Seafloor Mapping AUV MBARI has developed autonomous underwater vehicles (AUVs) with capabilities to map the seafloor with higher resolution than is possible with hull-mounted or towed sonar systems.There are now two AUVs optimized for meter-scale mapping in the MBARI fleet. The vehicles are equipped with four mapping sonars that operate simultaneously during a mission: a swath multibeam sonar, two sidescan sonars, and a sub-bottom profiler. The multibeam sonar produces high-resolution bathymetry (analogous to topography on land), the sidescan sonars produce imagery based on the intensity of the sound energy’s reflections, and the subbottom profiler penetrates sediments on the seafloor, allowing the detection of layers within the sediments, faults, and depth to the basement rock. All components are rated to 6,000 meters depth. The vehicles are launched on programmed missions and run on their own battery power until they return to the ship, as programmed, for recovery. Gallery In honor of MBARI’s long-time Board member Dr. D. Allan Bromley of Yale University, who passed away in 2004, the first Mapping AUV was christened the D. Allan B. Additional Information Purpose and motivation A fundamental activity in marine science is to use mapping technology to image the structure and character of the seafloor. Sonars that are hull-mounted or towed can provide high quality seafloor maps in shallow water, but cannot show details in seafloor features such as lava flows or slumps in typical ocean depths.Using platforms mounted with high-frequency sonars that can operate in deep waters is necessary to map the seafloor at high resolution. Since high-frequency sound is required to obtain high-fidelity maps of the seafloor, and high frequencies are attenuated by sea water, the sonar must be brought close to the seafloor to produce the highest quality maps. Platforms in the past have consisted of submersibles, which are expensive, noisy and erratic, or towed systems, which in deep water and especially near rough seafloor, can be dangerous and slow and produce data that is not precisely located and contaminated by ship motion. AUVs provide a faster, more nimble platform to produce very high-quality data sets especially in the deep ocean, and can accomplish this task efficiently and reliably.Development of the Seafloor Mapping AUV and software for processing the sonar data has been a major focus of the Seafloor Mapping Lab. New high-resolution maps of the seafloor are expected to:Drive new science (such as sediment transport from shelf to deep sea)Enable deep-sea resource management (such as habitat surveys)Help in planning & installing seafloor observatories (such as MARS)Provide spatial context for ROV dives and enables targeted sampling Vehicle specs General SpecificationsTwo Dorado- class autonomous underwater vehicle’s (AUV) designed and built by MBARISize: 0.53 meters (1.7 feet) in diameter; 5.3 meters (17.3 feet) longThree modular sectionsHull: ABS plastic farings held together by circular joining rings (acoustically transparent at the relevant frequencies and provides structural strength)Syntactic foam between housings provides buoyancyWeight: 680 kilograms in airEndurance: 19 hoursSpeed: 1.5 meters per second (5.4 kilometers per hour, or 3 knots)Depth rating: 6,000 metersAltitude: typically flown 50 to 100 meters above the seafloorInertial Navigation System (INS) and Doppler Velocity Log (DVL) navigationMaximum range: 95 kilometersTurning diameter: less than 20 metersDive and climb rates: typically 25 m/min descending and 50 m/min ascendingShip operations most often from MBARI’s R/V Rachel Carson but has been operated from other vessels ranging from a 24 m (80 ft) pilot boat to a 110 m (360 ft) icebreaker.AUV Nose:Conductivity, temperature, and depth (CTD) sensor (SeaBird SBE-49 fastCat)Water sound speed sensor10 kWhr of Lithium-ion batteriesAUV Mid-body Payload:Teledyne SeaBat T50-S 400 kHz Multibeam Sonar1.0 degree by 0.5 degree beams1024 beams across a 170 degree swathEdgetech 2205 Sonar Package110kHz chirp sidescan1-6 kHz chirp subbottom profilerAUV Tail:Kearfott SeaDevil Inertial