General

Ocean acoustic travel-time tomography is a remote-sensing technique for monitoring the ocean interior. Measuring the travel times of pulsed acoustic signals propagating through the water mass over a multitude of different paths, and exploiting the knowledge about how travel times are affected by the sound-speed (temperature) distribution in the water, the latter can be obtained by inversion.

Tomolab is an integrated software package, developed in the  framework of the OCTOPUS project (EU/MAST-3), for the design, processing and analysis of ocean acoustic tomography experiments. It contains toolboxes for experiment and instrument description, ocean data analysis, forward and inversion-related acoustic calculations, transceiver navigation, tomography data pre-processing, travel-time estimation, peak identification and slice inversion. 

Download

• the Demonstration of Tomolab (TOMO_DEMO.tar.gz ,   Matlab required, 5Mb)
• the User's Guide for Tomolab (Postscript 3Mb /  PDF 21Mb) 
• the Tomolab software (version 1.0).
  Tomolab comes in a distribution package consisting of four tar zipped files :
  • Tomolab sources (TOMO_SOURCES.tar.gz , Matlab required, 9Mb)
  • Reference databases (climatology, ...) (TOMO_DBASES.tar.gz, 353Mb)
  • Example problems (TOMO_EXAMPLES.tar.gz , 128Mb)
  • NetCDF version for Tomolab  (NETCDF.tar.gz , Matlab required, 3Mb)

Tomolab Toolboxes

The experiment and instrument setup toolboxes are used to define/describe the geographical and geometrical parameters and data of tomography experiments as well as the parameters and data referring to the moored instruments and their components (controllers, clocks, transducers, receiving arrays, navigators). 

The ocean data toolbox handles historical and experiment-specific oceanographic information (data bases) and provides sound-speed and bathymetry sections, mean parameters for temperature and salinity, sound-speed modes and their variances, as well as sound-speed to temperature conversion relations to be used for tomographic inversions. 

The acoustic toolboxes  (Forward acoustic and Inversion-related acoustic) are used to perform forward and  inversion-related acoustic calculations for a particular experiment and using ocean data defined/provided by the previous toolboxes  The forward calculations refer to arrival patterns, arrival times and related quantities using ray-trace and normal-mode codes. The  inversion-related calculations refer in addition to the derivatives of arrival times with respect to sound-speed modes (influence/observation matrices) for a set of background states. 

The navigation toolbox is used for the estimation of the tranceiver position using the time series of interrogation data between the transceiver and the bottom transponders. It is also used for the estimation of the clock drifts during the experiment exploiting endpoint or intermediate calibration data. 

The pre-processing toolbox contains tools to perform correlation processing and Doppler analysis of the raw tomography data. It can be further used for normalization, windowing and oversampling, as well as for navigation (mooring-motion) and clock-drift correction of the acoustic data. 

The estimation - identification toolbox addresses the problems of arrival-time estimation, peak tracking and identification in the pre-processed acoustic data, using manual and statistical methods, as well as the offset calibration problem to account for the uncertainty in the horizontal distance between source and receiver.This toolbox is used to convert the pre-processed acoustic data into travel-time data and identified peak tracks. 

Finally, the inversion toolbox is used to perform slice inversions and estimate averaged temperature distributions along particular sections. It covers a broad range of inversion methods, from traditional inversions of the identified peak tracks to simultaneous identification-inversion of the estimated arrival times (Skarsoulis and Send 2000) and matched-peak inversions (Skarsoulis 2000).