1007D Altimeter Operators Manual 974-72007001/1.0
Tips for Successful Altimetry Page 37
Kongsberg Mesotech Ltd.
Port Coquitlam, BC - Canada
Cause
Possible Solution
The acoustic returns from the
sea-bottom or target are too
narrow or weak.
Decrease the minimum threshold and/or the
minimum return width and/or increase the TVG
gain offset. For long ranges a longer transmit
pulse length may be required. Target strength
will depend on its shape, size, composition, &
texture, as well as its location & orientation
with respect to the altimeter's beam. If
necessary, re-orient the altimeter to minimize
the acoustic grazing angle to the target/bottom.
Acoustic noise or spurious
additional targets are being
detected outside the range
window.
This may be seen as erratic altitude
measurements due to noise, mid-water targets,
or multipath interference. These can be filtered
out by judicious adjustment of the minimum,
maximum range, increasing the minimum
threshold, and decreasing the TVG gain offset.
Select the "peak return" decision method for
bottom tracking applications.
If necessary, re-orient or relocate the altimeter
away from nearby objects.
Large discontinuities in the
bottom.
Increase the range window to accommodate
anticipated gradients.
Multipath interference
Reduce the altimeter ping rate to reduce the
effect of multipath. Select the "first return"
decision method for bottom tracking
applications.
No echoes received due to air-
bubbles on transducer face.
Keep transducer face clean and free of air
bubbles. If necessary, use a mild detergent.
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