QTC VIEW Research Articles

Determination of the distribution of shallow-water seagrass and drift algae communities with acoustic seafloor discrimination.

The spatial distribution of seagrass and algae communities can be difficult to determine in large, shallow lagoon systems where high turbidity prevents the use of optical methods like aerial photography or satellite imagery. Further complications can arise when algae are not permanently attached to the substratum and drift with tides and currents. A study using acoustic seafloor discrimination was conducted in the Indian River Lagoon (Florida, USA) to determine the extent of drift algae and seagrass. Acoustic surveys using the QTC View V system based on 50 and 200 kHz transducers were conducted near Sebastian Inlet. Results indicate that areas of seagrass can be identified, and are mixed with a high abundance of drift algae. Nearest-neighbor extrapolation was used to fill in spaces between survey lines and thus obtain spatially cohesive maps. These maps were then ground-truthed using data from towed video and compared using confusion matrices, The maps showed a high level of agreement (60%) with the actual distribution of algae, however some confusion existed between bare sand and algae as well as seagrass.

Evaluation of WorldView-2 and acoustic remote sensing for mapping benthic habitats in temperate coastal Pacific waters

Maps of nearshore marine habitat are fundamental tools for the management and conservation of coastal ecosystems. While traditional field mapping techniques, such as towed video and diver surveys, are still commonly employed for generating highly detailed maps of seafloor habitat, acoustic and satellite remote sensing have proven to be efficient alternatives for generating habitat maps. To date remote sensing using satellite imagery has dominated mapping efforts over coral reefs and other tropical ecosystems with fewer studies applied in temperate marine regions where acoustic studies are more common. Few studies exist that have assessed the performance of high resolution satellite imagery in mapping seafloor habitat in temperate regions. This paper compares the efficacy of high resolution satellite imagery (WorldView-2) and a single-beam acoustic ground discrimination system (QTC View V) for mapping the distribution of submerged aquatic vegetation at a site within the Gwaii Haanas National Marine Conservation Area (GHNMCA) off the north coast of British Columbia, Canada. Ground-truth data for training and validation were collected using a towed underwater video camera. Prior to classification the WorldView-2 image (8 bands, 2m resolution) was processed following orthorectification, atmospheric correction, glint correction, land and optically deep water masking. An acoustic survey was conducted using a 200kHz echosounder and data were processed and interpolated using QTC IMPACT software. The WorldView-2 imagery performed best in mapping habitat in regions shallower than 3m, obtaining a total accuracy 75%, where it could identify the distribution of green algae (Ulva spp.), brown algae (Fucus spp.) and eelgrass (Zostera marina). The 200kHz data were unable to detect the distribution of brown and green algae but were able to map the distribution of eelgrass as well as a subtidal red algae (Chondrocanthus exasperatus) (total accuracy 80%). A final habitat map containing all habitat types present at the study site was produced using the output from both datasets. The study resulted in recommendations for remote mapping of submerged vegetation in temperate coastal area.

Characteristic properties of seabed fluvial-marine sediments in front of Damietta promontory, Nile Delta, Egypt

Acoustic bottom classification utilities have been developed in favor of routine investigation of the seabed texture and grain size, as well as type of sediments. Single beam echosounder, seabed classification systems and QTC VIEW series V were used to map out and identify sediment gradients offshore Nile Delta in front of Damietta promontory. The survey area has an asymmetric shape and of very gentle slope parallel to the shore line at Damietta promontory. Ground truth observation analyses were carried out for 24 grab samples using the classification technique. The acoustic survey data were analyzed with the QTC IMPACT software and classified into five acoustic classes namely (silty clay, clayey silt, silt, sandy silt and very fine sand). The fine sediments (clay and silt) cover the front area of Damietta outlet, forming a stream like shape cutting the center of the area of study, which composed mainly of fluvial sediments. While the sandy sediments, appear as small patches to the east and west. The dominant of the small mean size (fine fractions) is corresponding to the fluvial depositions that form the Nile Delta fan of mainly mud sediments. Actually, since the building of Aswan High Dam in 1964, sediment discharge at the Nile promontories has diminished to almost zero, the recent situation of seabed characteristics is related mainly to the effect of the oceanographic circulation regime dominating the study area.

