Keywords : data, processing

Data processing

The extent of problems to solve around multibeam sounders data is vast (geometry, transfer function for reflectivity measurements, filtering, cartography, ...); moreover recent sounders deliver more and more dense data.

To conduct quality control tasks and to entirely exploit delivered data (bathy, reflectivity, detection mode, directivity diagrams in transmission and in reception, ...) we had to build our own tool facilitating the interactive analysis of all those data and permitting to easily implement new ideas.

The language choice imposed itself : Matlab is an interpreted language but also a "programming" language having a syntax very close to mathematic notations. It offers various mathematic and statistic functions, signal and image processing as well as graphic plans functions, image visualisation and all that is needed to realise graphic interface. It features object-orientated programming, which was used for SonarScope. Moreover, Matlab is multi-platform (Windows, Linux, ...) and a specific toolbox permits to compile applications which can then be distributed freely. Regarding the required memory space for image processing, it is possible to use a "memory mapping" feature which we encapsulated into a class mapping these images onto the hard-disk like classical Matlab variables. This allows SonarScope to manage tens to hundreds of large-sized images, downloaded and available at the same time for multilayer processing operating without taking space in memory.

SonarScope uses free softwares to :
- display large-sized images (ErMapper or ImageMagik)
- represent data in a geographique area (GMT)
- display 3D data (iVew3D)
- find data on earth (Google-Earth and Nasa-World-Wind)

Before using those functionalities, the user of SonarScope has to read the copyrights of each different software.

Generalization of the processing module to all sonars and sounders which are known by SonarScope required a generic conceptual modelling of sounders. The whole of the attributes linked to an image has been generalized too. To do it simple, when one exports an image to format ErMapper, all characteristic parameters are saved so that one can load this image into a SonarScope new session and keep going on the processing as if no interruption occurred.

Notice : SonarScope can be used to process optic images, radars or others (e.g. : LIDAR)