Coastal and Marine Geology Metadata and Data

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This documents InfoBank's usage of bathymetry.
  • "Bathymetry" (as used within the CMG InfoBank) is the water depth relative to sea level.
  • Depth values may be either negative or positive, but should all be understood to be negative.
  • Elevations (topography) are the corresponding terminology for above sea level and are positive.
  • For InfoBank, the specification of "bathymetry" also contains "topography."
  • Depths are almost always derived indirectly by measuring the time required for a signal to travel from a transmitter, to the bottom, and back to a receiver.
  • This travel time is then converted to a depth based on a variety of estimations of the signal speed through the water column.
  • This may vary based on salinity, temperature, etc.
  • Unless specifically stated in the file, 1500 meters per second of time for a two-way (surface-->bottom-->surface) travel-time is commonly used.

Bathymetric information occurs in the CMG InfoBank in a variety of formats, including:

scattered < Activity-ID >.3## files containing time sequential information along ship tracks.
swath extracted as files containing across-track depths (multiple depths at a given time).
gridded evenly spaced information typically derived from the above information types
vector/polygon bathymetry contours from either manual or computer interpretations of the above information types
analog physical records, usually electrostatic or photostatic rolls
metadata information about bathymetric analog paper rolls, inventory of gear, deployment of gear, operation of gear, magnetic tapes, and paper printer listings

InfoBank bathymetric scattered data file names:

<Activity-ID>.30# Raw uncorrected depths
<Activity-ID>.31# Raw travel-times
<Activity-ID>.32# Edited with two-way travel-times, uncorrected and corrected depths
<Activity-ID>.33# Edited two-way travel times and uncorrected depths
<Activity-ID>.35# R/V Farnella edited/Carter Table corrected depths

InfoBank bathymetric metadata file names:

<Activity-ID>.10khz 10 khz systems metadata
<Activity-ID>.11khz 11 khz systems metadata
<Activity-ID>.12khz 12 khz systems metadata
<Activity-ID>.200khz 200 khz systems metadata
<Activity-ID>.200khz7khz 200 khz + 7 khz systems metadata
<Activity-ID>.3dot5khz 3.5 khz systems metadata
<Activity-ID>.48khz 48 khz systems metadata
<Activity-ID>.4dot5khz 4.5 khz systems metadata
<Activity-ID>.7khz 7 khz systems metadata
<Activity-ID>.bathgrav bathymetry + gravity systems metadata
<Activity-ID>.bathgravmag bathymetry + gravity + magnetics systems metadata
<Activity-ID>.bathgravmagnav bathymetry + gravity + magnetics + navigation systems metadata
<Activity-ID>.bathgravnav bathymetry + gravity + navigation systems metadata
<Activity-ID>.bathmagnav bathymetry + magnetics + navigation systems metadata
<Activity-ID>.bathnav bathymetry + navigation systems metadata
<Activity-ID>.bathymetry bathymetry (only) systems metadata
<Activity-ID>.digitrack digitrack systems metadata
<Activity-ID>.echosounder echo sounder systems metadata
<Activity-ID>.multibeam multibeam systems metadata
<Activity-ID>.subbottomprofiler subbottom profiler systems metadata

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Page Last Modified: Mon Nov 4 03:37:26 PST 2013