Calibration surveys are performed to allow adjustments of the survey data for parameters such as transducer error (pitch, roll and yaw), and navigation latency.
Calibration is performed by visually comparing the effects of various sensor offsets on a set of selected survey lines. This is done in Subset Editor.
Calibration is done on a set of data specifically surveyed to allow for calculation of minor sensor deviations from established parameters. By running the vessel over known sea bottom topography, at different speeds and directions, correction factors can be derived for various devices on the ship. These corrections are written to the HIPS Vessel File (HVF) and are then used for the duration of the survey mission to ensure correct processing of data.
To run a full calibration workflow:
• select surveyed test lines to use as calibration lines. (See Defining subset area for calibration.)
• create a HIPS Vessel file for this calibration line data.
• create a project for the calibration data.
• convert the raw calibration data to HIPS format. (See Import > Sensor Data.)
• apply sound velocity correction to the calibration data (if sound velocity data was recorded for the calibration data.) (See Sound Velocity Correction (using Kongsberg Library)
• load tide. (See Lock Subset Area (Subset Editor))
• Georeference the bathymetry in the calibration data lines to produce geo-referenced processed depths (See Georeference Bathymetry)
• create a surface to highlight the changes before and after calibration values are applied to the data. (See New Regular Gridded Surface)
• check calibration lines using the Attitude and Navigation Editors (if edits are made Merge must be applied again).
• edit and /or filter the lines in Swath Editor to remove large spikes and noisy data.
• use the HIPS Calibration tool in Subset Editor to determine navigation latency and transducer mounting offsets and to update the HVF Calibration
• apply Merge again to calibrated lines