IQUA Robotics SoundTiles | In operation be constructed by omitting the ranges nearest to the sonar origin, for example, which contain featureless water-column backscatter and outer beam areas, where there is often less definition. “You can also toggle for minimum changes in distance or rotation between images; those are very useful in either ROV or hovering AUV data acquisitions, because those types of UUV will often hover in place for a while and then maybe travel somewhere to inspect a detail of interest that they [either the operator, autopilot or onboard AI computer] have spotted,” Hurtós notes. “This results in a non-uniform distribution of images, such as 100 in just one spot and then 100 more over the entire remainder of the survey trajectory, ultimately compromising the quality of the final mosaic. Therefore, it is advisable to filter out these images to ensure the final render is smooth and free of irregularities.” Actionable information Once the mosaic is completed and the user is presented with the map of their surveyed area, they can check for quality, and, if necessary, go back through the wizard to fine-tune the mosaic. An immediate and straightforward check involves gauging the alignment of the images to the mosaic by having the software play out all the frames in chronological order across the map (by default, the full mosaic will display in an orange colour scale, while each frame shows in a blue scale to easily distinguish them). “As the sequence of frames plays out before you, you can see if terrain features like rocks or pipes appear in the same place per frame as they do in the mosaic. That alone is a good indicator that the algorithm has resolved the imaging, positioning and registration information together well,” Hurtós says. “You can also colour-code registrations by score, so that lines linking images that didn’t register well together will take a distinctive colour, based on your selection. Zoom in on those and you can bring up an interface comparing the pair of images with any overlap showing, from which you can see what caused the low registration score.” To illustrate this case, Hurtós shows us two sonar images depicting (among other details) the same rock twice, albeit with a slight rotational offset between frames. Although inconsequential from an analytical point of view, she also demonstrates here that one can manually translate or rotate the images in the pairwise registration if doing so achieves a closer alignment. At this stage, users can annotate for features in the water column, selecting points or drawing for distances, angles or squares between objects. This way, the data product can illustrate key qualities such as offsets between pipes, lengths between cracks and so on. As well as tweaking the mosaic at the micro-scale, broader changes to image contrast, colour scale and similar factors across the mosaic can be performed to tailor the data product as the user or their own customer may wish. Once satisfied with the image, it can be exported in any of the traditional formats, such as JPG, PNG or TIFF files, as well as GEOTIFFs if positioning information allows – the mosaic can then be imported into almost any geographic information system (GIS) software. Video files depicting the procedural, frame-by-frame generation of the mosaic can be exported for customers interested in understanding the path along which the UUV carried out the survey. Future As with most software products, the developers are continually on the hunt for ways to optimise and improve it. Hurtós and her team at IQUA are working to incorporate suggestions from users all the time, although as of writing, SoundTiles is considered by both the company and its customers as a mature, finished product, with no major changes being plotted or requested in its pipeline. “The next update will bring some options for improving the illumination, and uniformity thereof, in finished mosaics, and it’s really all about just adapting the software to what users ask of us now, whether that means enhancing the UI, making the processing work faster or anything else that the industry decides makes for quality software,” Hurtós concludes. 101 Uncrewed Systems Technology | June/July 2024 Future optimisations will tailor SoundTiles to better serve UUV and USV operators, including expanding the range of forward-looking sonars compatible with the software
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