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A Platform for Underwater Cartography Tool Development
VideoRay ROVs Can be Used as a Platform For Advanced Underwater Mapping Activities

By Andrew Goldstein
Director of Software Engineering
and

Marcus Kolb
Director of
Research and Development
VideoRay LLC
Phoenixville, Pennsylvania



The practice of cartography has evolved through the technological development of tools that allow for the collection of spatial or spatially correlated data sets. Improvements in instrumentation, from the groma to the theodolite to the cross staff to the global positioning system, have enabled the generation of more accurate and precise maps. New sensor technologies, such as in-situ mass spectrometers, allow for the creation of entirely new kinds of maps. New platforms allow for the mapping of previously inaccessible, uncharted territories. HC SVNT DRACONES...no longer.

Satellites, unmanned aerial vehicles and autonomous underwater vehicles (AUVs) are the most prominent examples of platforms that facilitate cartography.

Enabling the acquisition of large spatial data sets has been the primary driving force in the technological progress of these platforms. Satellites providing global-scale maps of climate patterns and autonomous gliders delivering ocean-scale data sets illustrate the current level of achievement.

Platforms and sensors provide for the acquisition of spatially correlated data. Geographic information systems (GIS) and geospatial visualization applications (such as Google Earth) make the presentation and analysis of these data easier than it has ever been.

The evolution of new cartographic systems—through the coupling of new sensors to innovative platforms, the development of new software analysis applications and the use of new operational methodologies—will extend the baseline of what is possible.

This stainless steel cage and stabilizer wing encloses a VideoRay Pro 3 ROV and multibeam sonar. Towed video survey techniques are used to map large areas.
Small ROVs as Cartographic Tools
Small remotely operated vehicles (ROVs) are often categorized by either their size (mini, micro, man-portable, etc.) or their operational role, most commonly as observation vehicles. The epithet “flying eyeball” is often used to describe their function as a means of extending the vision, or the observation ability, of the pilot. ROVs, and especially small ROVs, are less often considered in mapmaking missions than more traditional tools such as towed bodies, surface-vessel-mounted instrumentation, free swimming AUVs and satellite imagery.

ROVs in general do not provide the kind of large-scale spatial data set generation for which other technologies are known. Currently, ROVs have not typically been optimized for long-duration, unattended, large-area sampling. Of course, there are exceptions. ROVs have been used in long-distance pipeline surveys through live boat operations, and detailed photo-mosaics of ancient shipwrecks have been created by tethered vehicles under autonomous computer control.

However, while ROVs’ spatial range is limited by their tether, it also makes them unique underwater cartographic tools, providing real-time, high-bandwidth data. While the hydrodynamics of ROVs, particularly small ROVs, usually make them an inherently less stable acquisition platform than a towed body, this mobility is what allows for new and more dynamic acquisition methods.

One scenario where small ROVs have found acceptance is ship hull surveys for underwater inspection in lieu of dry docking or parasitic device detection. In these surveys, the end product is often a spatially correlated data set (a map).

Both platform and sensor development have been progressing as new technology is developed and integrated. ROVs have the mobility required to survey a hull easily (often facilitated by a hull-adhesion device), but they can also map more inaccessible regions of a ship, such as the running gear or sea chests. These areas are particularly challenging for other inspection techniques but comparatively easy for a small ROV. The need to redirect focus to an object of interest requires the real-time interactive features of a tethered vehicle. Significant development has already been done to enhance this capability, from application-specific navigation systems to custom single-task platforms.

Observation-class ROVs have typically been used to ground truth cartographic data obtained from other platforms, such as sonars or bathymetric sensors. They have been used to create maps through stochastic sampling video surveys or by the running of small-scale transects. However, there are many more opportunities for the furtherance of the art of cartography through the design of new tools. Encouraging the use of ROVs as a development platform will make these opportunities realities.


Cartography With the Pro 3 ROV
In addition to providing packaged solutions, VideoRay fosters the innovation of new technologies by providing both components (thrusters, tether, etc.) and open environments (hardware and software) for development. VideoRay encourages the creation of new instruments and sensors as well as unique platforms.

The VideoRay Pro 3 ROV has been customized by several academic and industrial research groups, with many focusing on converting the ROV into an AUV.

Replacing the human operator and tether with an embedded computer and power supply creates a platform which can be used in multiple roles: free swimming like a traditional AUV, tethered like a conventional ROV or as a hybrid combination.

The Laboratory for Underwater Systems and Technologies at the University of Zagreb developed an AUV conversion from their Pro 3, which included developing higher level tethered autonomous controllers and new sensor suites useful for mapping. A laser-and-video-analysis-based range finder was implemented on the vehicle, allowing for both automatic mensuration in the video and the autonomous maintenance of a fixed standoff distance from a target.

