The Depth Filters / Draft button opens a window that allows the user to review the measured depths from each beam and the final processed cross section . The user can also change the primary depth reference and indicate whether or not to use composite depths. QRev defaults to using inverse depth weighting to compute the mean depth when the 4 slant beams are used. The user can also change the filter type to try and eliminate unreasonable and erroneous spikes in the data.
Summary Table
The summary table allows the user to select which transect is displayed in the graphs (by clicking on the desired row), provides information on beams with invalid depths, and allows the user to change the draft.
Filename—Filename of the transect.
Draft—Distance from the water surface to the transducers.
# Ensembles—Number of ensembles in the transect.
# Invalid Beam 1—Number of ensembles where the depth in beam 1 is invalid.
# Invalid Beam 2—Number of ensembles where the depth in beam 2 is invalid.
# Invalid Beam 3—Number of ensembles where the depth in beam 3 is invalid.
# Invalid Beam 4—Number of ensembles where the depth in beam 4 is invalid.
# Invalid Vert Beam—Number of ensembles where the depth in the vertical beam is invalid.
# Invalid External—Number of ensembles where the depth from the external depth sensor is invalid.
Discharge Prev. —Total discharge prior to most recent filter change.
Discharge Now—Total discharge after applying the most recent filter change. If no filters have been changed, the discharge now will equal the discharge previous.
Discharge % Change—The percent difference between the discharge previous and the discharge now due to the last filter change.
The Individual Beams cross section graph displays the cross section as measured by each individual beam. All available beams or depth sources are active in the graphs. The user can check or uncheck the check box associated with each beam to display or hide that beam; this action does not affect the computations. The circles at the top of the graph identify ensembles that have no depth. Circles on the lines of the individual beams indicate a depth that has been determined to be invalid based on the selected filters. The color of the line or circle corresponds to the beam or depth source.
The Processed Cross Section displays the final cross section. The final cross section is based on the selected depth reference and the results of the filters and interpolation. The check boxes to the right can be used to compare the final cross section to other alternatives.
The Depth Reference is a popup menu that allows the user to select from all available depth sources.
4 Beam Avg—The ensemble depth is computed as the average of the 4 slant beams.
Comp 4 Beam Preferred—The ensemble depth is computed as the average of the 4 slant beams, but if that results in an invalid depth, other available valid depth sources will be substituted according to the priority defined in the table below.
Vertical—The depth from the vertical beam is used as the ensemble depth.
Comp Vertical Preferred—The ensemble depth is the vertical beam depth, but if the vertical beam depth is invalid, other available valid depth sources will be substituted according to the priority defined in the table below.
Depth Sounder—The depth from an external depth sounder is used as the ensemble depth.
Comp DS Preferred—The ensemble depth is the external depth sounder depth, but if the depth from the external depth sounder is invalid, other available valid depth sources will be substituted according to the priority defined in the table below
BT Beam Averaging determines if the average depth from the 4 slant beams is computed using a simple average or an inverse depth-weighted method (IDW). The inverse depth-weighted method is preferred and the QRev default. However, to allow duplication of RSL computations, the simple average option is available.
The two options available to filter out spikes in the depths are the method used in WR2 and a method based on a LOWESS smooth. The method used in WR2 will tend to filter out the lowest (deepest) data because the method was designed to filter out multiple reflections. The LOWESS smooth filter only works well with continuous data. Gaps in the data can cause the LOWESS smooth filter to miss what appear to be obvious spikes. The filter can also be turned off.