This article was written and placed for the Canadian Centre for Marine Communications of St. John's, Newfoundland.
Reprinted courtesy of Sea Technology
Spatial Visualization of the Marine Environment:
Canadian Software Showcased
By Andrew Safer
Halifax, Nova Scotia
Staggering advances in computer technology have enabled geologists, geophysicists, hydrographers and others who work in the marine environment to make use of huge data sets on their PCs. This capability which has evolved over the last several years has created a significant demand for software that converts gigabyte and terabyte data sets into meaningful visual images.
This article highlights applications of 2 ½ D and 3D visualization software developed by several Canadian firms which collectively serve a diverse customer base including: pipeline and cable route surveyors, geologists, geophysicists, hydrographers and technicians who deploy remotely operated vehicles in the deep ocean. The Canadian Centre for Marine Communications (CCMC) of St. John's, Newfoundland (www.ccmc.nf.ca) is an umbrella organization that supports leading-edge technology development among Canadian firms. Having sponsored the research and writing of this article, CCMC has been instrumental in identifying the software development companies profiled here.
Commonly pictured by a color contour map, "2 ½ D" refers to a visual representation made up of x and y locational axes, and a z-axis representing depth, salinity, reflectivity or some other value. This type of image shows depth and offers the ability to profile, or show a cross-section. In a "3D" image, however, the objects, which are separated by space, can be viewed from any angle, including from the underside. Multiple data sets are often represented in these multicolor images.
These "pretty picture" visualizations communicate the meaning of the data to non-technical people, whereas they enable technical people to analyze, interrogate, edit and run "what if" scenarios. A key feature is improved analysis which has become infinitely easier than in the old days, when images were static and disconnected from the data.
Spatial visualization software is also enabling end users to work far more efficiently than in the past. "Now, we are collecting complete surfaces from source data (multibeam, LIDAR, RADARSAT, etc.)," explains Herman Varma, Head of Cartographic Research for the Canadian Hydrographic Service at the Bedford Institute of Oceanography. "Rather than having to extrapolate polygons by hand digitizing sparse data sets, we can generate on-the-fly contours, or polygons, from complete surfaces. If I want a two-meter contour," he says, "I'll set the specifications and let the visualization deliver it to me." He adds that tiling, as opposed to gridding, makes it possible to store the data in compact structures.
Varma's uses HH Viewer, a 3D visualization tool developed by Helical Systems of Dartmouth, Nova Scotia (www.helical.ns.ca). Looking at an image of a shipwreck in the Netherlands, he points to the high resolution of the shipwreck, and the low resolution of the surrounding area. The ability to fuse high- and low-resolution data in a single image enables him to provide the detail where it's needed, but not overtax the system with more data than is required. Looking at a spike poking up from the body of the vessel, he points to a tiny silhouette in the shadow. "The hydrographer would remove that thinking it's an outlier," Varma explains, "but because of the shadow, you can see it's a mast."
Varma also uses HH Viewer to model the coastal-erosion effects of storm surges on Prince Edward Island. The Canadian Hydrographic Service installed tide stations at various points on the Island to establish baselines for the highest high water level, lowest low water level and mean water level. The model shows the effects of storm surges that raise the high water mark by, say, 15 feet, which partly submerges the island. One feature of the tool is that it allows him to edit the underlying data and then view the re-computed image. Varma says the coastal-erosion modeling should be of interest to insurers, and to municipalities which could act to avert disaster.
Phil Scadden, Data Manager for the Institute of Geological and Nuclear Sciences in Wellington, New Zealand, uses HH Viewer to spot errors in maps of the seafloor. "It allows us to take cross-sections through the data set," he explains. "Sometimes the cleaning process will track incorrectly, and flag the data as bad. This allows us to resolve those kinds of errors because we can see it in a 3D view."
Whereas the raison d'etre of the first 3D tools was to provide "pretty pictures", by enabling the user to query a database (or databases), current 3D tools have evolved additional benefits.
The "Fledermaus" is a 3D tool that enables the viewer to fly through data and see it from all angles using a six-degree-of-freedom mouse. It was developed by Interactive Visualization Systems (www.ivs.unb.ca), a company that was spun off to the private sector out of the Ocean Mapping Group at the Fredericton-based University of New Brunswick in 1995. "Computer processing has allowed us to go from one frame of pixels to interactively explore data in real time," observes General Manager Lindsay Gee. "Before, we used to 3D render overnight, using big computers. But now with the games market driving the hardware, it's so much more useful than before."
