The backscatter user survey comprehensively summarized the current challenges that backscatter users experience. These challenges ranged from data storage and processing speeds, skills and expertise to acquire, process and analyze the data, a lack of software to handle specific needs for information extraction from backscatter data and processing limitations either by software or computation limitations within their organization.
2.3.1.Data storage and processing speed
Many of the users commented that one of the major challenges with backscatter data was the costs associated with the ‘acquisition storage’ and ‘backup storage’ required for the large volume of backscatter data acquired by high-resolution MBES. One of the major problems this creates for future reference is the impossibility to archive the corrected backscatter data with the sounding values. When the data are retrieved there may be a lack of understanding of the influence of the acquisition settings from the original data. It was acknowledged by some users that the changes to the NetCDF support in the mosaic data set could significantly help in overcoming this limitation. At present it was noted that current IT technology and infrastructure is not ready to handle the large data volumes of
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raw and processed data from water column backscatter and seafloor backscatter in a user- friendly manner. This severely affected processing speed and ability to perform even basic analyses on such large data sets. Although this may be seen as an institutional or funding issue rather than technological it was identified in more than 20 responses in the survey (Figure 2.13).
Challenges that the users work unit had with working with backscatter data in the past 5 years. Percentage values represent number of respondents per question
2.3.2.Skills and expertise
Another major limitation highlighted by the user survey was that backscatter utility was often hampered by contractors and processing staff not being properly trained in acquiring backscatter data and that training courses (from various companies) focus almost exclusively on bathymetric processing in their curriculum. This lack of expertise has compounding issues in the field as poor training can lead to surveyors constantly adjusting sonar settings during acquisition, which can severely affect the quality of the backscatter measurements during post-processing. Few researchers or surveyors have been properly taught to fully understand the implications of the sensitivities of backscatter data and therefore little standardization is being imposed by the survey industry, research, or other institutions in conducting MBES surveys including backscatter data. As yet no generic standard operating procedures for MBES data acquisition exists which incorporate the need to acquire good backscatter data contrarily to what has been established for bathymetry.
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2.3.3.Software and Processing
Survey responses commonly mentioned that the current evolution of software and the compatibility of data between software platforms is improving and this is assisting with the increasing use of backscatter data. The limitation regarding software was mentioned in relation to both acquisition software packages and processing software packages and that sometimes the data formats between the different platforms were not compatible in the recent past. The majority of users in the survey used the following software: Sonarscope®, QPS Fledermaus®, ArcGIS®, CARIS® and MB System. From this list only Sonarscope®, QPS Fledermaus®, CARIS® and MB System are able to provide some level of backscatter data processing while ArcGIS provides image analysis only once backscatter image has been produced by the earlier listed software tools. Amongst the four backscatter processing tools, users can apply backscatter corrections and produce mosaics (image processing) with various levels of signal processing available. One survey question asked about the variety of ways that backscatter data was used as an ancillary data source and the responses ranged from; visualization for distribution maps (image processing), analysis for boundaries (image/signal processing) and as input to sediment and habitat classification map (signal processing). There was equal utility of users relying on both image processing and signal processing to draw out information from their backscatter data.
For some users, the costs of processing software(s) both to purchase and to maintain ongoing licenses was a severe limitation to their abilities to improve backscatter processing within their industry. Some users mentioned that there was a lack of “platform independent” solutions to handle backscatter processing issues. This was identified by a number of users and an example was given that few software packages were able to quantitatively handle navigation correction. In some instance there were problems with file compatibility between the software and the sonar output files so that navigation issues could not be corrected. In many instances user responses in the questionnaire said that the software documentation for both acquisition and processing packages was very poor in relation to MBES backscatter data handling. This was noted in addition to “inappropriate or missing specifications of technical details from manufacturers”.
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Many of the questionnaire participants said that the software parameters in relation to automated MBES backscatter processing were “not properly tuned by users which resulted in less than ideal corrections being applied and therefore unsatisfactory results”. There was little confidence in the automated MBES backscatter processing algorithms provided by software companies in that the results were deemed unstable or “still in beta- testing mode” although they were commercially available. Many of the users commented on the need for “human intervention” at all stages of the automatic processing workflows where ‘adjustments’ were often required and that other steps appeared to be a ‘black box’. Many of the users noted that, although the limitations for acquiring, processing and analyzing BS data were going through a period of great transition, recent advances especially made by CARIS® and QPS Fledermaus® have made the process a little simpler especially with regard to cleaning artefacts from the data (nadir effect) and navigational uncertainties.