Blog from July, 2014

Fledermaus 7.4.1 (released 4 July 2014) included new tools for working with watercolumn data – semi-automated feature detection and cluster analysis.  These research tools were originally written by Dr. Tom Weber of the Center for Coastal and Ocean Mapping (CCOM) at the University of New Hampshire to help detect seafloor seeps in watercolumn data.  The QPS developers have used the Fledermaus plugin architecture to create a new tool that is now available to all FMMidwater users, another example of successful partnership between researchers and industry. 

We will be hosting webinars on July 22nd and July 23rd to demonstrate the new functionality, please visit the webinar event page for more information and to register.  We have also created two new Howtos with step-by-step instructions, the first explaining how to use the Feature Detection tool in FMMidwater and the second describing the associated Point Clusters SD object and clustering analysis tools found in Fledermaus.


Preliminary view of a watercolumn file prior to any filtering.



Scanning for potential seeps manually using signal level.



Potential seeps detected using despeckling filter in the Feature Detection tool.

 


To view a larger version of any image, simply click on it.

 


Line Data Manager Functionality

The majority of the Line Data Manager functionality has been integrated into the Processing Manager. Future QINSy versions will likely include the as yet not ported functions. For the time being the Line Data Manager may be used to perform these functions. In preparation for new functionality the Processing Manager stores the survey line data in two file formats. The first file format is the PRO-file format which is also used in the Line Data Manager and the second format is the QGF-file format. In future releases the QGF-file format will be used throughout QINSy.


Line Data Manager showing PRO-file

The Line Data Manager functionality may be found in a separate ribbon which becomes available after selecting a Line file in the Project Explorer pane. A Line file may either be newly created by selecting the New Line from the File menu or by importing from a AutoCAD DXF, DWG or Microstation DGN file. An option is also included to export the data to AutoCAD DXF file format where by the following AutoCAD versions are supported: R13, R14, 2000, 2004, 2007, & 2010.


Improved workflow to generate grid from QPDs

Only two steps need to be executed in order to fill a grid using a number of QPDs:

1.Select QPDs which are to be added to the grid file
2.Select/Create the grid file and additional properties.


Selecting QPDs to add to grid file



Selecting grid file and additional properties

 

Improved workflow to edit data using Qloud

It is no longer necessary to separately group the QPDs. The user may just select the QPD files and choose the edit in Qloud option.


Selecting QPDs to be edited in Qloud

 

Once the correct files have been selected the QTM file settings may entered. This dialog gives the user control over which systems will be part of the QTM file and what information will be transferred into the quality field of the QTM file. In case a Navigation Surface was created the program will re-use as many settings as possible.


QTM settings dialog

 

Once the QTM file creation is finished Qloud will open to allow processing. While processing in Qloud the QPD files will remain marked as locked in the Processing Manager.


QPDs being edited in Qloud shown as locked

 

When the processing is finished and Qloud is closed the user is given the option to immediately synchronize the changes made to the QTM file back to the QPD files.

Synchronize changes in QPD dialog 

 

The user may however decide not to synchronize the changes in the QTM file to the QPD files. This will allow the user to come back at a later stage and resume editing in Qloud i.e., the next day.

While the changes in the QTM file have not been synchronized back to the QPD files the QPD files remain marked as modified.


QPDs shown as being modified 

 

Once the user is finished processing the data in Qloud the changes may be synchronized back to the QPD files by using the Synchronize option.


 

 

When: Version 7.4.1 of the Fledermaus Suite, released 4 July 2014 includes an important bug fix that may impact the appearance of your processed backscatter.  

What are the changes?

It was recently discovered that the backscatter corrections being done in FM Geocoder Toolbox (FMGT) were not correcting for seafloor 3D incidence angle, even when corrected bathymetry was included in the processing routine.  We have added a fix to use a Reference Grid (in Fledermaus SD format) to determine the topographic slope during processing and mosaic creation.  To clear up any potential confusion, it is important to point out that the corrected bathymetry data that has been necessary to import data into FMGT have only ever been used for georeferencing seafloor imagery.  The original Geocoder software from UNH provided the ability to compute the 3D incidence angle with a Reference Grid, however, this was only implemented for sidescan sonar imagery and not for multibeam imagery.  We have followed the same strategy for multibeam imagery now and the Reference Grid is now used to estimate each beam's 3D incidence angle with the seafloor.  This more accurate method of calculating the incidence angle directly improves the accuracy of the ensonified area correction, which is a function of the projected beam footprint size on the seafloor.

While implementing the Reference Grid calculations for multibeam imagery, a small number of errors were noted in the original UNH Geocoder approach.  These were corrected for the multibeam imagery correction algorithms, however, the corrections have not been ported to the sidescan signal level corrections yet.

Who does this impact?

This type of correction is particularly important for ARA users since the input signal to ARA now represents the seafloor's true backscatter value with much higher fidelity than before.  For FMGT users who focus primarily on creating seafloor mosaics only, the new algorithm will dampen topographic effects, such as higher signal levels on inward facing slopes and lower signal levels on outward facing slopes.  As part of our ongoing efforts to improve the underlying Geocoder algorithms from UNH, we have identified the need to propagate the angle and terrain corrections into the AVG stage of processing.  Once this is complete, mosaic imagery will have a much higher fidelity in representing seafloor backscatter.  Look forward to this in a future release.

The terrain correction can be applied for Kongsberg, Reson and R2Sonic multibeam systems that have the sonar beamwidth and pulse length parameters correctly recorded in their data stream.  The corrections are done for both .ALL input format (Kongsberg only) and for .GSF (Reson, R2Sonic and Kongsberg).

Where to get more help?

This HowTo explains how to add a Reference Grid and create a new mosaic.  If you have any questions or need further clarification, please contact Support (support@qps.nl).