Chesapeake Times, vol 8 | January 2022
New in SonarWiz 7.09, we are introducing binary support for Kongsberg NavLab BIN files to SonarWiz. Kongsberg uses NavLab post-processing software to calculate optimal position estimates for the HUGIN family of Autonomous Underwater Vehicles (AUV).
NavLab computes the orientation and velocity of the AUV, based on available sensors, such as GPS/acoustic positioning, doppler velocity and inertial measurement records. Navigation processed with NavLab is always more accurate than a real time navigation system with comparable sensors.
Because NavLab processing occurs after the mission is completed, raw sonar data collected during the mission needs to be adjusted with the refined trajectories before the data is finalized. In SonarWiz, this navigation adjustment can happen at two different stages of processing:
- Before the data is loaded into SonarWiz. The utility program NavInjectorPro can directly update navigation in XTF, SEG-Y, JSF, and SDF files. Updating the navigation in this way is vendor-neutral and useful for long term data archiving. You can be sure that the binary files and the SonarWiz project are using exactly the same navigation source.
- After the data is imported into SonarWiz. If the raw data has approximate navigation, the data can be loaded into SonarWiz and then updated at a later point. This workflow allows processors to start target identification before the navigation has been finalized.
NavInjectorPro (NIP) is a stand-alone utility program distributed with SonarWiz whose purpose is to batch-inject or batch-replace time series data in sonar files. The most common fields to replace are latitude and longitude, but NIP can be used to inject or replace any time-based variable in the file, including depth, altitude, heading, orientation, KP, event numbers and more.
NIP can directly read and write XTF, SEG-Y, JSF, and SDF formats. NIP can also modify any sidescan, sub-bottom or bathymetric file that can be loaded into SonarWiz, providing indirect support for more than 40 different sonar formats.
In addition to the new support for NavLab binary files, NIP supports Applanix SBET and provides a robust template system for importing almost any navigation file that can be formatted in tabular format.
A HUGIN example with a file type supported by NavInjectorPro
The HUGIN AUV data we have for example, was outfitted with a HISAS synthetic aperture sonar for imagery and an EM2040 for bathymetry. The HISAS data was provided in XTF format which NIP can modify directly.
To replace the navigation in the HISAS XTF files:
- Open NavInjectorPro and select XTF in the Process Files of Type… section.
- Select the Kongsberg NavLab bin Files from the Navigation File Template drop down.
- Then specify the source directory with the XTF files to modify, and the destination directory for where you want the modified XTF files to go (your original files are not modified)
- Browse for the NavLab BIN file with the update navigation file.
- Click the Start… button. SonarWiz will present you with options to set how the new navigation will be interpolated onto the original pings. The default options are usually good, but you have control over the details
- Make any necessary adjustments and click OK
NavInjectorPro will batch process all of the HISAS files in the source directory and create new XTF files with the updated navigation in the destination folder. If the sonar files and the replacement navigation file do not overlap, those files will be handled according to your selections. A comprehensive log is created to review the operation.
If you load both the original and the adjusted XTF files into SonarWiz, you can see the shift in the imagery between the two files.
A HUGIN example adjusted after loading the data into SonarWiz
HUGIN EM2040 bathymetry data is stored in ALL format. The ALL format is not directly supported by NavInjectorPro and so these data need to be adjusted after the bathymetry files have been loaded into SonarWiz. Once the data is imported into the SonarWiz Project, NIP has an option to adjust SonarWiz Bathymetry in place. This workflow is very similar to the first example described above.
Another option, for bathymetry data, is to load the NavLab files into SonarWiz as an External Navigation file and then apply the updated navigation during the merge process.
To load NavLab files as an external navigation file:
- Import the ALL files into a SonarWiz Bathymetry project
- In the Project Explorer, Right-Click External Navigation branch and select Add/Import External Navigation Files…
- In the File Open dialog that opens, select the Kongsberg NavLab template in the File Template drop-down and load the bin file.
- When you merge the bathymetry, change the Position Source and Attitude Source from Internal to External
Your bathymetry files will be processed using the Navlab navigation and attitude rather than the original unprocessed navigation stored in the ALL files. You can easily switch back to the original navigation by re-merging the data using the Internal options.
The ability to adjust navigation after sonar data has been collected is useful for AUV operations which will normally require re-processing of the raw navigation after the mission is completed. For file formats with direct support in NavInjectorPro, such as the HISAS XTF formatted files, NIP can directly create updated binary files in native format. For formats that NIP does not directly support, but that can be imported into SonarWiz – such as the ALL format used by the EM2040 – you can import the files first and then modify the navigation in-situ in the SonarWiz project.
– David Finlayson, Chief Scientist