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Data Quality Report
Ruth Lawless, January 2002
Data Currency Voyage Description Logging System Data Sampling Interval
Data Gaps Software Data Quality
Data Start Time: 09 January 1992 06:55 UTC
Underway Data End Time: 26 March 1992 23:59 UTC
This was a marine science voyage. Technical support personnel were provided on board, but underway data were quality checked well post-voyage (January 2002).
|23 January - 13 February||Marine Science in vicinity of Heard Island|
|13 February - 06 March||Marine Science|
|10 - 11 March||Davis|
|15 March||Heard Island|
DLS data types were logged.
4. Data Sampling Interval: 60 seconds
5. Data Gaps
Underway data were quality checked using Java based software created by Gordon Keith and Peter Wiley. Depth data were already processed, but it is not documented when, how and by whom this was done.
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7. Data Quality
of Checked Parameters
The following is a description of what criteria were used to flag data as "good" or "bad". Underway data users should also refer to the section on Data Gaps.
Bathymetry (Water Depth)
There is no documentation relating to the processing protocol or quality of these data.
Ship’s Heading (SH)
SH is a measurement of the direction that the bow of the ship is facing.
These data were accepted as good.
Ship’s Speed (SS)
Ship's Speed data are derived from the electromagnetic current meter output (Ship's Log). SS is a measurement of ship's speed through the water and is directly affected by waves.
Ship's Speed data are believable with respect to the ship's schedule and capability and have therefore been left as good.
Fluorometer Flow (FLU_FLOW) and Fluorometer
Apart from values < 0, FLU_FLOW are all believable and were left as good.
FLU_VALUE data were rejected were flow is low or erratic. Values < 0 were marked bad. Outliers were accepted as real.
According to the programmer's log, the fluorometer was cleaned and calibrated on:
TSG_CNDUCT data points were allocated good or bad quality flags to match those of corresponding TSG_SALIN data points.
TSG_TEMP data are not an accurate measure of sea water temperature and were rejected as a matter of routine.
Water Temperature - low resolution (W_TEMP)
The accuracy of these data is inherently suspect due to the position of the temperature probe. The sensor was located about a metre within the uncontaminated seawater intake relatively high on the hull and was subject to freezing when in pack ice and taking in air during heavy pitching.
W_TEMP data were rejected where USW flow (i.e. FLU_FLOW) is low or erratic. Sections of particularly variable data and outliers were also marked bad. Although the remainder of W_TEMP data were left as good, users should acknowledge their limitations.
Air Temperature Port and Starboard (A_TEMP_P
Warm air from the exhaust funnel aft of the air temperature sensors corrupts air temperature data when upwind of them. As apparent wind direction data for this voyage are not loaded onto the marine database, it could not be determined when this occurred.
Therefore, data from both air temperature sensors were marked bad where they differ by more than about 1.0º C or where the shapes of the traces don't correlate well. Outliers and scattered data were also rejected.
Barometric Pressure (BAR)
BAR data were all accepted as good.
Humidity Port and Starboard (HUMID_P and
The humidity sensors are located close to the air temperature sensors and humidity data are therefore also affected by exhaust air from the funnel, although to a lesser extent. When a sensor is downwind of the funnel, humidity data are sometimes decreased relative to the unaffected sensor. However, as with air temperature data, humidity data could not be quality checked with respect to apparent wind direction.
Data logged from the starboard sensor is faulty and were all marked bad. As a consequence, data from the port sensor were all left as good, except for extreme outliers.
Photosynthetically Active Radiation (LICOR_R)
Note that this sensor is affected at times by shadows from the ship's superstructure.
Night-time values are slightly greater than zero, but these were left as good. Data between 23 January 06:08 UTC and 26 January 03:29 UTC were rejected as values remain constant during this period. Extreme outliers were also marked bad.
Wind Direction True Port (WDPT) and Wind
Speed True (WSPT)
Sections of the WDPT and WSPT traces do not resemble real data and were rejected. These periods coincide with electronic maintenance as recorded in the programmer's log. Outliers were also marked bad.
Apparent wind direction and wind speed data should exist, but have not as yet been loaded onto the marine database.
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