Chair: Philippe Blondel
Working Group Members:
Christine Deplus
Martin Jakobsson
Marco Ligi
Takeshi Matsumoto
Kyoko Okino
William Ryan
Jordi Sorribas Cervantes
K. A. Kamesh Raju
Ron McNab
Wilhelm Weinrebe
This working group was active between 1995 and 2000 and had the goal to establish a database of multibeam bathymetry and other data for the mid-ocean ridge and back-arc basins.
1999 - Global Digital Database WG update
by Philippe Blondel, Chair
The objective of this working group is to establish a global inventory of Mid-Ocean Ridge multibeam data and to make it accessible through the web. Since the 1997 Steering Committee Meeting much work has gone into finding out who in each country has data, and what areas of the ridge the data covers. Many people have been contacted in different countries about collaborating on this project, although they have not all been officially invited to the working group. Most data will be compiled and accessible through linked national web sites. Some data will also be compiled at SOC and will be accessible at a site that will be distinct from the BRIDGE dataset site. A status of the data synthesis from each country is listed below:
Canada
Ron McNab from the Geological Survey of Canada (Atlantic) and the Chair of the Arctic Bathymetry working group of the International Arctic Science Committee (IASC) is the Canadian contact. He is ready to provide Canadian data and Arctic Ridge bathymetry data but is waiting for approval by the Canadian administration before starting full participation to the WG.
France
The French bathymetric data will be distributed as raw and processed (by individual cruises or as syntheses in some areas). The WWW site will be located at SISMER, which already archives IFREMER data. The database is divided into 7 areas, with different coordinators:
Zone 1 (Mohns Ridge) Céline Rommevaux (Paris)
Zone 2 (MAR) Pascal Gente (Brest)
Zone 3 (EPR) Yves Lagabrielle (Brest)
Zone 4 (Pac-Ant. Ridge) Anne Briais (Toulouse)
Zone 5 (Indian Ocean) Daniel Sauter (Strasbourg)
Zone 6 (Red Sea - Aden) Mathilde Cannat/Christine Deplus (Paris)
Zone 7 (Back-Arc Basins) Etienne Ruellan/Jérôme Dyment (Brest)
Germany
Wilhelm Weinrebe is the German contact. He has been compiling German data and has established a web server (http://www.geomar.de/sci_dpmt/geodyn/) which he plans to link with other institutions in Germany. Another bathymetry compilation is being organised by the German Oceanographic Centre, and a WWW server has been recently implemented (server (http://www.bsh.de/dod/Welcome.html). However, the bathymetry-related pages have been in construction since spring 1999.
Italy
Marco Ligi is managing a WWW server (http://terra.bo.cnr.it/BAT) that is being established for Antarctica data, including the Bouvet Triple Junction and Scotia Arc. Other data will eventually be archived there as well.
Japan
Data are in various institutions and there is no central mechanism for exchange. Various people have been contacted about various sets of data: Toshiya Fujiwara (JAMSTEC) about MAR data, Kensaku Tamaki (ORI, Tokyo) about SWIR data, and Kazuo Kobayashi (JAMSTEC) about back-arc basin data.
Korea
There is not yet any Korean mid-ocean ridge data, their data is all from back-arc basins.
Norway
The SeaMARC II MB and imaging data from the 1989 and 1990 cruises to the Norwegian-Greenland Sea should all be available from Kathy Crane, and were published in atlas format in 1995.
Portugal
The data collected under the MAST Programme are all stored at the Southampton Oceanography Centre and at IFREMER. Under EU rules, permission to use the data must be granted by the respective Programme Coordinators.
Russia
Russian ridge data are scattered in several institutions. It has been difficult to figure out who to contact for access to data. The Italians have a lot of data that were collected in collaboration with the Russians. Bob Tyce at URI (USA) supposedly synthesized some Russian MB data from the MAR. Jeff Fox would know for sure. However this might be the same data that K. Crane synthesized?
Spain
After some discussion, the Spanish representative to the WG is now Jordi Sorribas (CSIC-Barcelona). He was contacted directly at the IEEE Oceans'98 in Nice (late 1998), and given the relevant IR and BRIDGE literature. Bathymetric information is available at http://hesperides-bd.icm.csic.es/Hesperides/campanyas/lista_campanyas.htm. This site contains a list of all cruises done with the Hesperides, the kind of data, contacts and scientific results, along with bibliography and some maps. This site is constantly updated. JuanJo Dañobeita has some data from the tip of the EPR and would be happy to supply this data.