Benthic habitat mapping: Concerns using a combined approach (acoustic, sediment and biological data)

Near-shore benthic biotopes, in the 2–30 m depth range, were analyzed and mapped using a combination of biological, sedimentary and acoustic data to interrogate the utility of these methods. The surveyed area covered approximately 270 km 2, along 80 km of the Southeast coast of Portugal. The acoustic data were acquired with a single beam ground discrimination system (QTC VIEW, Series V), connected to a dual frequency echo sounder (50 and 200 kHz). Sediment grain size and macrofaunal community data were obtained by grab sampling at 88 sites. The sedimentary and the biological data were subjected to classification and ordination analysis and the acoustic data obtained with the two frequencies were analyzed individually with the QTC IMPACT (v3.4) software and classified into acoustic classes. The affinity groups obtained with the three datasets were mapped using a Geographic Information System. The study area showed an inshore-offshore pattern with sands ranging from very fine to very coarse, revealing a sediment distribution in the near-shore shelf comprised by two main areas; a very fine/fine sand area up to 7–10 m depth and a very coarse/coarse sand area offshore. In turn, the biological data also showed an inshore-offshore pattern, identifying two main biological assemblages: fine/very fine sand and coarse/very coarse sand communities. Furthermore, the biological pattern clearly reflected the hydrodynamic conditions of the area, from highly hydrodynamic shallow depth to the calmer deeper areas. Accordingly, species richness and densities were lower at shallow areas than at deeper depth. The acoustic data identified the prevailing biosedimentary gradients along the inshore-offshore direction. Overall, the results obtained here showed that the acoustic system could identify two main areas based on sediment grain size, which closely related to the two main biological communities (groups A and B). This study indicates the importance of combining several layers of information in order to increase the spatial resolution of the main biotope distribution (validating the acoustic data) and detail their sub-divisions (ground-truth sampling). Furthermore, we show that designing ground-truth samples on the basis of the acoustic diversity data allows the biological data to “speak” for itself. In general, acoustic techniques are used as a means to optimize ground-truth sampling. This will only be valid if acoustics can capture all the essence of biotope heterogeneity. If this is not the case, special attention should be given when using broad scale methods (acoustic remote sensing) devoted to biotope mapping.

Quantitative experimental comparison of single-beam, sidescan, and multibeam benthic habitat maps

Abstract Schimel, A. C. G., Healy, T. R., Johnson, D., and Immenga, D. 2010. Quantitative experimental comparison of single-beam, sidescan, and multibeam benthic habitat maps. – ICES Journal of Marine Science, 67: 1766–1779. Map comparison is a relatively uncommon practice in acoustic seabed classification to date, contrary to the field of land remote sensing, where it has been developed extensively over recent decades. The aim here is to illustrate the benefits of map comparison in the underwater realm with a case study of three maps independently describing the seabed habitats of the Te Matuku Marine Reserve (Hauraki Gulf, New Zealand). The maps are obtained from a QTC View classification of a single-beam echosounder (SBES) dataset, manual segmentation of a sidescan sonar (SSS) mosaic, and automatic classification of a backscatter dataset from a multibeam echosounder (MBES). The maps are compared using pixel-to-pixel similarity measures derived from the literature in land remote sensing. All measures agree in presenting the MBES and SSS maps as the most similar, and the SBES and SSS maps as the least similar. The results are discussed with reference to the potential of MBES backscatter as an alternative to SSS mosaic for imagery segmentation and to the potential of joint SBES–SSS survey for improved habitat mapping. Other applications of map-similarity measures in acoustic classification of the seabed are suggested.

Comparison of a Self-Processed EM3000 Multibeam Echosounder Dataset with a QTC View Habitat Mapping and a Sidescan Sonar Imagery, Tamaki Strait, New Zealand

A methodology for automatically processing the data files from an EM3000 multibeam echosounder (Kongsberg Maritime, 300 kHz) is presented. Written in MatLab, it includes data extraction, bathymetry processing, computation of seafloor local slope, and a simple correction of the backscatter along-track banding effect. The success of the latter is dependent on operational restrictions, which are also detailed. This processing is applied to a dataset acquired in 2007 in the Tamaki Strait, New Zealand. The resulting maps are compared with a habitat classification obtained with the acoustic ground-discrimination software QTC View linked to a 200-kHz single-beam echosounder and to the imagery from a 100-kHz sidescan sonar survey, both performed in 2002. The multibeam backscatter map was found to be very similar to the sidescan imagery, quite correlated to the QTC View map on one site but mainly uncorrelated on another site. Hypotheses to explain these results are formulated and discussed. The maps and the comparison to prior surveys are used to draw conclusions on the quality of the code for further research on multibeam benthic habitat mapping.