Dr. Chris Clark’s group at California Polytechnic State University, San Luis Obispo, has greatly advanced the state of the art in using micro-ROVs for mapping. Their use of the Pro 3 ROV in the sonar mapping of ancient cisterns highlights the ability of a VideoRay vehicle to reach previously inaccessible locations. They have also implemented new simultaneous localization and mapping software algorithms in order to create mosaic maps. The group performed additional custom development to integrate new positioning systems (State College, Pennsylvania-based KCF Technologies’ Smart Tether) and scanning sonar (Aberdeen, Scotland-based Tritech International’s Micron) in order to improve the accuracy of their maps, since a lack of localizable features often hinders mosaicking based on the sonar data alone.

One tool traditionally used for collecting seafloor cartographic data is the towed body. Towed bodies allow for relatively simple positioning using global positioning systems and layback calculations and a relatively high-speed mapping operation. Dr. Daniel Ierodiaconou of Deakin University has developed a custom wing and frame for the Pro 3 ROV to enhance stability, making a platform which can be used as a towed body or flown like an ROV. By alleviating lack of stability, this mechanical accessory addresses one of the primary complaints in using a micro-ROV for mapping.

Ierodiaconou’s dual platform can be used in a manner similar to traditional seafloor mapping methods while at the same time providing greatly enhanced mobility to “zoom in” on areas of interest in real time. In addition, Matthew Joordens, also at Deakin University, has developed control algorithms allowing multiple ROVs to be used cooperatively in concert to enable larger scale or reduced on-station-time mapping missions.

Moss Landing Marine Laboratories used the Pro 3 ROV and many other VideoRay technologies in the development of their Submersible Capable of Under Ice Navigation and Imaging vehicle, which is used for Antarctic ecosystem mapping. By taking bits and pieces of stable technology to speed up their custom engineering, they created an entirely new class of mapping vehicle optimized for this extreme environment.

Digital 3D map of a flooded cistern room in Malta utilizing scanning sonar data from a VideoRay ROV. (Image courtesy of Dr. Chris Clark, California Polytechnic State University)
The VideoRay Pro 4 Platform
The Pro 4 ROV greatly expands the possibilities for developing these types of customized systems in many ways.

In addition to supporting the widest variety of navigation sensors, there are several features of the Pro 4 ROV system that make it an attractive starting point for designing new mapping tools.

The Pro 4 is a small ROV with a single hydrodynamic float block and a clamshell skid that provides a standardized mounting platform and also houses a series of bronze ballast slugs. These mechanical improvements facilitate the adjustment of the buoyancy and trim of the vehicle while maintaining good flight characteristics when adding customized sensor payloads.

Simple electrical interfaces for power (stable 12 and 24-volt supplies), data communications (RS-485 and optional DSL Ethernet) and video facilitate the integration of external sensors.

Enabling Sensor Development. The main communication bus allows for the easy physical integration of subsystems, but it makes no provisions for channel sharing. This is left to higher layers in the communication protocol stack. To further reduce the development burden, an additional interface electronics device is available, called the protocol adapter multiplexer (PAM).

This small electronics module (38 millimeters by 38 millimeters) and associated software kit facilitates the development of new payloads that do not inherently conform to the communication bus.

The PAM acts as an interface adapter between the Pro 4 RS-485 bus and a secondary serial bus (RS-232, transistor-transistor logic or RS-485). Generic software on board the PAM handles all packetization, arbitration, handshaking, etc. The PAM provides a method of transparent integration with almost any low-bandwidth device.

Software Development Kits. The platform software consists of many pieces, including firmware running on the ROV, payloads and various accessory devices. On the host computer there are software libraries that can be used to write applications or enhance VideoRay Cockpit, the standard piloting interface. Open documented protocols and data formats make for easy data communication and export.

The software running on board the ROV and on accessory payloads developed using the PAM or other modules is based upon the same code library. This embedded software development kit is written in GNU C (using the winAVR compiler package). Individual embedded applications are statically linked against this library.


Conclusions
Starting with a flexible ROV base platform can dramatically accelerate development of customized solutions for various applications.

This translates into both time and direct cost savings, as well as decreased risk, through the use of previously fielded components.

Small ROVs like the Pro 4 and its commercial brethren are exceptionally attractive as research and development platforms. Their size and logistical ease of transport can allow them to more easily reach previously inaccessible locations. Their relative low cost allows them to reach engineers who would otherwise not be able to obtain a technological foundation so quickly.



Andrew Goldstein is the director of software engineering at VideoRay LLC and the manager of the university developer program. Before VideoRay, he was chief software developer and part owner of Desert Star Systems. He holds degrees in materials science engineering and computer science.

Marcus Kolb is the director of research and development at VideoRay LLC. He has been designing control systems for 25 years and has developed and holds many patents on microbiological analytical methods and instruments.



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