Raw & processed data for gravity & height measurements

Data and reports

Raw and processed data represent the basic value of gravity and height measurements. Data products of different types and formats are delivered, as listed here below. Reports describe data acquisition, processing and analysis, representing the refined knowledge and value derived from the data.

Raw & processed data

Station position

Station x,y positions based on GNSS and (offshore) underwater acoustic navigation. Offshore, this is usually provided by the ship and ROV operator.
Precise depth based on GNSS, InSar or traditional land surveying (onshore) or water pressure (offshore)
x,y,z-data are usually provided for all stations in an Excel spreadsheet.

Raw gravity

Gravity as output by the sensors. For Scintrex CG-5 or CG-6 this is gravity, tilt and temperature at 10 Hz or 6 Hz sampling. For absolute gravity it may be an average number.
Sensor tilt
Sensor temperature
Date and time
Station name – to connect with position
Metadata, dependent on type of measurement and survey
Calibration constants, from most recent calibrations

Raw pressure

Pressure proxy, for instance frequency output for Paroscientific Digiquartz sensors
Sensor temperature
Sensor tilt
Date and time
Station name – to connect with position

Raw reference pressure

Pressure proxy, for instance frequency output for Paroscientific Digiquartz
Sensor temperature
Sensor tilt
Date and time
Station name – to connect with position

Oceanographic data

From CTD probes, either launched from a ship crane or attached to the ROV:
Water temperature T(x,y,z,t)
Salinity s(x,y,z,t)

Weather data

Wave height (estimated from a weather buoy, a nearby oil platform, the ship movements or a shore station)
Air temperature
Wind (average and maximum speed, direction)
Rainfall (onshore)
Sunshine

Survey progress

Position of ship, ROV, car or instrument vs. survey time
Duration of instrument set-up and de-rigging at a site
Duration of measurements

Processed data

Best estimate of station values of gravity
Uncertainty of gravity values, with spatial dependencies
Best estimate of station values of depth
Uncertainty of depth values, with spatial dependencies

Project Reports

Final reports from a project shall describe the work in a transparent way, such that processed data and their uncertainties can be well understood. Usually the report contain chapters on:

Equipment
Data acquisition
Calibrations
Benchmark status
Reference pressures (offshore)
ROVDOG pressures (offshore)
Estimated (relative) station pressures (offshore)
Pressure-to-depth conversion and time-lapse height analysis (offshore)
Gravity data processing
Estimated (relative) station gravity
Time-lapse gravity changes
Quality control and identification of noise level and noise characteristics
Analysis of time-lapse signals