Estuarine Habitat Assessment for Construction of a Submarine Transmission Line

The present paper describes a submarine survey using the acoustic discrimination system QTC VIEW (Series V) as an exploratory tool to adjust final route alignment of a new pipeline. By using acoustic sound survey as an exploratory tool described in this paper to adjust final route alignment of a new pipeline to minimize the environmental impact caused and ultimately to avoid any mitigation measures. The transmission pipeline extended from the shore line of Abu-Qir Bay, on the Mediterranean Sea in Egypt, out to 70 nautical miles at sea (60 m water depth). Four main surface sediment types were defined in the study area, namely fine sand, silty sand, silt and clay. Results of the acoustic classification revealed four acoustic classes. The first acoustic class corresponded to fine sand, absence of shell debris and very poor habitats characteristics. The second acoustic class is predominant in the study area and corresponds to the region occupied by silt. It is also characterized by intermediate diversity of macrobenthic invertebrate community which is mainly characterized by polychaeta. The third acoustic class is characterized by silt to silty clay. It is characterized by a high diversity of macrobenthic invertebrate community which is mainly polychaeta with an intermediate diversity of gastropoda and bivalvia. The final acoustic class is characterized by clay and high occurrence of shell debris of gastropoda, bivalvia and polychaeta.

Remote sensing of underwater vegetation using single-beam acoustics

Abstract Quintino, V., Freitas, R., Mamede, R., Ricardo, F., Rodrigues, A. M., Mota, J., Pérez-Ruzafa, Á., and Marcos, C. 2010. Remote sensing of underwater vegetation using single-beam acoustics. – ICES Journal of Marine Science, 67: 594–605. A single-beam, acoustic, ground-discrimination system (QTC VIEW, Series V) was used to study the distribution of underwater macrophytes in a shallow-water coastal system, employing frequencies of 50 and 200 kHz. The study was conducted in Mar Menor, SE Spain, where the expansion of Caulerpa prolifera has contributed to the silting up of the superficial sediments. A direct relationship was identified between algal biomass and sediment-fines content. Acoustic information on sediment grain size and data on algal biomass were obtained in muddy and sandy sediments, including vegetated and non-vegetated seabed. Non-vegetated muddy areas were created by diving and handpicking the algae. The multivariate acoustic data were analysed under the null hypotheses that there were no acoustic differences between bare seabeds with contrasting superficial sediment types or among low, medium, and high algal-biomass areas, having in mind that grain size can act as a confounding factor. Both null hypotheses were rejected, and the results showed that 200 kHz was better than 50 kHz in distinguishing cover levels of algal biomass. The relationship between the 200-kHz acoustic data and algal biomass suggests utility in modelling the latter using the former.

Single-beam acoustic ground discrimination of shallow water habitats: 50 kHz or 200 kHz frequency survey?

The single-beam acoustic ground discrimination system QTC View, Series V, was used in the Bay of Cadiz, Southwest Spain, for the identification and mapping of the bottom acoustic diversity. The acoustic data were obtained through two successive surveys, each conducted with one of the following echo sounder frequencies: 50 kHz and 200 kHz. The performance of each survey frequency for the identification of the sedimentary gradients was analyzed. The surveys were conducted during high tide given that the majority of the surveyed area is shallower than 5 m, although depth may occasionally reach 20 m in specific areas located in a navigation channel. The acoustic data obtained at the two different frequencies were, individually, submitted to manual clustering and a final solution consisting of three acoustic classes was reached for both datasets. However, only the geographical distribution of the acoustic classes obtained with 50 kHz echo sounder frequency was coincident with the spatial distribution of the superficial sediment groups (silty medium sand, very silty fine sand and mud), identified through multivariate analysis of the grain-size data of ground-truth sediment samples. The results obtained with the 200 kHz echo sounder frequency did not match the sedimentary gradients obtained for the area surveyed, not even the separation of muddy and sandy areas.

