The rollout of the new BioBase EcoSound vegetation and bottom hardness algorithm required substantial refactoring of our core processing code. Read about the changes here. While we were under the hood, we took the opportunity to implement some enhancements that our frequent BioBase users should appreciate. NOTE: Users still select the unit (Imperial or Metric) in the primary user profile area of their BioBase account (My Account).
Set default processing preferences
Users can now set preferences for how they would like their sonar log processed (e.g., depth offsets, sonar channel for vegetation mapping, buffer extent, etc). The defaults are robust and optimized based on previous user experience. Novice users should not have to adjust these settings in order to get a good map output. However, survey conditions and approach are highly variable and settings may need to be adjusted by the user to get the best possible map output
Sonar channel for vegetation
As described in an earlier post [cite blog link when published], users can select the option to process either the downscan (455 or 800 kHz) channel or primary (200 kHz) for vegetation (the previous EcoSound only processed 200 kHz Primary). Both channels have performed well in preliminary tests but the outcomes appear highly dependent on local conditions (depth, water clarity, vegetation type and density). We recommend users run their own tests to determine which one performs best for the environments in which they are working.
Overlay vegetation canopy and depth point delineations on Sonar Imagery
Users can select a preference that will overlay points where depth (red in Downscan and blue in Primary) and vegetation canopy height (Green) is declared. These are images of points that are overlayed onto the sonar imagery, so there may be slight imprecisions in some cases. If a vegetation point is at the surface, then that means vegetation grew to the surface or the signal in that area was very noisy. This setting is off by default.
Buffer and Grid Cell
Select a buffer that controls how much of the map output is interpolated or extrapolated. Select the grid cell (minimum mapping unit) that defines the minimum resolution of any particular point on the map. If you are mapping small ponds with dense transect spacing, 1m grid cells are appropriate. Mapping large lakes with wide transects, consider larger grid cells and buffers. NOTE: Buffer settings are always in metric. Prior to deviating from the default 25-m buffer and 5-m grid cells, we recommend users consult this blog or other hydrographic mapping resources about best mapping/interpolation practices.
Insert an offset that will be added (positive number) or subtracted (negative number) from individual depth measurements for every uploaded trip automatically. Vegetation height will be lowered if the new depth is shallower than the vegetation but vegetation height (e.g., negative depth offset) will not be lengthened if a positive offset is put in place. This setting will be used most often for users who have a transducer that is a fixed depth below the surface.
Vegetation Biovolume Detection Threshold
This setting controls the minimum length of a plant (expressed in biovolume as a decimal) that could be detected by EcoSound algorithms. Note that in deeper waters 1% represents taller plants than shallow waters. This setting is an important control against bottom debris erroneously being detected as vegetation. Often the algorithms do not know what is debris and what is vegetation. Now, users can control this setting. EcoSound processing will set the final vegetation coordinate value to zero for points where vegetation is preliminarily determined to be less than this amount. NOTE: interpolation can generate smaller values than the minimum detection threshold because it makes predictions on a neighborhood of values (e.g., 5% bv surrounded by 0% bv will result in values less than 5% for a grid cell even if the user setting is 0.05).
Minimum and Maximum Depth For Vegetation
As the depth gets shallow (e.g., less than 1 m), the target separation between the transducer and the bottom becomes quite narrow and difficult for the algorithms to confidently separate noise from bottom and plant characteristics in these high energy environments. Users can set the depth at which any vegetation or bottom hardness points shallower will automatically be discarded. In contrast, in deep areas, sometimes thermoclines or insect emergence can be mistaken for deep growing vegetation. As such, users can now set a maximum depth of plant detection whereby any points that are interpreted as vegetation deeper than this threshold will be converted to biovolume values equal to zero.
Apply global settings or customize settings on an individual basis
Users also have the ability to apply these global settings or customize their settings on an individual basis for a specific trip or merge of interest.
NOTE: Reprocessing of the raw sonar log is required if a different sonar channel selected. After 90 days of the upload date, sonar logs are archived and the ability to reprocess with a different sonar channel is no longer available to the end user. Contact BioBase support if you have special reprocessing requests