SonarMite BTx/SPx v5.02 © 2016 Lymtech
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Data Collection Techniques
When not used as a „Dumb‟ echo sounder in conjunction with a data logging package
the SonarMite can be used in conjunction with the following data types to create full
XYZ hydrographic data using the SonarW7 software package….
Total Station XYZ data plus Time
XYZ data from RTKGPS plus Time
XY data from DGPS plus Tide plus Time
Range and Bearing from hand held laser plus Tide plus Time
Simple event marking past known position markers
The basis on which all data correlation is achieved is internal time base, so
particularly when using the SonarMite with GPS data the clocks should be
synchronised to GPS time (UTC).
Sound Velocity Settings
The SonarMite default Speed of Sound in Water(SoS) setting is 1500m/second,
facilities to vary this have been provided in the calibration or in post processing. In
practice this velocity value can vary due to several factors …
Water Temperature
Water Salinity
Water Turbidity
All of the above factors vary the density of the water in some way and effect the „time
of flight‟ of a pulse of ultrasound in water and hence the depth calculated from this
time by the SonarMite. The user can either measure the speed of sound in water by
taking velocity profiles using a dedicated velocity measuring device or can use the
SonarMite static over a known depth to a flat, firm base and then compare the
measured value with the known depth. The difference in Sound Velocity between
warm fresh water and cold salt water is about +/-30m/Second which represents a
change of depth of +/-2%, this must be viewed in context with typical depths of the
survey, if a typical depth is 10m then the error could be about 20cm.
The Sound
Velocity setting is the largest source of measurement error when care is not
taken in setting it correctly.
Internal Battery Charging
The SonarMite BTX is fitted with an internal sealed Nickel Metal Hydride battery
which provides 2.8Ahr @ 10vDC and a mains powered battery charger capable of
bulk and float charging to give the most efficient battery cycle. The user should avoid
running the SonarMite until the batteries are completely flat as there will be a high
risk of both data loss and permanent damage to the batteries. The charger will
illuminate FLASHING GREEN when bulk charging and CONSTANT GREEN when
charged, the charger illustrated may change if a local mains variant is required.