Sedimentary facies of the eastern Pacific's northernmost reef-like setting (Cabo Pulmo, Mexico)

Cabo Pulmo, Mexico, is often cited as the eastern Pacific's northernmost coral reef. We investigated sedimentary dynamics to verify whether the system functions sedimentologically as a reef, which would mean that it retained internal sediment in a framework and exported peri-reefal sediment creating clearly identifiable facies dominated by reefal fauna. We mapped distribution of sediments using grab samples, the acoustic ground-discrimination systems QTC View and Echo plus at 50 kHz signal frequency and an IKONOS satellite image. Morphologically, the bay of Cabo Pulmo can be divided into intrusive dikes and rocky hardgrounds in less than 10 m depth and a sandy interior with rocky outcrops sloping to over 40 m. Reefal fauna without lasting framework-building but with production of typically reef-associated carbonate sediments, as well as a patch-reef facies were found on the dikes and hardgrounds. Sediments in the bay were a mixture of carbonates and siliciclastics and were influenced by a seasonal river near the bay's center that imported siliciclastic material. To the north and south sediments had a higher carbonate content, although overall the bay was characterized by > 50% siliciclastics. The shallower subtidal sands were dominated by mollusk fragments, whereas in depths > 30 m planktonic foraminiferal sand was found. Acoustically and optically remote-sensed maps were used to differentiate between the rocky and sandy areas and to identify the presumed off-shelf transport pathway of reef-derived carbonates. Overall, the sedimentary system is characterized by carbonate production, but the coarser reef derived carbonates (coral and reef-dwelling mollusks) are transported off-shelf along a steep depth gradient and little typical peri-reef sediment remains. This transport is likely aided by storms. Since no sediment retaining frameworks are formed, the dikes cannot retain internal sediment, and the reefal fauna was not dominant in sediments throughout the bay, we conclude that Cabo Pulmo sedimentologically functions only in a limited way like a coral reef.

Sea-bottom classification across a shallow-water bar channel and near-shore shelf, using single-beam acoustics

An acoustic ground discrimination system (QTC VIEW, Series IV) was used to identify and map the bottom acoustic diversity in the bar channel of Ria de Aveiro, Western Portugal. The majority of the survey area presented shallow depth for this type of equipment, ranging mainly from 5 to 15 m. Depth occasionally reached 25 m in specific areas located across the entrance channel, dug by the strong tidal currents, reaching 3 m/s. The acoustic data were submitted to manual and auto-cluster and the results obtained from both procedures were coherent. Using aids to the acoustic classification and ground-truth sediment data, a final solution consisting of four acoustic classes was reached. Their geographical distribution was coincident with the spatial distribution of the major bottom types and sediment groups (hard bottom, coarse sand, medium sand and fine sand), identified through multivariate analysis of the grain-size data, and reflected the complex hydrodynamics of the entrance channel. The acoustic pattern was coincident at the intersections of the acoustic survey lines, assuring the repeatability of the acoustic procedure. Overall, the acoustic approach showed consistent results for the assessment and mapping of the benthic habitats in this shallow-water coastal area, providing a very valuable tool in an area where conventional sediment sampling is less favourable, namely due to strong tidal currents and frequent ship traffic, such as the entrance channel of Ria de Aveiro and the near-shore adjacent shelf.

Detection of shallow subtidal corals from IKONOS satellite and QTC View (50, 200 kHz) single-beam sonar data (Arabian Gulf; Dubai, UAE)

