Chesapeake Times
Technical Review, Issue 1
Q1 2020

Letter from the General Manager

Welcome to the first edition of the Chesapeake Times – a quarterly review from our team to let you know what we are working on here at Chesapeake. We go beyond the User Guide step by step and try to offer you some deeper insight into the program. Many of these features are requests from you – our clients - as we continue to build our program to add better tools for data analysis, new sonar interfaces, or simply make it easier to use.

First though, I want to take a step back and to make sure everyone is managing ok, as we continue to work through the corona virus outbreak. Here at Chesapeake, we are all doing well, following the guidelines to keep us safe. Most of us had on our calendar the Oceanology International (OI) conference in March – the traditional kick off to the survey season, and a time that we use to meet up with colleagues and see the latest innovation from manufacturers. 

In the absence of OI, we have seen some creative ways to keep the community informed – webinars, newsletters, emails and phone calls, as we push through to do our best during these uncertain times. At some point – hopefully soon, we get back to our familiar routine. Back on the airplane, on a boat for a demo, meeting up with clients and running a training class in front (without using a video link)

In the meantime, we are home together, which isn’t a bad thing. For me, travelling is part of my job. I’m now home (all the time) and we find our time is filled with activities and games. Last week, I sat down with the kids to do a 700-piece puzzle. We did our best, as we got 699 pieces together. One piece was missing – really. And it was right in the middle of the puzzle. 

Our next release, SonarWiz 7.6 is scheduled to get out early May. It’ll be posted on our website for folks to download. We are putting some final pieces together now, and then will do a complete stress test for the program, to make sure those pesky bugs are found. We also updated the User Guide and added a few Quick Start Guides to get you up and running. Overall, the new release has a nice selection of new features and updates to our program. 

In this newsletter, you will read about some of these changes to the software. And then the cycle begins again – as we build onto this release with new features, updates and some new graphical displays to make sonar interpretation is easier. With your input, the program will continue to get better for all. Thank you.

- Harold Orlinsky, General Manager
SonarWiz 7.6 New Features and Technical Notes

Beam Performance Test..................... Harold Orlinsky, General Manager
Processing Multibeam Imagery........... David Finlayson Chief Scientist
A-B Change Detection........................ Harold Orlinsky , Howard Unkeles
Forward Looking Sonar....................... Christopher Favreau, Program Manager
Improved 2D & 3D Drawing .................. Jonathan Fleetwood, Senior Developer
Webinar April 21, Marketing................ Ashley Chan, Office Manager
Customers in the News .......................... Stephen D'Andrea, Business Manager
Co-founder Corner ................................... John and Eileen Gann, co-founders
Beam Performance Test – new feature in SonarWiz 7.6

If you’ve ever been asked - how good is your multibeam system, don’t fall into the trap of just looking at the system specification for the sonar. It’s not the answer you need. You need to consider everything that goes into the system to come up with an answer. One method is the Beam Performance Test, a new module in SonarWiz. The program provides the user with information about each beam and measures differences along the swath, providing a snapshot of how the overall system is expected to perform during your survey operations.

A sonar that is promoted at a 150-degree system – 7.4x water depth, will provide you a depth measurement across the seabed. Your job is to determine how good all that data is. How far off nadir will the depth be accurate enough to use? Can you make improvements to the system to increase the usable swath? 

Using the performance test is straightforward. We create a reference surface with the system and use an independent check line to compare each beam to a known depth. The output is viewed in a graphical display, to provide you the expected error across the sonar swath:
One critical part of the process is to create a proper reference surface. Find a flat area (slope less than 3%) and collect sonar data in the along track and across track direction, oversampling the bottom. In processing reduce the swath to 45 degrees (the inner section of the swath is more accurate). The area doesn’t need to be large, but needs to ensure the reference line falls inside the area.
Survey lines for reference area, line spacing 20m
Check line run orthogonal to the survey area, ensuring all biases are removed.
The output of the Beam Performance Test in SonarWiz provides the user with useful information for the system, including IHO pass/fail criteria, data histograms, reject ratio and information for each beam (the latter would be useful if a single beam has a failure).

Taken together, this information should be used for planning your next survey. If there is an IHO Special Order requirement, and the system fails after 52 degrees (104 degree swath), line planning should use that criteria. The nice thing about the Beam Performance Test is that the results are good for a while – and only need to be redone when a sensor is moved or changed out.

