Project

Bathymetry data quality

Goal: The aim of the project is the development of new visualization and integration methods of depth data quality on nautical charts to support decision making on board.

Date: 14 May 2019

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Project log

Christos Kastrisios
added a research item
Measurements of the depth of the seabed vary widely in both horizontal and vertical accuracy. To convey this information to mariners, Zones of Confidence (ZOC) are defined for charts. A mosaic of ZOCs can be represented as a chart overlay. This study evaluates two novel designs for textures to represent ZOCs. Both use textures with countable elements to represent different ZOC levels. One uses a texture made of lines where the number of lines in a texture cell represents the confidence level; the other uses dot clusters where the number of dots similarly represents the ZOC level. In the study, these were compared with three alternatives that used color to respond and accuracy as dependent variables. The dot clusters design yielded the fastest responses overall. A method using levels of color transparency proved to be the slowest and least accurate.
Christos Kastrisios
added a research item
Geospatial data may vary in quality in accuracy, precision, completeness, and consistency in space, time, and theme. Geospatial data quality allows producers to evaluate and report how well a dataset meets the criteria set forth in the product specification and users to assess fitness for use for a particular application. Working with data quality includes understanding the data quality concepts, defining data quality conformance levels in data product specifications based on product requirements, specifying quality aspects in application schemas, evaluating, and reporting. The IHO Data Quality Working Group (DQWG) provides guidance on data quality aspects to hydrographic offices to ensure harmonized implementation. In 2021 DQWG Meeting, a sub-WG was formed and tasked to perform a cross-check of the existing S-1xx Product Specifications and their respective data-quality chapters to the data quality aspects described in IHO S-97 (IHO Guidelines for Creating S-100 Product Specifications). In this work we present the results of the comparison that identified various discrepancies between the S-1xx Product Specifications and IHO S-97, as well as inconsistencies among them. Accordingly, we discuss the development of a template that aims to ensure harmonization across product specifications, and a cross-check of data quality evaluation methods.
Christos Kastrisios
added a research item
The S-57 Category of Zone of Confidence (CATZOC) symbology with star glyphs has received much criticism for its effectiveness in maritime navigation. It adds significant clutter on Electronic Chart Displays and Information System (ECDIS) screens, obscures high-quality more than low-quality data, may not be visible in small areas, is not intuitive, and dominates the screen, especially in ECDIS dusk and night modes. Consequently, the International Hydrographic Organization relevant working groups have decided that the stars symbology will not be used in S-101 and alternative methods should be investigated. This work presents the development of new coding schemes for the visualization of the six categories of the Quality of Bathymetric Data, the successor of CATZOC in S-101. We propose the use of a sequence of textures created by combining two or more visual variables. The advantage is that textures are minimally used in ECDIS displays, and, when they consist of open meshes, they minimally interfere with other chart information. Each texture is visually denser than the last, with denser textures representing greater uncertainty. The textures contain countable elements designed so that the CATZOC in a region can be determined without recourse to a legend. With the support of a user study, we demonstrate that this results in a visualization that is intuitive (thus making it easy to identify and memorize the different categories), does not obscure the underlying charted information (e.g., depths), does not alter user perception of it (e.g., shallow/ deep depth areas), and is effective in all ECDIS modes.
Christos Kastrisios
added a research item
Navigational charts contain a combination of geospatial information of varying quality collected at different times using various techniques. Bathymetric data quality is mainly encoded in electronic charts with the Category of Zones of Confidence (CATZOC). CATZOC provides information about the horizontal and vertical uncertainty of depth information, as well as the seabed coverage and feature detection. It is visualized in Electronic Chart Display and Information Systems (ECDIS) as an additional layer with glyphs using a rating system of stars: six to two stars for the best to lowest quality data and "U" for unassessed data. The current symbology creates visual clutter which is worse in areas of high quality bathymetry. Furthermore, horizontal and vertical uncertainties may not be adequately assessed by the user. This paper presents a research program aimed at the development of a method for portraying bathymetric data quality and for integrating the quantified uncertainties in ECDIS.
Christos Kastrisios
added a research item
Data quality is visualized in ECDIS as an additional layer with symbols using a rating system of stars: six to two stars for the best to lowest quality data and “U” for unassessed data. This work presents an alternative methodology for consideration by the IHO Data Quality Working Group members.
Christos Kastrisios
added a research item
Presentation of an improved method for the visualization of zones of confidence (ZOC) and quality of bathymetric data (QoBD) on ECDIS.
Christos Kastrisios
added an update
Poster presented at the 18th Symposium on Coastal Navigation, American Meteorological Society 100th Meeting, Boston, MA, USA
 
Christos Kastrisios
added a research item
Most navigational charts are an amalgamation of geospatial information of varying quality collected using different techniques at different times. Data collected with high resolution multi-beam echo sounders or lidar systems may co-exist on the chart with data collected with lead-line as far back as the 18th century. Data quality on charts is currently provided as a series of Category Zone of Confidence (CATZOC) values. For every part of the chart, CATZOC values provide information about the horizontal and vertical uncertainty of bathymetric information, as well as the seabed coverage and feature detection. CATZOC is portrayed in ECDIS as an additional layer with glyphs using a rating system of stars: six to two stars for the best to lowest quality data and “U” for unassessed data. With the provided information mariners may interpret the seabed morphology, identify shoals that pose a threat for the plotted voyage, and select routes that maintain under-keel clearance, however it is not always well understood and utilized by mariners. The aim of this research work is the development of new visualization and integration methods of data quality on charts to support decision making on board. In this two-fold work we begin with investigating new visualization methods for the bathymetric data uncertainty on charts and we subsequently utilize the results of the visualization work for the integration of marine navigation related information in support of decision making and safe navigation of ships.
Christos Kastrisios
added a project goal
The aim of the project is the development of new visualization and integration methods of depth data quality on nautical charts to support decision making on board.