Quality Flags

Overview

Every data value provided by CORIOLIX is accompanied by a set of quality flags. These flags are automatically assigned to each data value.

CORIOLIX quality flags are based on IOOS QARTOD quality control flag conventions. QARTOD is the Quality-Assurance/Quality Control of Real-Time Oceanographic Data, a set of manuals by the U.S. Integrated Ocean Observing System (IOOS). The CORIOLIX flag set includes some of the key flags defined in QARTOD, plus a few additional flags. More information about QARTOD flags is available here:
U.S. Integrated Ocean Observing System, 2020. Manual for the Use of Real-Time Oceanographic Data Quality Control Flags, Version 1.2. 24 pp. https://doi.org/10.25923/w8y6-d298


Flag Set Format

The CORIOLIX quality flag set is a string of 30 digits. Each digit in the string may take values of 0 (not applicable), 1 (pass), 2 (unknown), 3 (suspect), 4 (fail), or 9 (missing). The position of the digit within the flag set indicates which flag test it represents.

An example quality flag set might be:

21133422222222222222222222222

The above quality flag set indicates that the the Gap Test (the leftmost digit, in position 0) was unevaluated (2), the Syntax Test (the second digit) passed (1), the Gross Range Test (the third digit, in position 2) passed (1), the Global Range Test is suspect (3), the Recommended Range Test is also suspect (3), and the Sensor Status Test failed (4). All other tests were unevaluated (2).


 

Flag Values
Value    Meaning Definition
0 Not Applicable The QC test is not applicable to these data.
1 Pass Data have passed the QC test.
2 Unknown / Not Evaluated Quality was not evaluated, not available, or unknown.
3 Questionable / Suspect Data are suspect.
4 Fail Data have failed the QC test.
9 Missing Data Data are missing.

 

Flag Types

The flag position is counted from left to right with the count starting at zero.
Position    Name Definition
0 Gap Test If the most recent datapoint was measured and received within an expected time window and has the correct time stamp, yes (1), no (4). Placeholder. Not currently implemented.
1 Syntax Test If the message is structured properly, yes (1), no (4).
2 Gross Range Test If the data value is within the sensor min/max as currently defined by the sensor's operating range, yes (1), no (4).
3 Global Range Test If the data point falls within the global range of values for any time of year (1), if not (3). Due to the dynamic range of coastal waters, the fail flag (4) is never used.
4 Recommended Range Test If the data value is within the range recommended by the sensor manufacturer or scientific community, yes (1) or no (3).
5 Sensor Status Test If the sensor is currently undergoing maintenance or cleaning. Various categories exist including: in use (1), not in use (3), calibration in progress (4), maintenance in progress (4), repair in progress (4), testing in progress (4), unavailable for use (3).
6 Unused Reserved for future use.
7 Unused Reserved for future use.
8 Unused Reserved for future use.
9 Unused Reserved for future use.
10 Unused Reserved for future use.
11 Unused Reserved for future use.
12 Unused Reserved for future use.
13 Unused Reserved for future use.
14 Unused Reserved for future use.
15 Unused Reserved for future use.
16 Unused Reserved for future use.
17 Unused Reserved for future use.
18 Unused Reserved for future use.
19 Unused Reserved for future use.
20 Unused Reserved for future use.
21 Unused Reserved for future use.
22 Unused Reserved for future use.
23 Unused Reserved for future use.
24 Unused Reserved for future use.
25 Unused Reserved for future use.
26 Unused Reserved for future use.
27 Unused Reserved for future use.
28 Unused Reserved for future use.
29 Unused Reserved for future use.
 

Combined Flags

During data processing, such as temporal binning, it is sometimes necessary to combine the flags from different data points. In the case of binning, quality flags representing the binned data are a composite of all of the flags from that bin. To generate the combined flag set, the largest value found in each flag position is used.

For example:
Flag Set 1111144000022222222111100000000
Flag Set 2121122000033222222114400000000
Flag Set 3321122000033222222114400000000
Combined 321144000033222222114400000000
 
 
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