`General Information`

Introduction

The WHOI Multibeam Bathymetry Data Archive contains data from multibeam sonar systems operated by the Woods Hole Oceanographic Institution. WHOI operates these systems on two of its research vessels, R/V KNORR and R/V ATLANTIS. Each vessel is equipped with a SeaBeam 2100/12 MultiBeam Bathymetric Sonar System. The system on KNORR was installed in August of 1994, and put into service in November of 1995. The system on ATLANTIS was delivered with the vessel in February of 1997, and put into service in May of 1997. At present (February 2009), the archive contains data from one hundred eighteen KNORR cruises, and ninety-nine ATLANTIS cruises.

Data Collection

WHOI attempts to operate its multibeam sonar systems on all cruises, in order to facilitate the goal of mapping the earth's basins. Exceptions are made:

When operating within the restricted waters (generally, 200 nautical miles) of another country. Given sufficient lead time (eight to twelve months), arrangements can be made through WHOI to secure foreign clearances in order to operate in restricted waters.
If operation of the sonar interferes with other science operations. For example, when other sonar systems are in use, operating at similar frequencies.
When operation of the sonar interferes with other duties of the Shipboard Scientific Services Group (SSSG) Technicians.
During periods when no useful information can be obtained. For example, during periods of prolonged station-keeping.

When the sonar system is operational, multibeam swath data is collected for WHOI use only, unless previous arrangements have been made for acquiring the data. However, center beam depth data is regularly made available on-board the vessel as part of the overall ship data collection system.

Acquisition and Distribution of WHOI Multibeam Data

In order to balance the needs of the operator, scientific investigators, funding agencies, and the overall scientific community, WHOI has developed a policy with regard to multibeam data:

Prior to a cruise, if the Chief Scientist demonstrates a need for multibeam data, then the data collected will be proprietary to the Chief Scientist for a period not to exceed two years post-cruise. The demonstration of such a need is normally documented in the proposal that was funded and by a Chief Scientist's original cruise proposal, both of which should be submitted to the WHOI Marine Operations Coordinator well in advance of a cruise. Because the level of scientific interest for multibeam data is one factor that WHOI uses when allocating resources for shipboard support, interested users are strongly encouraged to demonstrate their needs to the Marine Operations Coordinator at the earliest possible opportunity.
At the end of a cruise, all data will be returned to WHOI and put into the WHOI archive. If a prior agreement has been made with the Chief Scientist, this data will not be distributed and will remain proprietary to the Chief Scientist for a period of two years. If no such arrangement has been made, then the data will be proprietary to WHOI for a period not to exceed two years. WHOI may distribute this data to interested investigators during this two year period.
After two years post-cruise, WHOI will submit all multibeam data to the National Geophysical Data Center (NGDC) for permanent archiving and public dissemination. Users wishing to access this data should contact NGDC.
No multibeam bathymetric data will be acquired within the 200-mile limit of foreign countries unless required clearances have been received. Principal investigators should contact the WHOI Marine Operations Coordinator at least eight months in advance of a cruise to arrange clearances, if needed.

Data Organization

Data in the archive is organized by cruise. For WHOI vessels, cruises are denoted with both a Voyage and Leg number. A new Voyage begins when the vessel departs from Woods Hole, and ends when it returns to Woods Hole. A new Leg begins when the vessel departs from port, and ends when it returns to port. The first Leg of a new Voyage (any cruise that departs from Woods Hole) is always Leg 1. If a leg begins and ends in Woods Hole, no leg number is assigned.

For each cruise. multibeam data is collected into files containing approximately one hour's worth of data. The file name denotes the date and time the file was created. Because multibeam sonar systems generate data at a rate proportional to the water depth, the size of the hourly files vary from one to a maximum of about six megabytes. In shallower water, a new file will be created whenever the current file size exceeds 400 pings, which can occur in less than one hour.

Costs

The cost of acquiring multibeam data and archiving the data in an appropriate manner is one part of the overall fiscal responsibility associated with operating modern oceanographic research vessels. As such, users with legitimate scientific needs for such data can receive it without any additional expense to their project during a cruise.

After a cruise, those users needing access to data can expect to be asked to contribute to the costs that might arise for retrieving the data from the WHOI archives. In general, these costs would cover personnel and supplies, and would vary depending on the level of effort and amount of data to be distributed. A limited amount of data can be made available without charge for on-line distribution.

Other Services

Aside from the dissemination of data, other services are available for those with special needs:

Processing of raw multibeam data, as generally found in the archive, into more refined data sets.
Production of bathymetric maps, 3-D images, and other visual products from multibeam and other data sources.
Consultation regarding the best use of multibeam systems and related data.

Costs for these other services are negotiated on an individual basis. For further information, please e-mail Peter Lemmond.