Sonar installations and the interpretation of the data they collect often require a good understanding of the spatial coverage and measurements provided by different beam widths and orientations (heading, tilt and roll angles). We use ArcGIS and its 3D Analyst extension to create 3D models that help illustrate the spatial dimensions of the sampling volume and other important characteristics, e.g., the orientation of the image plane of an ARIS or DIDSON sonar. Click on the image below to start an animated view of this 3D model of an ARIS imaging sonar (with a 28° spreader lens). The different colors show three different orientations of the sonar. The transparent sphere sectors represent the total beam volume of each aim. The gridded circle sectors represent the image plane of the 96-beam array, placed along the array axes, divided into cells sized 0.25 m in range and 3 beams (0.9°) across. The solid grey plane is the trash rack at the hydro intake that is being monitored. In each of the three orientations the sonar is rolled such that the plane of its array axes is perpendicular to the plane of the trash rack.
This type of visualization is also useful for presenting the results of spatial analyses, like this example of a track density map showing the spatial distribution of observations of eels moving towards the trash rack. The data provided by imaging sonars is inherently 2-dimensional, i.e. it does not provide information on the target position in the dimension perpendicular to the plane the image is projected on. Therefore the results of this analysis can only be displayed on a plane. However, placing the plane itself along the real world position of the beam axes helps better understand the spatial relationship between what we see in the acoustic images and the real world.