-Harold Orlinsky, General Manager
Processing Multibeam Imagery in SonarWiz

Multibeam echo sounder (MBES) imagery has improved dramatically in recent years and each new version of SonarWiz has introduced improved tooling for working with these data. Most of SonarWiz’s image processing and targeting tools are now also available for MBES systems. In this article we will take a look at the two different approaches offered by SonarWiz for processing MBES image data.

A MBES image differs from traditional sidescan (see Figure 1). Each beam in a MBES is roughly equivalent to a complete side scan channel. To create an MBES image, the portion of the beam time series that corresponds to the bottom detection (also called a “snippet”) is extracted and placed along the beam footprint. The snippets from successive beams are pieced together to form the image across the swath.
Fig 1 - Formation of a sonar image from (A) multibeam and (B) side scan sonars.
The multibeam image is built by piecing together the time signal ("snippets") from each beam; the sidescan image is composed of a single time series. (after Lurton, 2020, figure 8.32)

The along-track resolution of MBES images is usually less fine than side scan sonars due to the wider beam apertures. While the quality of the reflectivity data is improved by the beam forming (less noise), the beam directivity patterns modulate the amplitude data making it more complicated to level the snippet intensity into a seamless image.

Finally, MBES are usually operated to optimize for bathymetry collection, so the systems maintain high angles of incidence with the seafloor. This makes it hard to detect microrelief that would be apparent in a side scan image collected close to the seabed at a high grazing angle. (Lurton, 2010)

SonarWiz currently supports two different workflows for processing MBES imagery: (1) convert the MBES imagery into a pseudo-side scan image; and (2) processing the intensity data on the bathymetric soundings. There are pros and cons to each approach.
Figure 2 - Waterfall views of MBES imagery.
Image constructed using (A) the Side Scan Engine at 4096 samples per channel, and (B) the Bathymetry Engine at 512 samples per channel.

When you import MBES imagery using the side scan engine (See Figure 2A) SonarWiz can display up to 4096 samples per channel (8192 samples across the whole swath). The resulting imagery can be very high resolution if the multibeam packets support it (for example: S7K Snippets, ALL or KMALL Time Series, R2 TruePix, etc.). Once the data is converted to side scan, the operator can take full advantage of SonarWiz’s powerful side scan processing tools.

This workflow is a fast way to process hundreds of track lines and is recommended for target detection and identification since it offers the highest possible image resolution. However, the SonarWiz side scan engine does not raytrace the samples to the seafloor and cannot accurately represent overhangs or other complicated topography. Nor can it handle unconventional sonar offsets. For these situations, we recommend using the bathymetry engine.

The second MBES image processing option in SonarWiz is to import the data using the bathymetry engine (see Figure 2B). In this mode, SonarWiz assigns a single intensity value to each beam in the ping. The user can select to use the beam amplitude assigned by the manufacturer or SonarWiz can process the snippet intensity data and replace the beam amplitude with a statistically computed best value. In either case, the across-track image resolution is limited to the number of beams in the ping.

The advantage of this approach is that each image pixel is located precisely in X, Y and Z. So there is no ambiguity in the position of targets. Image mosaics created in this mode are tightly aligned. For many applications, the across-track resolution of shallow water multibeam systems is so high, that there are still tens of image pixels per meter which is more than enough to create beautiful seafloor mosaics. In addition, the bathymetry data makes it possible to see the same targets in both shaded relief and intensity waterfalls side-by-side which can be a powerful new dimension to target detection.
Figure 3 - Side-by-side waterfalls from the same bathymetry file .
(A) shaded relief bathymetry; and (B) beam amplitude intensity.

Of course, it is possible to use both methods in a single SonarWiz project. Users with both the side scan and bathymetry modules can select the processing method that makes the best use of their data. Either way, we have tried to make the processing of intensity data easy and efficient, with few steps needed to produce a clean image. 

Reference
Lurton, X. (2010) An introduction to Underwater Acoustics: Principles and Applications. Second Edition. Springer, Heidelberg. pp. 362-363.

- David Finlayson, Chief Scientist
New A-B Change Detection Difference Plot for Sidescan

Creating a sidescan mosaic for a survey is easy. And doing a second survey is also easy. You can even use the same line plans, as the area is known. But what’s difficult is to find any differences between the two. A visual inspection will find new features, or if there if something moved. But imagine doing this for a huge survey area, a 1:10,000 boat sheet or an area like the Port of Los Angeles. This inspection would take a while, and subtle differences might be overlooked.

In the upcoming release, we created an automated tool to analyze two areas, creating a difference plot of items that changed. This can be done with either sidescan or backscatter, applying EGN or gains, creating a grid of the data from the amplitude. The standard deviation is calculated and amplitudes minus the mean are divided by the standard deviation on each grid. Then the grid with the smallest range is scaled and offset to match the grid with the largest range.

