Simrad FM90, Reference Manual

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Ping to Ping filter
Clicking this button will enable or disable the Ping to Ping filter. This filter reduces noise
and shows a more persistent net profile.
This filter averages the image from ping to ping so that slow-moving features
(such as a school of fish or the net) will persist, while reducing noise in the image.
The Ping to Ping filter is especially useful when the image is constructed from
multiple pings, such as when the
Bottom or Bottom - Hard sonar application is selected.
Note
You can adjust the strength of this filter in the
Display Widget
. A high filter strength will
remove more speckle noise, but may blur the edges of images.
Disable this filter when there is fast movement in the sonar view, such as at the start or end
of trawl-net deployment.
Related topics
Applying filters, page 52
Noise Reduction filter
Clicking this button will enable or disable the Noise Reduction filter. This filter reduces
noise by boosting weak echoes and suppressing strong echoes.
The Noise Reduction filter automatically scales incoming echo data to maintain
a proper dynamic range. This filter works best when the bottom appears in the
trawl image.
For maximum effect, the Noise Reduction filter can be used at the same time as the Ping
to Ping filter. However, you may wish to disable the Noise Reduction filter if you see too
much background noise.
Related topics
Applying filters, page 52
Limit Strong Targets filter
Clicking this button will enable or disable the Limit Strong Targets filter. This filter reduces
noise by suppressing strong echoes, but does not change weak echoes.
This filter suppresses strong echoes by limiting the echo level with an
automatically calculated threshold. The Limit Strong Targets filter works best
when many strong point-like targets appear, such as a footrope.
Functions and dialog boxes