Navigation System (INS) with integrated 300 kHz Doppler velocity log (DVL)Paroscientific Digiquartz pressure sensorMain vehicle computerUltra-short baseline (USBL) tracking sonar beaconBenthos acoustic modem for communicationsArticulated propeller inside a circular duct for propulsion and controlPower OptionsDual 5 kWhr lithium ion battery packs in spherical glass housingsPropulsion MBARI-patented propulsion systemBrushless DC motor and gear boxDouble-gimballed ring-wing duct moves vertically for elevator, and horizontally for rudderPropeller moves with the duct52 Newtons (12 lbf) of thrust at 300 rpmSurface CommunicationsFreewave RF modem, 57.6 kilobits per second.Two Iridium satellite modemsRadio Direction finder (RDF) beaconSubmerged communicationsSonardyne Ranger 2 USBL, 19 kHz down, 27 kHz upSafetySlight positive buoyancy (~8 pounds buoyant)Emergency 10 kilogram drop weight with internal and remote acoustic triggerHomerpro acoustic beacon, radio direction finder, strobe lightWhen on the surface, emails position via Iridium satellite network Deployment The AUV is usually deployed and recovered over the side of a ship using a crane. MBARI AUV technicians communicate by radio to the AUV while it floats at the ocean surface to download the mission script to it and check that all of the systems and instruments are fully functional. Then the AUV receives a command to dive.Once submerged it is no longer in contact with the global positioning system (GPS). The doppler velocity log (DVL) can lock onto the bottom when the AUV is within 130 m of the seafloor. In waters deeper than 130 m, the navigation of the AUV is updated on descent using ultra-short baseline (USBL) acoustic tracking from the ship until the DVL locks on to the sea floor. Then the inertial navigation system (INS) takes over, aided by the DVL. Since the AUV is programmed with its mission script, it is usually not tracked during the survey, which means the research vessel can conduct other tasks and recover the AUV at a later time period.When an articulating crane with a capture head is available, as on MBARI’s AUV mother vessel, R/V Rachel Carson, AUV recovery is accomplished by maneuvering the ship alongside the AUV and hooking into the lifting bale. Otherwise, a small boat may be used to bring the AUV to the ship, and manually hook the bale to the ship’s crane. Sonar The mapping AUV maps the seafloor by emitting sound at various frequencies that reflect off the bottom and return to receivers on the vehicle. The amount of time the sound takes to return and the energy with which it is returned are processed to make “images” of the shape and hardness of the seafloor. The vehicle is programmed to “mow the lawn” (moving back and forth across a segment of the seafloor) to fully cover a region of interest. There are three mapping sonar systems aboard the mapping AUV described belowMultibeam sonarThe primary mapping sensor is a Reson 7125 400 kHz multibeam sonar. It produces swath bathymetry and backscatter intensity. The bathymetry data is 1 meter lateral resolution in surveys flown at 50 meters altitude, and lower resolution if flown at higher altitudes. The vertical precision is 0.10 meters (limited by pressure sensor).Sidescan sonarThis map was generated from sidescan data collected in Monterey Canyon. Dark patches are areas of low reflectivity. © MBARI 2006Edgetech 110 kHz chirp sidescan sonar images the seafloor character such as surficial texture, near surface density variations and other fine-scale features at ~0.1 m resolution.Subbottom profilerEdgetech 1-6 kHz chirp subbottom profiler images subsurface sediment structure. It achieves up to 50 m penetration with 0.1 m vertical resolution. Navigation The current navigation system used on the mapping AUV is the Kearfott SeaDevil inertial navigation system (INS). It also includes the Doppler velocity log (DVL) as well as a ring laser gyro. If the DVL continuously tracks the seafloor, the real-time navigation deviation is 0.05% of the total distance traveled. The INS also provides data on the vehicle attitude (pitch, heading, and roll). The pressure sensor can