We compared the results of seafloor classifications with special emphasis on detecting coral versus non-coral areas that were obtained from a 4×4-m pixel-resolution multispectral IKONOS satellite image and two acoustic surveys using a QTC View Series 5 system on 50 and 200 kHz signal frequency. A detailed radiative transfer model was obtained by in situ measurement of optical parameters that then allowed calibration of the IKONOS image against in situ optical measurements and a series of ground-truthing points. Eight benthic classes were distinguished optically with an overall accuracy of 69% and a Tau index T of 65. The classification of the IKONOS image allowed discrimination of three different coral assemblages (dense live, dense dead, sparse), which were confirmed by ground-truthing. Data evaluation of the acoustic surveys involved culling of datapoints with <90% confidence and <30% probability, two QTC-provided statistics, and the deletion of data classes without clear spatial patterns (visualized by single-class trackplots). The deletion of these ubiquitous classes was necessary in order to obtain any clearly interpretable spatial pattern of echo classes after the surveys were resampled to a regular grid and areas between the lines interpolated using a nearest neighbor algorithm. The 50 kHz acoustic seafloor classification was able to determine two classes (unconsolidated sand versus hardground) but was not able to determine corals. The 200 kHz survey determined high rugosity (=corals and sand ripples) versus low rugosity (=flat areas) but was not able to determine consolidated and unconsolidated sediments. Classes were extrapolated to the entire grid and polygons obtained from the two surveys were combined to provide maps containing four classes (rugose hardground=coral, flat hardground=rock, rugose softground=ripples and algae, flat softground=bare sand). Compared with the classification map derived from the IKONOS image, they were 66% accurate ( T=59) when the most highly processed data (only selected classes, >90% accuracy and >30% probability) were used, and 60% accurate ( T=53) when less processed data (selcted classes only, all data) were used. Accuracy against ground-truthing points of the most highly processed dataset was 56% ( T=46). These results indicate that results from optical and acoustic surveys have some degree of commonality. Therefore, there is a potential to produce maps outlining coral areas from optical remote-sensing in shallow areas and acoustic methods in adjacent deeper areas beyond optical resolution with the limitation that acoustic maps will resolve fewer habitat classes and have lower accuracy.

Acoustic detection of a scallop bed from a single-beam echosounder in the St. Lawrence

Abstract Single-beam seabed echoes combined with epi-macrobenthos photographs were used to remotely detect a scallop bed and characterize the specific acoustic signal of Iceland scallop (Chlamys islandica). A dense scallop bed was surveyed in 2002, with a QTC VIEW Series IV acoustic ground-discrimination system (AGDS) connected to a 38 kHz, 7° split-beam SIMRAD EK60 scientific echosounder. In 2003, a 50 kHz, 42° single-beam SUZUKI ES-2025 echosounder was connected to a QTC VIEW Series V AGDS. The QTC VIEW data were analysed with QTC IMPACT following the standard procedures and classified into acoustic classes. Several approaches were tested: unsupervised and supervised survey strategies directed to specific benthic communities. The SIMRAD EK60 seabed volume-backscattering strength (Sv) was submitted to a principal component analysis (PCA), before and after removal of a depth trend, and the scores on the first 10 principal components were classed by a K-means cluster analysis. The same seabed Sv data were submitted to stepwise discriminant analysis whose training data sets were defined with the ground-truth photographs using different groupings: biotope types, community types, and finally scallop-density classes. All the QTC AGDS approaches failed to reveal the scallop bed, community structures, or biotopes. The QTC classifications mimicked the bathymetry with a strong correlation of the acoustic classes with depth. The seabed Sv PCA + K-means approach presented similar depth-dependence, but, the PCA + K-means on the Sv residuals revealed the scallop bed. The discriminant analysis was the best solution for the scallop density with a general classification success rate of 75% and up to 91% for the highest density class. The Sv signature of the scallop bed is presented, and the most discriminant part of the acoustic signal is identified.

Diel patterns in the habitat utilisation of sandeels revealed using integrated acoustic surveys

Tracking the movements of sandeels in relation to their habitat will provide an improved understanding of sandeel ecology, including their interrelationships with predators and fishing activity. We examined spatial and temporal changes in the behaviour and distribution of the lesser sandeel Ammodytes marinus by integrating the acoustic ground discrimination system QTC VIEW with a Simrad EK500 fisheries scientific echosounder. QTC VIEW was used to identify acoustic changes in the properties of the seabed in the presence of buried sandeels, whilst the EK500 simultaneously recorded temporal changes in their distribution throughout the water column. Our results suggest that high densities of sandeels buried in sediment give a different acoustic signal to that of its surroundings. This integrated approach showed that sandeels had a diurnal activity pattern that was strongly, although not exclusively, associated with day length. Using this integrated survey method will enable large-scale cost-effective surveys of sandeel behaviour, distribution and abundance to be conducted.