It requires a little bit of math, but we need to make sure we are comparing apples to apples and get all the data normalized. I imagine apples to oranges wouldn’t work too well. What we end up with is a Difference Grid. If the grids are at different resolutions, the smaller resolution is used for the difference grid.

When developing this tool, we tried different data sets and settings, and found there is no single threshold setting that works for all data sets. So there is a user threshold setting, which clips data less than the threshold as that of the background color, so that only those cells at or above the threshold retain their value and are visible.

Using the A-B tool (see image below)
  • The first image is the baseline survey (top left)
  • The second image is the second survey run (top right)
  • The normalized amplitude grid, overlaid with both data sets (bottom left)
  • Items of interest, shown with colored cells (bottom right)
So whether the end goal is to do a port security assessment – locating new features on the bottom; or an environmental impact study of changes – monitoring the growth of an invasive species; these comparisons and the automated tool will make your job a little easier.

As we continue to add new features to this module, I welcome your feedback to make this tool even better.

-Harold Orlinsky, GM and Howard Unkeles, Senior Developer
Forward Looking Sonar for Sidescan

We are adding support for Forward Looking Sonar (FLS) systems to SonarWiz 7.6. While the data for FLS systems look similar to other sonar systems such as Side Scan Sonar (SSS), FLS data is different and presents its own challenges.
Screen Shot of Pipeline Data Viewed in Kongsberg M3 Software
The FLS data is presented as a snapshot much like a video frame. It can be thought of as an acoustic video camera. This yields many frames per second resulting in a large amount of overlapping data. Each frame consists of multiple beams spread over the field of view (FOV).

These beams have an area of optimal focus. To allow the user to take advantage of this, SonarWiz allows the user to choose a sampling zone within the acoustic frames to import. Each of these sampled frames are then recorded and can be mosaiced and processed in SonarWiz.

Beyond simply using the FLS data to produce a mosaic, it can also be used to augment other types of sonar data. One such use is filling the Nadir gap present in most sidescan data. This can be accomplished using the transparency tools in SonarWiz.

SonarWiz 7.6 will be released with support for the Kongsberg M3 initially. Support for additional FLS systems will continue to be added in the near future.

-Chris Favreau, Program Manager
Dramatic improvements in 2D & 3D drawing

With the release of SonarWiz 7.5, Chesapeake introduced a drawing cache mechanism designed to allow for compact storage of, and quick access to, large bathymetric point clouds for display within the 3D viewer. This cache allows for much faster loading and drawing of large surveys by varying the level of detail shown to match the point of view, data loaded, and resources available.
Left: Recursive subdivision of a cube into octants. Right: The corresponding octree.

For SonarWiz 7.6, the drawing cache enhancements have been applied to the 2D plan view display, greatly improving drawing performance there as well. Previously, SonarWiz would draw bathymetry on the plan view by iterating through nearly the full set of data, regardless of zoom level, resulting in significant unnecessary work. Now, based on plan view resolution, data size, and user preferences, SonarWiz will adaptively read and draw only the data necessary.

In addition to drawing performance, use of the draw cache for plan view drawing allows for lower overall memory usage. In typical projects, SonarWiz will often use half or less of the memory used in prior versions.

The drawing cache in version 7.5 was built after a bathy merge process, and always built in full. In 7.6, the cache is incrementally updated after bathy editing, and updates are restricted to the areas changed, making this a much faster process overall. For large projects, the time between editing in the swath or area editors and seeing the results in the 3D and 2D views has been reduced in many cases from minutes to seconds.
Plan view of bathymetry data represented using octrees.
3D representation of bathymetry divided into octree nodes.
Drawing quality is improved in a couple of ways as well, both in the 3D viewer and in the 2D plan view. Better control over point sizes and level of detail is available, allowing you to favor drawing speed while working at the project overview level, but optimize for rendering quality for final output. In the plan view display, overdraw is better controlled,
taking into account the point of view, resulting in less jarring visible discontinuity at swath intersections.

Users with large bathy projects will notice the biggest improvements from these changes; roughly speaking, the larger the project, the larger the performance benefits.

- Jonathan Fleetwood, Development
SonarWiz 7.6 Webinar and Marketing Team Update

Our team   remains committed, as always, to supporting you and your work during these unprecedented times. We are implementing increasingly more virtual trainings and critical   resources regularly to help you maintain your usual work speed, while adjusting to a new workplace landscape.

