimes cause excessive
delays. When very long latencies occur please contact the supplier for special settings
to minimize this problem
