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Section 3. Archiving Marine Survey data#

3.4 Navigational Data#

In addition to positional data, navigational data relating to an ROV or vessel is often collected and again provides context for data recordings or observations.

Within the VENUS project, navigational data was acquired via an IMU (Inertial Measurement Unit). Such units record motion in a number or terms, as detailed below:

  • Pitch, roll, yaw etc.
    • Pitch
    • Roll
    • Yaw
    • Wx (Vx?)
    • Wy (Vy?)
    • Wz (Vz?)
    • Ax
    • Ay
    • Az
  • RPM (motor velocities)
  • Depth
  • Heading

Reasons for archiving

  • For the future interpretation of data e.g. seeing anomalies in the results not seen before
  • For monitoring condition and erosion of wreck sites
  • For targeting areas for future dives/fieldwork

Problems and issues

As with positional data, it is important to document any processing carried out on the original datasets.

Specialised metadata

Metadata to be recorded alongside the data itself includes: Equipment used (make and model) Equipment settings Assessment of accuracy Methodology Software used Processing carried out

Deposition and Archival File Formats

ASCII text (.txt,.dat, .xyz, etc)Published standard for ASCII Raw data, usually directly from a loggerE.G. Data logger outputs as structured ASCII text and incorporated into a database. There are well established archival procedures for databases in exporting tables as delimited ASCII text and documenting through an Entity Relationship Model (ERM) and a Data Dictionary.Suitable deposition and preservation format when stored with supporting documentation.
XML: eXtensible Markup Language (.xml)A published open standard based on ASCII. Can be used for raw or processed data and within an increasing range of technologiesXML is a general-purpose markup language geared towards facilitating the sharing of data. An XML document is said to be 'well formed' when it conforms to XML's syntactical rules. It is described as valid when it conforms to semantic rules defined in a published schema. Many XML documents use a different file extension, for example .gml.Ideal for exchange and preservation if an established schema exists.

Example data

As highlighted in the Sonar section, navigational and positional data was recorded alongside Multibeam Sonar data. Figure 10, below, is a short sample from this log.

08;10;11;12;25;22;890#$PLSM,05,703215.42,4782495.06,96.60,11/10/2008 12:25:19'421
08;10;11;12;25;22;937#$PLSM,05,703215.37,4782495.13,96.64,11/10/2008 12:25:21'921
Figure 12: Example log data accompanying sonar data collection.

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