Acoustic seabed classification of marine habitats: studies in the western coastal-shelf area of Portugal

Abstract Two single-beam, seabed-classification systems, QTC VIEW Series IV and QTC VIEW Series V, were used to identify and map biosedimentary gradients in a mid-shelf area off Western Portugal. The survey area has a moderate slope, a depth ranging from 30 to 90 m along a 3.5-km axis perpendicular to the shoreline, and is characterized by smooth sedimentary and biological gradients. Ground truth for sediment grain size and macrofaunal communities was based on grab sampling at 20 sites. The sedimentary and biological data were analysed using classification and ordination techniques. The acoustic data were analysed with qtc impact software and classified into acoustic classes. The affinity groups obtained in each data set were mapped using a Geographics Information System. All showed good agreement and identified prevailing gradients along a northwest–southeast direction. Three acoustic classes were identified, corresponding to the predominant sediment types, namely fine sand with low silt and clay content, silty, very fine sand, and mud. A close relationship with benthic communities was also verified, although less marked because benthic communities continuously change along the northwest–southeast gradient. Overall, the acoustic system coupled with ground-truthing data was able to discriminate and characterize the various benthic biotopes in the survey area.

Acoustic classification of seabed habitats using the QTC VIEW™ system

Ellingsen, K. E., Gray, J. S., and Bjornbom, E. 2002. Acoustic classification of seabedhabitats using the QTC VIEW system. – ICES Journal of Marine Science, 59:825–835.The QTC VIEW acoustic seabed classification system was used in Fraenfjorden,western Norway (62 N, 7 E), to map the spatial scales and variability of benthichabitats, and to evaluate its performance. Position and water depth were loggedcontinuously along with the acoustic data. Water depth in the survey area ranged from5 to 72 m over a spatial scale of ca. 1.5 8 km and there was considerable variation insediment characteristics at 20 ground-truth sites. Six acoustically-distinct seabed typeswere identified and the QTC system defined their spatial scales and variability.Generally, the acoustic classifications were consistent at track crossings. The classifi-cation was generally in accordance with the sediment grain size and was most likelyinfluenced by the softness of the substrate. However, these sediment characteristicscould not alone explain the diversity of acoustic classes and the classes were probablyalso related to other physical or biotic seabed characteristics. The QTC systemprovides new insights but the usefulness of the acoustic classification depends upon theamount and quality of ground-truth data, which is the key aspect when relatingacoustic class to seabed type. The acoustic system collects continuous data from largeareas relatively quickly, and defines seabeds that would be missed by traditional coreor grab point samples and will therefore be highly relevant to both geological- andbenthic-diversity studies.

