Data Processing Techniques

After the Canadian Hydrographic Service (CHS) has acquired raw data, such as depth soundings, sonar readings and satellite imagery, it converts the data into a format that can be processed. Data processing involves applying tide and other corrections so that all depths are referenced to an established vertical datum. Positioning and orientation information, to locate depth soundings at their correct geographic coordinates, is also reviewed. Any systematic and accidental errors must be removed before the survey results can be used for nautical charts and other products.

Fortunately, advances in computer technology have kept pace with the billions of new high-resolution depth soundings that are generated by multibeam echosounders and other hydrography equipment.

To ensure the accuracy of the resulting navigational products CHS uses several techniques, of which one, CUBE (Combined Uncertainty and Bathymetry Estimator), is able to process massive amounts of data rapidly, creating statistically accurate models of the seabed.

Example 1:

Data Processing Techniques Example 1

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Example 2:

Data Processing Techniques Example 2

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The software can then highlight the blunders that can be either quickly filtered by the software, or can be reviewed and edited by the hydrographer, depending on the specifications required for the desired product.

Example 1:

Data Processing Techniques Example 3

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Example 2:

Data Processing Techniques Example 4

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Water with fewer features (or less roughosity) requires less intervention.  Waters in confined waterways with more active seabeds require more attention and are typically processed with a more "hands-on" approach. This CUBE surface guides the hydrographer on which data to reject by showing them how statistically insignificant outliers (or blunders) are.

Advanced hydrographic data processing uses a method called navigation surface to represent gridded bathymetric surfaces. Each surface represents the best estimate of the true depth of the water at precise locations across a survey area, or grid.

Using the navigation surface approach to populate a database enables hydrographers to produce or extract a variety of information products, such as contours, selected soundings or depth areas, and information on data quality. The suitability of the source data can be verified as appropriate for a particular product. Electronic navigational charts (ENCs) created from this data can be certified as the legal source of the bathymetric information for construction of nautical charts.