precisely measure vehicle depth at a standard deviation of 0.1 meters up to 6000 m depth. Control algorithms use this data to maintain a stable platform and to record the vehicle’s track.Mission Planning and ExecutionFor the vehicle to fly at a safe and uniform altitude over the seafloor, missions are planned over the most reliable maps available, typically using bathymetry collected using ship-mounted sonars. The mission route is planned interactively in a visualization tool that is part of the MB-System software package.Deep water missions start on the surface where the vehicle obtains a valid global positioning system (GPS) fix and begins a spiral descent. Without DVL bottom lock, the INS drifts rapidly. In order to stabilize the INS position during decent, USBL tracking of the AUV by the ship is relayed to the AUV using the acoustic modem. Once the AUV is close enough to the seafloor that the DVL can measure velocity relative to the bottom, USBL aiding is no longer needed and is stopped. Once operational depth is achieved, the AUV starts the designed mission. Survey missions are typically composed of a sequence of straight lines that connect at waypoints.Navigation performanceThe navigation requirement for MBARI seafloor mapping operations is that the real-time navigation error at the end of the survey be no worse than half a swath width. This allows the navigation post-processing tool in MB-System,Mbnavadjust, to locate overlapping and crossing swaths. This tool matches bathymetric features in overlapping swaths and solves for a navigation model with relative precision equivalent to the lateral resolution of the bathymetry data. Team Directory Erik Trauschke Autonomous Systems Operations Manager Jordan Caress Dorado AUV Operations Engineer Randy Prickett AUV Operations Engineer Related Technologies Software MB-System Technology MB-System Open source software for processing and display of multibeam and sidescan sonar data. Instrument Wave Glider-Based Communications Hotspot Technology Wave Glider-Based Communications Hotspot An integrated system that enables autonomous devices to talk back. Related News News Mapping reveals rapid changes to the Arctic seafloor as ancient submerged permafrost thaws Press Release 03.14.22 News Seeing Sur Ridge: New animation transforms deep–sea mapping data to reveal the majesty of an underwater oasis News 03.01.21 News Hundreds of hydrothermal chimneys discovered on the seafloor off the Pacific Northwest News 04.28.20 News MBARI researchers join international research expedition to the Arctic Ocean News 09.14.22 News Unlocking the mysteries of the Arctic seafloor News 03.10.21 News Canyon up close: New animation drains Monterey Bay to uncover the beauty of its geology News 08.18.20 Publications All Publications Clague, D.A., J.F. Martin, J.B. Paduan, D.A. Butterfield, J.W. Jamieson, M. Le Saout, D.W. Caress, H. Thomas, J.F. Holden, and D.S. Kelley. 2020. Hydrothermal chimney distribution on the Endeavour Segment, Juan de Fuca Ridge. Geochemistry Geophysics Geosystems, 21: 1–12. https://doi.org/10.1029/2020GC008917 Gwiazda, R.H., C.K. Paull, D. Caress, C.M. Preston, S.B. Johnson, E. Lundsten, and K. Anderson. 2019. The extent of fault-associated modern authigenic barite deposits offshore Northern Baja California revealed by high resolution mapping. Frontiers in Marine Science, 6: 1–13. https://doi.org/10.3389/fmars.2019.00460 Paduan, J.B., R.A. Zierenberg, D.A. Clague, R.M. Spelz, D.W. Caress, G. Troni, H. Thomas, J. Glessner, M.D. Lilley, T. Lorenson, J. Lupton, F. Neumann, M.A. Santa Rosa del Rio, and C.G. Wheat. 2018. Discovery of hydrothermal vent fields on Alarcón Rise and in Southern Pescadero Basin, Gulf of California. Geochemistry, Geophysics, Geosystems, 19: 4788–4819. https://doi.org/10.1029/2018GC007771 Clague, D.A., D.W. Caress, B.M. Dreyer, L. Lundsten, J.B. Paduan, R.A. Portner, R. Spelz-Madero, J.A. Bowles, P.R. Castillo, R. Guardado-France, M. Le Saout, J.F. Martin, M.A. Santa Rosa-del Rio, and R.A. Zierenber. (2018). Geology of the Alarcon Rise, Southern Gulf of California. Geochemistry Geophysics Geosystems, 19: 807–837. http://doi.org/10.1002/2017GC007348 Clague, D.A., J.B. Paduan, D.W. Caress, W.W. Chadwick Jr., M. Le Saout, B. Dreyer, and R.A. Portner. 