Quality control coding: Difference between revisions

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'''[In progress]
'''


'''Quality control coding'''


We suggest to follow [http://www.oceansites.org/ Ocean Sites] for QC coding. The flagging scheme is mostly compatible with the primary level flagging recommended by [http://www.ioccp.org/images/D4standards/IOC-OceanDataStandards54-3-2013.pdf IOC].
'''Shear-probe quality-control flags'''


The Q (quality control) flags associated with shear-probe measurements are bitwise flags with boolean values which are CF compliant. More information available here: https://mplnet.gsfc.nasa.gov/about-flags


{| class=wikitable style=height:14em
Every dissipation estimate from every probe must have Q flag.
The numerical values of the Q flags are as follows:
 
{| class="wikitable"
|-
! Flag Mask
! Bit
! Flag Meaning
! Example threshold value
| Ex: True =1  / False =0
| Ex: Q value
|-
| 1
| Bit 0
| Poor figure of merit
| 1.15
| 0
| 0
|-
| 2
| Bit 1
| Large fraction of data with spikes
| 5%
| 0
| 0
|-
|-
! Flag !! Meaning !! Comment
| 4
| Bit 2
| Anomalously large disagreement between dissipation estimates from probes
| 2.772
| 1
| 4
|-
|-
| 0|| unknown || No QC was performed.
| 8
|-
| Bit 3
| 1 || good data  || All QC tests passed.
| Too many iterations of despiking routine
| 8
| 0
| 0
|-
|-
| 2 || probably good data || Data have failed one or more QC tests but visual examination suggests data is good.
| 16
|-  
| Bit 4
| 3 || potentially correctable bad data || These data are not to be used without scientific correction or re-calibration (e.g. uncertain shear sensor sensitivity).
| Insufficient variance resolved
|-
| 50%
| 4 || bad data  || Data have failed one or more tests.
| 1
|-  
| 16
| 5 || -  || Not used
|-
|-
| 32
| 6 || - || Not used
| Bit 5
|-
| manual flag to be defined by user
| 7 || nominal value  || Data were not observed but reported (e.g. instrument target depth.).
| N/A
|-  
| 0
| 8 || interpolated value || Missing data may be interpolated from neighboring data in space or time.
| 0
|-
|-
| 9 || missing value || This is a fill value
| 64
| Bit 6
| manual flag to be defined by user
| N/A
| 0
| 0
|-
| 128
| Bit 7
| manual flag to be defined by user
| N/A
| 0
| 0
|-
|
|
|
|
|
| Final Q = 20
|}
|}


Climate and Forecast Metadata Convention (CF) requires that QC flags carry attributes. In netCDF (Network Common Data Form) data files, the following information for quality control flagging should be provided for each data variable <PARAM>. <br />
<br />
<PARAM>_QC <br />
 
<PARAM>_QC:long_name = “quality flag of <PARAM>”; <br />
The Q flags are combined by their addition.
<PARAM>_QC:conventions = “OceanSITES QC Flags”; <br />
For example a Q value of 20 means that the dissipation estimated failed both dissipation ratio limit test and the resolved variance test.
<PARAM>_QC:flag_values = 0, 1, 2, 3, 4, 7, 8, 9;  <br />
A value of 255 means that all tests failed.
<PARAM>_QC:flag_meanings = “0:unknown 1:good_data 2:probably_good_data 3:potentially_correctable_bad_data 4:bad_data 7:nominal_value 8:interpolated_value 9:missing_value” <br/>
The reasons for a failure can be decoded by breaking the value of Q down to its powers of 2.
 
-----------------------------
return to [[Flow chart for shear probes]]
 
[[Category: Shear probes]]

Latest revision as of 09:18, 28 August 2023

[In progress]


Shear-probe quality-control flags

The Q (quality control) flags associated with shear-probe measurements are bitwise flags with boolean values which are CF compliant. More information available here: https://mplnet.gsfc.nasa.gov/about-flags

Every dissipation estimate from every probe must have Q flag. The numerical values of the Q flags are as follows:

Flag Mask Bit Flag Meaning Example threshold value Ex: True =1 / False =0 Ex: Q value
1 Bit 0 Poor figure of merit 1.15 0 0
2 Bit 1 Large fraction of data with spikes 5% 0 0
4 Bit 2 Anomalously large disagreement between dissipation estimates from probes 2.772 1 4
8 Bit 3 Too many iterations of despiking routine 8 0 0
16 Bit 4 Insufficient variance resolved 50% 1 16
32 Bit 5 manual flag to be defined by user N/A 0 0
64 Bit 6 manual flag to be defined by user N/A 0 0
128 Bit 7 manual flag to be defined by user N/A 0 0
Final Q = 20


The Q flags are combined by their addition. For example a Q value of 20 means that the dissipation estimated failed both dissipation ratio limit test and the resolved variance test. A value of 255 means that all tests failed. The reasons for a failure can be decoded by breaking the value of Q down to its powers of 2.

return to Flow chart for shear probes

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