Monterey Bay Aquarium Research Institute
Data processing

The raw sonar and navigation data must be processed before maps can be made

The multibeam processing package MB-System is used extensively for planning the surveys, and for correcting roll and pitch biases, editing the sonar data, and adjusting the navigation data, post-survey.

After the AUV mission, the multibeam processing package MB-system processes the various sonar instruments' data. Processing the data involves correcting for pitch and roll errors, navigation adjustment, and editing erroneous soundings from bathymetry data. 1

It is important to adjust for navigation since the AUV accumulates many errors when using the inertial navigation system data. For a 17.5 hour mission, the upper limit on navigation error is 44 meters with a standard deviation of 10 to 20 meter errors. The MBnavadjust tool can correct navigation errors by correlating overlapping seafloor features. 1

The sidescan data is processed by using the multibeam bathymetry instead of using a flat surface. The subbottom profiler data can be processed using MB-System. Various data products from the sensors can be used to produce grids, mosaics, and maps. 1

Planning the survey

Surveys are planned with MB-System's package "Mbgrdviz". Altitude off the bottom, line spacing, and crossings can all be specified. Missions are typically composed of a sequence of straight lines that connect at waypoints. Missions are downloaded to the vehicle over a radio link before the dive. Waypoints can also be sent to the ship's bridge.
survey plan
Plan to "mow the lawn" (survey grid) in Mbgrdviz.
© MBARI 2005

Roll and pitch bias correction

The vehicle's roll and pitch are logged and can be accounted for in post-processing.

Editing sonar data

Sonar data are edited with MB-System's package "mbedit". All the beams within each ping of the swath are displayed for editing. Bad beams can be flagged so that they will not be considered during further processing.

Screen grab of mbedit in use.
© MBARI 2005

Navigation adjustment

Programmed into the deployment's track are several crossings so that drift during the dive can be corrected later. MB-System's utility "Mbnavadjust" is used to match features in overlapping swaths and adjust the navigation.

>> More about the vehicle navigation

nav adjustment
Screen grabs of Mbnavadjust showing procedure to obtain best fit of overlapping swaths.
© MBARI 2005
References: 1 Paduan, J.B., Caress, D.W., Clague, D.A., Paull, C.K., Thomas, H., “High-Resolution mapping of mass wasting, tectonic, and volcanic hazards using the MBARI Mapping AUV”, International conference on seafloor mapping for geohazard assessment, Forio d’Ischia, Italy, May 11-13, 2009.