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7.
GPS OPERATION
When the SAMBAT is started using WINMEMO II, it looks for its reference position, i.e. the position to be
considered as its anchor position. This position will be sought by the probe after a delay corresponding to the
GPS measurement rate.
Start via
WINMEMOII
GPS Measurement
Once the reference position is recorded, the probe will take its GPS position at the GPS measurement rate set
by the user, and record it in a "GPS position" file.
If the GPS alarm function is active, the SAMBAT analyses each GPS position and checks if the probe drift
exceeds the turning circle defined by the user.
If the probe detects a drift, an alarm file is created and sent by GPRS.
GPS accuracy does not allow for infinite resolution. Therefore, this parameter is limited to a radius of minimum
100 meters in order to prevent inadvertent alarms. Above 100m, the setting resolution is the meter.
For example, for a turning circle of 115m, any position of the SAMBAT buoy fitted with a GPS greater than
115m will generate an alarm.
7.1
MANAGEMENT OF ALARMS AND CONSIDERATION OF TIDAL RANGE
When the probe detects a GPS position greater than the turning circle, the GPS position recording rate changes
and switches to 1 hour. The probe records its GPS position every hour as long as it remains above the turning
circle (Dmax in the diagram below). After three consecutive positions greater than the turning circle, the
SAMBAT generates an alarm.
When the probe is lying down or in a situation where it cannot find a GPS position, a Timeout position will be
recorded. In this case, the GPS position cycle will change and the next position will be recorded in 4 hours. If
GPS position recording was not possible due to the tidal range (buoy flat), this enables full tide conditions to be
resumed.
If the probe detects 3 consecutive timeouts, a GPS alarm is generated.
7.2
GPS INSTALLATION PRECAUTIONS
The GPS is integrated in the GPRS aerial.
However, to enable the GPS to operate, the aerial must be above water. Position recording with the GPS
aerial underwater would cause a GPS Timeout.
nke
Tel 02-97-36-41-31
Reference position
GPS Measurement
rate
GPS<Dmax
GPS<Dmax
GPS
measurement rate
Fax 02-97-36-55-17
GPS position
GPS Measurement
rate
GPS>Dmax
N°1
GPS measurement
rate
http://www.nke.fr
GPS position
rate
GPS>Dmax
GPS>Dmax
N°2
N°3
1h
Alarm
PAGE 23/43
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