UK
Philippe Blondel is the UK contact. The BRIDGE Programme is ending soon. The BRIDGE Database is underway, and data processing is continuing until end 1999. A WWW server has been established at http://www.soc.soton.ac.uk/BRIDGE, in March 1999. It presents the data that will be released in late 2000, 2001. Some of this data can already be accessed if the PIs concerned grant their express permission. This data will be available at cost for academics. The question of database management after the end of BRIDGE has not been resolved.
USA
US RIDGE bathymetry from mid-ocean ridges is currently stored at at http://imager.ldeo.columbia.edu. The WWW server does not seem to evolve (lack of manpower and/or funding ?). WHOI has also established a server with some multibeam bathymetry (at http://mbdata.whoi.edu/mbdata.html).
Sweden/Arctic Ridges
Martin Jakobsson from the University of Stockholm is the Swedish contact and will ftp Arctic Ridge data after the Expo98.
1997 - Global Digital Database WG update
Reprinted from InterRidge News 6.1 (April 1997)
Low-resolution global topography (ETOPO5 database, 5' resolution)
1. Introduction
Knowledge of the Earth and its environment are proving increasingly crucial, and not only for scientific reasons. Information about the Earth's topography is of interest not only to geoscientists, but also to physical oceanographers (to constrain ocean circulation models), marine chemists (to assess the distribution of chemical products, harmful or not, in the deep ocean), governments (extensions of the Exclusive Economic Zones), and industries (e.g. cable or pipe-line companies). However, two thirds of the planet are covered by oceans which prevent a direct access to its topography. It has become a cliché to say that more is known about planets at the other end of the Solar System than about the Earth. It is nonetheless true, for example the whole of Venus has been mapped with a ground resolution of 100 m or less. The Earth is only slightly larger, but the best bathymetric compilations exhibit resolutions of 5 minutes of a degree, or slightly less. The establishing of a Global Ridge Bathymetry Database is therefore primordial, and the present article aims at showing the efforts of InterRidge. This article is not a consensus of all voices inside the InterRidge community. Instead, it shows the problems to address, the achievements from the national programmes that compose InterRidge and the possible way forward. From there it can lead to discussions inside InterRidge and the constituting national programs.
2. InterRidge and the National Initiatives
InterRidge is designed to encourage scientific and logistical coordination, with particular focus on problems that cannot be addressed as efficiently by nations acting alone or in limited partnerships. Its activities range from dissemination of information on existing, single-institution experiments to initiation of fully multi-national projects. A particular domain of interest is the acquisition of a balanced set of global-scale data on the entire mid-ocean ridge system. More than 50,000 km of ridges girdle the Earth where lithospheric plates move apart and new crust is formed. They are the most dynamically active places on the Earth's surface, and concentrate most of the world's volcanic activity and a large part of the seismicity in zones only a few kilometres wide. Scientific surveys have been conducted by all member countries of InterRidge, in collaboration or in the framework of their national programmes (such as BRIDGE for the UK, De-Ridge for Germany or Dorsales for France). They have produced huge amounts of bathymetric data (several Terabytes). Each country, or, more appropriately, each institution has different ways of handling and distributing the resulting datasets. It was felt that now was the time to synthesise these processes and regroup bathymetry data into one single dataset available to the whole scientific community.
