1. Australian Antarctic Data Centre
2. Discover and Manage Data
3. Records
4. CEAMARC_CASO_200708030_BATHYMETRY

Description

Bathymetry data was collected using a Simrad EK60 echosounder. The sample data have been corrected for the relative locations of GPS antenna, transducers and waterline. A sound-speed value of 1500 m/s was applied when calculating depth.

The seafloor depth itself was defined firstly as the depth of the sounder-detected bottom minus 10m (contact Simrad for more information about their bottom-detection algorithm), and then modified manually where necessary to ensure that the line followed the seafloor as perceived by eye from the echogram. This is therefore a subjective process, and the true seafloor depth may vary from the perceived depth by several hundred metres in the worst cases. The greatest uncertainties are typically at greater depths, e.g. greater than 1000 m.

This seafloor depth line therefore refers to the approximate depth (not range from transducer) of the seafloor less 10 m, i.e. 10 m should be added to the 'depth' values in the *.CSV file to give the 'true' seafloor depth.

Depths greater than 5000 m are not available due to the 12 kHz data not being logged any deeper than this.

These data are preliminary and subject to change.

Bathymetry data was exported during the voyage by Belinda Ronai. Post voyage enquiries however should be directed to Toby Jarvis.

Quality

Raw data conists of 'bot', 'idx' and 'raw' files. The bot file contains information on a sounder detected bottom, the idx file is an index file and the raw file contains the ping data itself. These files are loadable/readable with SonarData Echoview software. In the process of loading raw files into Echoview 'EV' and 'evw' files are created. Setting used for processing data are preserved in the template 'Bathy_template_200708030.EV'. The Echoview software is used to export a time position series of depth data.

Exported data is in comma delimited ASCII format and files contain information about the seafloor-exclusion line created during analysis of the CEAMARC-CASO hydroacoustic data (collected with a Simrad EK60 echosounder system). This line was exported from the 12 kHz 'post-processed' echogram, generating CSV files with the following headings:

Ping_date (dd/mm/yyyy, UTC)
Ping_time (hh:mm:ss, UTC)
Ping_milliseconds (ms, UTC)
Latitude (of the ping in decimal degrees, 999 if unknown)
Longitude (of the ping in decimal degrees, 999 if unknown)
Position_status (quality of the GPS fix-interpolation at the ping time, where 1=good, 3=uncertain, 4=unknown)
Depth (of the surface-exclusion line in metres)
Line_status (certainty of the line depth, where 0=bad, 1=good, 2=unverified, 3=no line)
Ping_status (a user-specified status for each ping, ranging from 1-11)
Altitude (in m, -9999.99 if unknown - not sure what this is)
GPS_UTC_time (hh:mm:ss, -1 if unknown)

Access

These data are publicly available for download from the provided URL.

Temporal Coverages

• Start date: 2007-12-16 - Stop date: 2008-01-26

Spatial Coverages

Science Keywords

• EARTH SCIENCE > OCEANS > BATHYMETRY/SEAFLOOR TOPOGRAPHY > WATER DEPTH
• EARTH SCIENCE > OCEANS > OCEAN ACOUSTICS
• EARTH SCIENCE > OCEANS > BATHYMETRY/SEAFLOOR TOPOGRAPHY > BATHYMETRY

Use Constraints

This data set conforms to the CCBY Attribution License (http://creativecommons.org/licenses/by/4.0/).

Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=CEAMARC_CASO_200708030_BATHYMETRY when using these data.