Marine Geologist Jim Gardner, Chief of Pacific Seafloor Mapping for the US Geological Survey in Menlo Park, California, uses the Fledermaus to do geological interpretations onscreen. "It's an intuitive view of massive amounts of data," he exclaims. "I can smoothly progress right through the data sets looking at the highest resolution, and I can process it on screen, and interrogate. What's the acoustical backscatter, what are the volume calculations?" Identifying sediment waves of a certain height and length in a zone of low backscatter, for example, might point to a 90 per cent probability of finding mud. Other metrics might point to sand of a particular grain size. Gardner points out there is "a great need" to identify benthic habitats on the seafloor.
After a landslide caved in the western wall at Lake Tahoe, using the Fledermaus, Gardner was able to demonstrate that the site had collapsed. What made the difference was the ability to measure distances, heights and volumes. "Without being able to measure," says Gardner, "it would have been much more difficult."
In the pre-Fledermaus days, he would have created mosaic images on a computer, then lay them on a table, put a piece of tracing paper over it, trace the outlines of the features and then digitized the outline. "It took weeks to do what I can do in a day now," Gardner recalls, "and I was always looking at a 2D view back then."
Another application for Fledermaus is pipeline and cable route surveying. Art Kleiner, Chief Hydrographer of C& C Technologies, Inc. of Lafayette, Louisiana, has been using the Fledermaus software for three years and he praises it as a "great QC tool". On board the survey vessel, C&C's clients can use the Fledermaus to develop the route from the multibeam data as soon as it is generated which eliminates the need to come back for additional surveys later.
"Using traditional methods," Kleiner explains, "the survey would be brought back to the office and the geophysicist or geologist might say, 'This is no good. Go back and do this part again.'"
As previously noted regarding Helical's HH Viewer, the Fledermaus makes it easy to spot errors in the data. C&C's process is to gather the data with an EM 3000D (which collects 2,000 soundings per second). Using extensive algorithms, computer workstations eliminate 99.9 per cent of the errors. The remaining 0.1 per cent is represented by 30,000 to 50,000 soundings on one sheet. By looking at the data in 3D with Fledermaus, C&C technicians are quickly able to identify the errors which stand out in relation to their surroundings. Kleiner emphasizes the importance of being able to see the data in great detail. "A lot of times, with multibeam data, it's like looking at a picture of a movie star-you don't see all the wrinkles. With this, you see all the details that exist in the data."
2 ½ D Applications
For Geological Survey of Canada Geophysicist Ron Macnab, the beauty of spatial visualization is that it enables him to see multiple data sets at the same time. "Interpretation is greatly enhanced when your eye can draw inferences between the data sets," he says. "In earth sciences, it still comes down to: What can the trained interpreter see in the patterns? It's the relationships between patterns that is most significant."
Macnab is demonstrating the old method, which is to look at data sets represented graphically on three separate maps (in this case, of the Arctic), which, collectively, the geophysicist interprets. The first map shows the shape of the seabed, the second shows the magnetic anomaly (measure of the magnetization of the rock beneath the seabed), and the third shows the gravity anomaly (caused by density variations in the rock beneath the seabed).
By looking at the magnetic stripes caused by seafloor spreading on the second map, and combining that with the shape of the ocean floor from the first map, for example, he learns that different regions of the Arctic Ocean have different geological histories.
Macnab compares this time-consuming and painstaking method to the use of CARIS LOTS, a software package that was specifically designed by Caris of Fredericton, New Brunswick (www.caris.com) to assist coastal nations in delineating their maritime boundaries. According to Article 76 of the 1982 United Nations Convention on the Law of the Sea, maritime nations may assert rights over mineral and certain biological offshore resources located beyond their 200 mile limit. The deciding factors are the depth of the water and the thickness of the sediment in the area in question.