2017. High-resolution AUV mapping and targeted ROV observations of three historical lava flows at Axial Seamount. Oceanography, 30: 82–99. http://doi.org/10.5670/oceanog.2017.426 Maier, K.L., D.S. Brothers, C.K. Paull, M. McGann, D.W. Caress, and J.E. Conrad. 2016. Records of continental slope sediment flow morphodynamic responses to gradient and active faulting from integrated AUV and ROV data, offshore Palos Verdes, southern California borderland. Marine Geology, 393: 47–66. http://dx.doi.org/10.1016/j.margeo.2016.10.001 Paduan, J.B., D.A. Clague, D.W. Caress, and H. Thomas. 2016. High-resolution AUV mapping and ROV sampling of mid-ocean ridges. Marine Technology Society / Institute of Electrical and Electronics Engineers Oceans Conference, 2016: 1–8. http://dx.doi.org/10.1109/OCEANS.2016.7761264 Paull, C.K., S.R. Dallimore, D.W. Caress, R. Gwiazda, H. Melling, M. Riedel, Y.K. Jin, J.K. Hong, Y.G. Kim, D. Graves, A. Sherman, E. Lundsten, K. Anderson, L. Lundsten, H. Villinger, A. Kopf, S.B. Johnson, J. Hughes Clarke, S. Blasco, K. Conway, P. Neelands, H. Thomas, and M. Côté. 2015. Active mud volcanoes on the continental slope of the Canadian Beaufort Sea. Geochemistry, Geophysics, Geosystems, 16: 3160–3181. http://dx.doi.org/10.1002/2015GC005928 Paull, C.K., D.W. Caress, H. Thomas, E. Lundsten, K. Anderson, R. Gwiazda, M. Riedel, M. McGann, and J.C. Herguera. 2015. Seafloor geomorphic manifestations of gas venting and shallow subbottom gas hydrate occurrences. Geosphere, 11: 491–513. http://dx.doi.org/10.1130/ges01012.1 Clague, D.A., B.M. Dreyer, J.B. Paduan, J.F. Martin, D.W. Caress, J.B. Gill, D.S. Kelley, H. Thomas, R.A. Portner, J.R. Delaney, T.P. Guilderson, and M.L. McGann. 2014. Eruptive and tectonic history of the Endeavour Segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages. Geochemistry, Geophysics, Geosystems, 15: 3364–3391. http://dx.doi.org/10.1002/2014GC005415 Clague, D., B.M. Dreyer, J.B. Paduan, J.F. Martin, W.W. Chadwick, D.W. Caress, R.A. Portner, T.P. Guilderson, M.L. McGann, H. Thomas, D.A. Butterfield, and R.W. Embley. 2013. Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge. Geochemistry, Geophysics, Geosystems, 14: 4403–4443. http://dx.doi.org/10.1002/ggge.20240 Chadwick Jr., W.W., D.A. Clague, R.W. Embley, M.R. Perfit, D.A. Butterfield, D.W. Caress, J.B. Paduan, J.F. Martin, P. Sasnett, S.G. Merle, and A.M. Bobbitt. 2013. The 1998 eruption of Axial Seamount: New insights on submarine lava flow emplacement from high-resolution mapping. Geochemistry, Geophysics, Geosystems, 14: 3939–3968. http://dx.doi.org/10.1002/ggge.20202 Caress, D.W., D.A. Clague, J.B. Paduan, J.F. Martin, B.M. Dreyer, W.W. Chadwick Jr., A. Denny, and D.S. Kelley. 2012. Repeat bathymetric surveys at 1-metre resolution of lava flows erupted at Axial Seamount in April 2011. Nature Geoscience, 5: 483–488. http://dx.doi.org/10.1038/ngeo1496 Paull, C.K., D.W. Caress, W. Ussler III, E. Lundsten, and M. Meiner-Johnson 2011. High-resolution bathymetry of the axial channels within Monterey and Soquel submarine canyons, offshore central California. Geosphere, 7: 1077–1101. http://dx.doi.org/10.1130/GES00636.1 Paull, C.K., W. Ussler III, D.W. Caress, E. Lundsten, J. Barry, J.A. Covault, K.L. Maier, J. Xu, and S. Augenstein. 2010. Origins of large crescent-shaped bedforms within the axial channel of Monterey Canyon, offshore California. Geosphere, 6: 755–774. http://dx.doi.org/10.1130/GES00527.1 Paduan, J., D.W. Caress, D.A. Clague, C.K. Paull, and H. Thomas. 2009. High-resolution mapping of erosional, tectonic, and volcanic hazards using the MBARI mapping AUV. Rendiconti Online Società Geologica Italiana, 7: 181–186. Caress, D.W., H. Thomas, W.J. Kirkwood, R. McEwen, R. Henthorn, D.A. Clague, C.K. Paull, J.B. Paduan, and K.L. Maier. 2008. High-resolution multibeam, sidescan, and subbottom surveys of seamounts, submarine canyons, deep-sea fan channels, and gas seeps using the MBARI AUV D. Allan B.. Marine Habitat Mapping Technology for Alaska: 47–70.