3. Bathymetry Data Processing
Sonar systems providing bathymetry can be roughly divided into echosounders (one single beam oriented vertically), multibeam (several beams on each side of the ship) and sidescan sonars (one beam on each side) (e.g. deMoustier, 1988; Kleinrock, 1992; Blondel and Murton, 1997). These systems can be hull-mounted, shallow-towed, or deep-towed. Bathymetry data is supplemented by navigation and attitude information. Navigation contains the ship's position, along with its heading, speed and acceleration. Attitude data generally contains roll, pitch and yaw (and, in the case of deep-tow systems, tow-altitude, platform heading and reference net position). Navigation indicates where the sonar is, and attitude indicates where the sonar looks. Both are important, and in this article, the reference to bathymetry implicitly includes navigation and attitude as well. Depending on the origin of the bathymetry (point values for echo-sounders or series of individual measurements for multibeam and sidescan sonars), different operations will need to be performed. Pre-processing prepares the data for processing and includes cleaning the navigation and attitude files, and, if necessary, changing headers and formats. Processing per se is the transformation of raw bathymetry into usable images, or grids, that are topographically and geometrically correct representations of the seafloor. This process usually involves the detection and filtering of spurious values, and the gridding, interpolation and contouring of individual {x; y; z} values. Post-processing includes grid interpolations, mosaicking, cosmetic operations (e.g. contrast enhancement, shading), statistics and detailed image analyses (e.g. feature extraction). All these steps need to be documented as precisely as possible in order to check their accuracy, and, if new algorithms are available, to improve them. The amount of ground resolution of the final dataset depends on the final objectives. Geophysical surveys tend to stay as close as possible to the maximum resolution (generally 100 metres). Other surveys may be more interested in large-scale mapping, or only in the dangers to surfaceards have been set by well-known institutions such as IHO (International Hydro-graphic Office) or GEBCO (GEneral Bathymetric Charts of the Oceans). Although not formally set as standards, stricter rules for checking the accuracy of bathymetric measurements have also been introduced by individual scientists inside the InterRidge community.
4. Archiving and Distributing Bathymetry Products
Archiving of Bathymetry Data
Archiving of processed data is one of the problems. It is often difficult for a scientist to access the bathymetry needed for a particular project, or to even know whereto find it and how to obtain it. For example, bathymetry has been collected in the Northern portions of the Mid-Atlantic Ridge by several institutions, and some portions of the resulting datasets are stored in half a dozen institutions scattered among 4 countries. The project initiated by InterRidge of a "Global Ridge Bathymetry Database" would present the obvious advantage of regrouping the bathymetry available on mid-ocean ridges and back-arc areas in one single dataset, simplifying their access and saving time and energy.
Another problem is the format of the bathymetry data. Following recent meetings (e.g. Stewart, 1990; Blondel and Parson, 1994; 1995), and the growing concern of end-users, some de facto standards have emerged and have been gradually accepted. Text dissemination is more and more achieved through Word-RTF and TeX formats. Graphics files are easily exchanged with PostScript and a set of specific rasterfile formats (e.g. JPEG, GIF, TIFF). Many easily accessible, public domain software exist for translation between these formats. However, the choice of a common format for acoustic data is much more difficult to attain, as often it is specifically adapted to the sonar system in use, and to the processing computer. A new format, called HDF (Hierarchical Data Format), and its offspring NetCDF are architecture-independent and data-independent. They have been used in several successful bathymetry processing software such as MB (e.g. Caress et al., 1996) and GMT (Wessel and Smith, 1991). The main concern for sonar users is that the archived data format be self-describing (Blondel and Parson, 1995). This does not preclude the use of the NetCDF data format, but its use is neither necessary nor sufficient for the data to be self-describing.
Copyrights/Licences
Once an archiving methodology has been defined, the dissemination of the data must be considered. Who can provide data to the central archive? How should the data be distributed? And, concomitantly, to whom? Proprietary rights have always been considered important by scientists. The "gentlemen's agreement" system, along which use of acoustic data is freely granted as far as the proper references and acknowledgements are made, has prevailed for a long time. But the origins and extent of funding for bathymetric surveys have dramatically changed in the last years. In particular, joint ventures with private companies or associations between several countries (e.g. through the European Community) have become quite common. Funding bodies have different copyright rules, allowing different access at different costs. Furthermore, not one person or laboratory can be pinpointed as owner of the data, and new rules have to be established. The same questions arise with licensing. What are the limits in which the data can be used, reproduced, printed, re-distributed, etc.? Is the simple reference of the origin of the map sufficient, or should specific distribution fees be established? Following common business practices, it would be worth introducing formal agreements binding the two parties, somewhat like software agreements.
Physical/Electronic Distribution
The traditional way of distributing bathymetry data was by the large-scale production of maps, which were physically mailed to the end-users. Because of the high amount of data involved, and to better match the customers' requirements, leading institutions now provide bathymetric data on tapes (e.g. United States Geological Survey), on CD-ROMs (e.g. GEBCO) or print tailor-made maps in small quantities (e.g. Geological Survey of Canada). Electronic distribution has accelerated the process, by allowing on-line access to maps or portions of maps through the Internet (ftp or World-Wide Web).