Rather than having to eyeball three separate maps, Macnab, who has been working on Article 76-related projects for over ten years, is able to view all of the relevant data for the Arctic (in this case) on one screen. He can query any point on the map for detailed information about depth or sediment type, and a cross-section appears along with the data onscreen, alongside the contour map. "I can zoom in and interact with the data," he explains. "It's mindbogglingly economical in terms of both time and frustration."
What Macnab appreciates most about modern software such as LOTS is the ready access to data that it offers, the ability to run "what if" scenarios and quickly prove or disprove a theory, and the overall ease of use. He adds that LOTS is set up to archive files which makes it easy for nations to justify their claims to the experts.
After the Swissair Flight 111 crashed in Nova Scotia waters in September of 1998, the Canadian Hydrographic Service conducted a multibeam survey of the site in order to use the imagery as a chart to guide the wreckage recovery effort. Working in partnership with CHS, the Geological Survey of Canada converted the survey into a format that would integrate with its "Regulus II" shipboard navigation system which had already been adapted for this use. Regulus II is software developed by ICAN of St. John's, Newfoundland (www.ican.nf.net). The end result was a system that enabled the recovery team to be certain they were systematically covering the entire seafloor in the 2.13 x 2.2 nautical-mile area. They dragged for wreckage in every location that showed indications of possible debris.
Geological Survey of Canada Engineer Dave Heffler who was assisting the onboard effort explains: "We used Regulus II to display where the ship and towed body were with respect to the brand new image of the seafloor." (The towed body was a laser linescanner that was deployed by Coastal Systems Station of the US Naval Warfare Center in Panama City, Florida .) "It shows that if the sensor missed the target, you know you need to make another pass."
Before this, Heffler had used Regulus II in conjunction with an ORE Track Point II acoustic positioning system to identify the location of a towed body (towfish) with respect to the ship. The system displays the towfish in 2 1/2D. "Without it," he says, "we wouldn't get as much information from our surveys. We wouldn't know where the samples came from as accurately because we wouldn't know exactly where the sampler is with respect to the features of the seafloor."
An application of a different sort enables Oceaneering International to train ROV operators, using "VROV" simulators at its facilities in Scotland, Norway, and Louisiana. VROV (Virtual Remotely Operated Vehicle), developed by Geo-Resources Inc. of St. John's, Newfoundland (www.grisim.com), is software that operates through an actual ROV control console to simulate a 3D underwater environment and the ROV as it flies through it. Interactive currents, equipment, terrain, and dirt/seasnow are displayed to simulate real-world conditions.
Oceaneering uses ROVs for oilfield work (for example, turning valves), cable burial, and blackbox recovery. Prior to adopting VROV, Oceaneering had been training operators in a small test tank "It was unrealistic," says Technical Manager (Aberdeen) Mark Philip. "It was so small it was very difficult to really fly around especially with the larger work class ROVs." In addition, the company sent new hires out to train at the jobsite. "The customers were understandably less than keen about this but we had little option if we wanted to train our people," he recalls.
With VROV, the trainee first learns how to maneuver the ROV in the basic directions by pressing buttons and moving levers. Next he learns navigation, getting to the jobsite, and flying around without becoming entangled in the tether.
Considering the ever-increasing power of the computer chip, the development and further refinement of high-end visualization software, and continual improvements in database integration, one wonders where all this is heading. Lindsay Gee of Interactive Visualization Systems observes: "Maybe a 3D chart is the future."
Robbert van Eijle, president of Indusol Industrial Control Ltd. of Ste-Ursule, Quebec has been developing one over the past year. He adds that, unlike with ECDIS, in the 3D display mode, objects will become smaller as distance increases. In a glance, this will afford the mariner an intuitive sense of the positioning of the objects on the chart. The mariner's perspective will be as if he were flying in a helicopter above and behind the ship, seeing the ship and the world as it really is. The other key element, says van Eijle, will be to show a real-time model of the seafloor (using S57 chart data) which will be seen through a simulation of the semi-transparency of the water. Varying degrees of "safe" and "unsafe" depth conditions will be indicated by coloring the model of the seafloor with the standard IMO colors.
While much of the marine world is wrestling to perfect 3D visualization capabilities, Herman Varma points out that the fourth dimension is time, which means that we can anticipate animation as the defining characteristic in 4D visualization. This will enable the viewer to witness, for example, sea level change and the attendant coastal erosion, over time.