측심기의 음향반사 특성을 이용한 해저퇴적물의 원격분류: 부산 수영만의 예비결과

해양의 표층퇴적물을 분류하는 일반적인 방법은 ground frothing에 의한 것으로 시료채취 정점에 국한된 자료라는 한계성을 가지고 있다. 최근에는 원격분류방법의 개발로 인하여 이러한 한계성을 극복한 연속적인 자료를 얻을 수 있도록 가능하게 되었다 본 연구에서는 해저면의 원격분류결과를 실시간 수치화된 자료로 얻을 수 있는 음향장비인 QTC View라는 기기를 이용해 부산 수영만의 표층 퇴적물을 원격분류 하였다. QTC View는 50kHz의 음향측심기와 연결하였고 측정장비의 설정환경은 조사동안 일정하게 유지하였다. Ground trothing에 의한 시료 분석결과 수영만은 slightly gravelly sand, slightly gravelly sandy mud. gravelly muddy sand, clayey sand, sandy mud, slightly gravelly muddy sand 그리고 rocky bottom의 총 7개의 퇴적물형으로 분류되었다. QTC View를 이용한 1차 원격분류결과 이들 7개 중 slightly gravelly sand, gravelly muddy sand, sandy mud 및 rocky bottom 등 4개의 퇴적물형이 구분되었으며 이는 2차 원격분류결과에서도 유사하게 분포하는 것으로 확인되었다. Ground frothing에 의한 분류자료와 원격분류 자료를 비교한 결과 퇴적물형을 구분할 때 소량성분에 의해 서로 다르게 구분된 경우는 다소 차이가 있으나 연구지역 전반에 걸친 퇴적물의 분포양상은 잘 일치하는 것으로 나타났다. 따라서 QTC View는 해저퇴적물을 원격분류하는데 유효하게 이용될 수 있을 것으로 본다. Determination of sediment type is generally based on ground truthing. This method, however, provides information only for the limited sites. Recent developments of remote classification of seafloor sediments made it possible to obtain continuous profiles of sediment types. QTC View system, which is an acoustic instrument providing digital real-time seabed classification, was used to classify seafloor sediment types in the Suyoung Bay, Pusan. QTC View was connected to 50 kHz echo sounder, All parameters of QTC View and echo sounder are uniformly kept during survey. By ground truthing, the sediments are classified into seven types, such as slightly gravelly sand, slightly gravelly sandy mud, gravelly muddy sand, clayey sand, sandy mud, slightly gravelly muddy sand, and rocky bottom. By the first remote classification using QTC View, four sediment types are clearly identified, such as slightly gravelly sand, gravelly mud, slightly gravelly muddy sand, and rocky bottom. These are similar to the result of the second survey. Also the result of remote classification matches well with that of ground truthing, but for sediment type determined by minor component. Therefore, QTC View can effectively be used for remote classification of seafloor sediments.

The effect of slope and vessel speed on the performance of a single beam acoustic seabed classification system

Although the emergence of an acoustic single beam seabed classification system appears promising as a cost-effective tool to acquire information about bottom types, some limitations of this technology with respect to vessel speed and rough terrain have been identified. To further refine this technology, we examined the QTC View system to determine if it would work in an area such as the Gulf of Alaska, which is characterized by deep water, steep slopes, heterogeneous substrate. Studies were undertaken to evaluate the operational limits with respect to vessel speed and bottom slope. Results indicate that speeds between 3 and 12 kn have no significant effect on classification performance, but bottom slopes exceeding approximately 5–8° appear to cause a complete breakdown in classification accuracy. The potential of trawl-mounted sonar systems, currently under evaluation, as a potential solution to expanded range of operation over bottom slopes is discussed.

Acoustic classification of marine habitats in coastal Newfoundland

A digital acoustic seabed classification system, QTC View (Series IV) was used in the coastal waters of Newfoundland to characterize and classify marine benthic habitats. The QTC View system was calibrated in Placentia Bay at sites identified independently during a submersible research program. Four different habitats were used for calibration of the QTC View system: mud, gravel, rock, and macroalgae on rock. These different habitats were used as a ‘‘training’’ catalogue for real-time classification of marine habitats carried out in Bonavista Bay. The classification data were based on over 2000 km of survey tracks ranging in depth from approximately 10-m to 220-m depth. Post classification analyses were carried out using data visualization techniques, simultaneously comparing the classification data in mathematical and geographic settings. Following post classification, eight different marine habitats were identified using the acoustic system: mud, loose gravel, gravel, rock, sparse algae/cobble, macroalgae, high relief/deep cobble, and wood chips. Throughout the surveyed area, rock habitat dominated, followed by sparse algae/cobble and high relief/cobble habitat types. The wood chip habitat type was identified within a small area that historically had been associated with logging in coastal Newfoundland.

The effect of slope and vessel speed on the performance of a single beam acoustic seabed classification system

Although the emergence of an acoustic single beam seabed classification system appears promising as a cost-effective tool to acquire information about bottom types, some limitations of this technology with respect to vessel speed and rough terrain have been identified. To further refine this technology, we examined the QTC View system to determine if it would work in an area such as the Gulf of Alaska, which is characterized by deep water, steep slopes, heterogeneous substrate. Studies were undertaken to evaluate the operational limits with respect to vessel speed and bottom slope. Results indicate that speeds between 3 and 12 kn have no significant effect on classification performance, but bottom slopes exceeding approximately 5–8° appear to cause a complete breakdown in classification accuracy. The potential of trawl-mounted sonar systems, currently under evaluation, as a potential solution to expanded range of operation over bottom slopes is discussed.