A successful way of blending these different approaches has been demonstrated by a pilot study, US RIDGE Multibeam Synthesis. Bathymetric data acquired at mid-ocean ridges with funding of the US National Science Foundation is regrouped at the host site (Lamont-Doherty Geological Observatory). Its accuracy is checked, and in some cases the data is reprocessed. The raw and processed data are accessible the on-line via the World-Wide Web and on a series of CD-ROMs. Services for map generation and map printing are also offered on a cost-reimbursable fee structure. The current database covers portions of the Mid-Atlantic, Pacific and Antarctic regions.
Possible extent of the InterRidge "Global Ridge Bathymetry Database", superimposed in white over ETOPO5 topography.
Proposed coverage of the Global Ridge Bathymetry Database
5. Toward a Global Ridge Bathymetry Database
InterRidge has taken the formal decision to compile the bathymetric datasets of mid-ocean ridges (and possibly back-arc areas) produced within current national initiatives into one single database. The aim is to make high-resolution bathymetry more accessible to the world's scientific community and maximise the scientific return and to share the burden of distribution and archiving. Another expected return of this project will be the dissemination of bathymetric products to other groups than the mid-ocean ridge community (e.g. physical oceanography, satellite altimetry).
The problems to address are numerous, and are being discussed inside the InterRidge community. First, a global inventory of all bathymetric data acquired so far in the whole world needs to be made. Second, consultation of data providers and data users should clear the uncertainties related to copyright and licensing by establishing unambiguous "rules of the road". The actual compilation of the global database is the most difficult part. Where will it be hosted? Could different sites be responsible for different parts of the project? If the choice of one single site proves too unwieldy, it would be possible to have one major site acting as front-end and customer-interface for distributed sites each responsible for a different region. How would the quality control be performed? Data dissemination could easily model the RIDGE Multibeam Synthesis, with on-line access via Internet and physical distribution via CD-ROMs and tailor-made maps. One large question is how this work would be funded: national agencies or international cooperation? The final establishment of a "Global Ridge Bathymetry Database" is still a distant goal. But it is not that far. Important groundwork has been made by several national programmes. This project also benefits from the experience accumulated by other international programmes, such as SCOR, GEBCO or IHO. Bringing together the strength and motivation of scientists everywhere, InterRidge is ideally placed for this task. Scheduled for the end of the millennium, the "Global Ridge Bathymetry Database" will be a perfect summary of the advances in the knowledge of our planet which started only a quarter of a century ago.
Acknowledgements
Some of the ideas expressed in this article were brought forward, discussed and refined during a BRIDGE Workshop about "Sonar Processing in the UK" held at the Institute of Oceanographic Sciences (UK) in June 1994. They were updated through discussions with various colleagues from the InterRidge Community.
References
Blondel, Ph. and L.M. Parson, Sonar Processing in the U.K.: A short review of existing potential and new developments for the BRIDGE Community, 27 pp., BRIDGE Position Paper n. 1, May 1994.
Blondel, Ph. and L.M. Parson, Sonar Processing in the UK, 14 pp., BRIDGE Report n. 5, Jan. 1995.
Blondel, Ph. and B.J. Murton, Handbook of Seafloor Sonar Imagery, 317 pp., Wiley-Praxis, 1997.
Caress, D.W., S.E. Spitzak and D.N. Chayes, Software for multibeam sonars, Sea Technology, Vol. 37(5), p. 54-57, 1996.
Kleinrock, M.C., Capabilities of some systems used to survey the deep-sea floor, CRC Handbook of Geophysical Exploration at Sea, Hard Minerals, p 36-90, R.A. Geyer ed. CRC Press, Boca Raton, 1992.
de Moustier, C., State of the art in swath bathymetry survey systems. Int. Hydr. Rev., vol. 65( 2), p. 25-54, 1988.
Somers, M.L., Sonar imaging of the seabed, p. 355-369, in Acoustic Signal Processing for Ocean Exploration, Moura and Lourtie eds., NATO ASI Series C, vol. 388, 674 pp, Kluwer Academic, 1993.
Stewart, W.K.S., Subsea Data Processing Standards, RIDGE Workshop Report, 1990.
Wessel, P. and W.H.F. Smith, Free software helps map and display data, EOS Trans. AGU, 72, 441, 445-446, 1991.