To that end, our next webinar will be held on April 21st at 10 AM PT. We hope you will join us for an insights-packed hour, hosted by Chief Scientist, David Finlayson. Content will focus on sharing actionable advice to improve your efficiency and increase productivity, while highlighting the latest enhancements, and demonstrating how to:  

  • Process data from Forward Looking Sonar
  • Perform Multibeam Performance Testing
  • Easily identify variations using A-B Change Detection difference plotting
  • Handle more points than ever in the 3D View with LOD
  • Speedily draw bathymetry points with the 2D View

At the end of the webinar, David will carve out some time for a short Q&A period to address your questions. Please email us ahead of time with any questions you would like to be covered. We’ll do our best to answer each during the webinar, and if we cannot, we will provide answers to any remaining questions during a digital recap.

Can’t make that time but still want to learn? Not to worry - we’ll be sending out a recording you can view in your downtime.

We look forward to connecting with you and always welcome hearing from you with any ideas or feedback for additional ways we can best serve you during these difficult times. Stay well.

- Ashley Chan, Marketing
Chesapeake Customers in the News
 
SonarWiz software is used by many hundreds of clients worldwide, including NOAA, USGS, Fugro, Oceaneering, leading academic institutions, maritime archaeologists and many of the world’s navies. I am highlighting a few recent articles about the exciting work our customers are doing. As you can see below, SonarWiz is used for a wide variety of purposes across many industries as well as government, academic and non profit research.
 
AUTOMATION & ROBOTICS

Ocean Infinity launches  Armada , largest USV fleet .
US-based seabed survey and ocean exploration company Ocean Infinity said it has launched a new marine technology and data company boasting the industry's largest fleet of unmanned surface vehicles (USV).

First in Industry automated AUV survey in Angola with one surface vessel.
"The project was the first time that geophysical, geotechnical, and seismic data has been gathered at the same time," marine robotics and offshore survey specialist Ocean Infinity said.

ExxonMobil  awards Guyana contract to Ocean Infinity.
Ocean Infinity will simultaneously deploy a fleet of AUVs in water depths of between 70 meters and 2,150 meters over an area of approximately 3,100 square kilometers.
 
OFFSHORE WIND FARMS
 
Oceaneering to prepare seabed for  Moray East Wind Firm  in Scotland.
Offshore services company Oceaneering has won a contract to complete seabed route and debris clearance for the Moray East Wind Farm project in the Moray Firth, Scotland.

Fugro partners with  Korean survey  company to develop OFW.
Growing demand for alternative energy sources has led South Korea to explore its potential for wind energy, and Fugro’s global experience on over 100  offshore wind  farm projects will be key to realizing South Korea’s offshore wind farm ambitions.

DEFENSE

N-Sea Royal Dutch  Navy contract for mine countermeasures.
N-Sea announced a commencement of a five-year contract with the Royal Netherlands Navy

COASTAL MAPPING

Fugro signed a 5-year Indefinite Delivery Indefinite Quantity (IDIQ) contract with the US National Oceanic and Atmospheric Administration (NOAA) to provide shoreline mapping services in support of the agency’s Coastal Mapping Program.

RESEARCH

Scientists mapped Bikini Atoll nuclear bomb test craters.
Fox News  reported : “For the first time, scientists have conducted extensive mapping of the seafloor at Bikini Atoll, the remote Pacific Ocean testing site for atomic bombs between 1946 and 1954. The research was revealed Monday at the Fall Meeting of the American Geophysical Union in San Francisco. The study, authored by Arthur Trembanis, Ph.D., an associate professor at the University of Delaware and doctoral student Carter DuVal, describes the site as “the world's first simulated nuclear battlefield.”
 
MARITIME ARCHAEOLOGY
      
Project Recover locates three World War II aircraft, missing for 76 years.
Three aircraft associated with seven American servicemen missing in action from World War II were recently discovered in Truk Lagoon, now known as Chuuk State in the Federated States of Micronesia, by Project Recover partners from the University of Delaware and Scripps Institution of Oceanography, part of the University of California, San Diego.  Read more .

-Stephen D'Andrea, Business Manager
Greetings From the Other Side

No, not that side. I’m still alive and well but have retreated from day to day operations at Chesapeake. Eileen and I have been enjoying lots of biking, hiking and playing music. And why wouldn’t we? Harold’s got the business on solid ground and CTI is stronger than ever. At least, that’s what he tells me.

Like most of you, after almost 30 years in the business I’ve made a lot of good friends and special snowflakes. It’s what makes our industry so great. So, while you might not see me responding on support tickets as often please drop a line and say hi!

- John Gann, Co-Founder
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