Quality control coding: Difference between revisions

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The numerical values of the Q flags are as follows:
The numerical values of the Q flags are as follows:


Q =
      0, if all checks pass
       1, if FOM > FOM_limit
       1, if FOM > FOM_limit
       2, if despike_fraction > despike_fraction_limit
       2, if despike_fraction > despike_fraction_limit
       4, if |log(e_max)-log(e_min)|> diss_ratio_limit X \sigma_{\ln\varepsilon}
       4, if |log(e_max)-log(e_min)|> diss_ratio_limit X \sigma_{\ln\varepsilon}
       8, if despike_iterations > despike_iterations_limit
       8, if despike_iterations > despike_iterations_limit
       16, manual flag by user
       16, if variance resolved > 50%
 
      32, manual flag defined by user
The Q flags are combined by their addition.
For example a Q value of 3 means that the dissipation estimated failed both FOM_limit test and the despike_fraction test.
A value of 15 means that all tests failed.
A failure of any one test (<math>Q\ne0</math>) means that a dissipation test should not be trusted.
The reasons for a failure can be decoded by breaking the value of Q down to its powers of 2.
 
 
'''Ocean Sites'''
Providing quality-control flags according to Ocean Sites is encouraged.
These are described at [http://www.oceansites.org/ Ocean Sites] for quailty control (QC) coding.
This flagging scheme is mostly compatible with the primary level flagging recommended by [http://www.ioccp.org/images/D4standards/IOC-OceanDataStandards54-3-2013.pdf Intergovernmental Oceanographic Commission of UNESCO (2013)].
However, only the flags of 0, 1, and 4 make sense for dissipation estimates derived from shear-probe data.




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! Meaning
! Meaning
! Comment
! Comment
|-
| 0
| unknown
| No QC was performed.
|-
|-
| 1
| 1
| good data
| if FOM > FOM_limit
| All QC tests passed.
| ?
|-
|-
| 2
| 2
| probably good data
| if despike_fraction > despike_fraction_limit
| Data have failed one or more QC tests but detailed examination after processing (e.g. by visual examination) suggests data is good.
| ?
|-
| 3
| potentially correctable bad data
| These data are not to be used without scientific correction or re-calibration (e.g. uncertain shear sensor sensitivity).
|-
|-
| 4
| 4
| bad data
| if |log(e_max)-log(e_min)|> diss_ratio_limit X \sigma_{\ln\varepsilon}
| Data have failed one or more tests.
| ?
|-
|-
| 5
| 8
| -
| if despike_iterations > despike_iterations_limit
| Not used
| ?
|-
|-
| 6
| 16
| -
| if variance resolved > 50%
| Not used
| ?
|-
|-
| 7
| 32
| nominal value
| manual flag to be defined by user
| Data were not observed but reported (e.g. instrument target depth.).
| ?
|-
| 8
| interpolated value
| Missing data may be interpolated from neighboring data in space or time.
|-
| 9
| missing value
| This is a fill value
|}
|}


<br />
<br />
[Rolf left the stuff below in place because I do not know what to do with it.]


 
The Q flags are combined by their addition.
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 />
For example a Q value of 3 means that the dissipation estimated failed both FOM_limit test and the despike_fraction test.
<br />
A value of 15 means that all tests failed.
<PARAM>_QC <br />
A failure of any one test (<math>Q\ne0</math>) means that a dissipation test should not be trusted.
<PARAM>_QC:long_name = “quality flag of <PARAM>”; <br />
The reasons for a failure can be decoded by breaking the value of Q down to its powers of 2.
<PARAM>_QC:conventions = “OceanSITES QC Flags”; <br />
<PARAM>_QC:flag_values = 0, 1, 2, 3, 4, 7, 8, 9;  <br />
<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/>




[[Category: Shear probes]]
[[Category: Shear probes]]

Revision as of 19:08, 3 June 2022

In progress


Shear-probe quality-control flags

The Q (quality control) flags associated with shear-probe measurements are not compatible with the Ocean Sites Ocean Sites for quality control (QC) coding.

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

      1, if FOM > FOM_limit
      2, if despike_fraction > despike_fraction_limit
      4, if |log(e_max)-log(e_min)|> diss_ratio_limit X \sigma_{\ln\varepsilon}
      8, if despike_iterations > despike_iterations_limit
      16, if variance resolved > 50% 
      32, manual flag defined by user


Flag Meaning Comment
1 if FOM > FOM_limit ?
2 if despike_fraction > despike_fraction_limit ?
4 log(e_max)-log(e_min)|> diss_ratio_limit X \sigma_{\ln\varepsilon} ?
8 if despike_iterations > despike_iterations_limit ?
16 if variance resolved > 50% ?
32 manual flag to be defined by user ?


The Q flags are combined by their addition. For example a Q value of 3 means that the dissipation estimated failed both FOM_limit test and the despike_fraction test. A value of 15 means that all tests failed. A failure of any one test ([math]\displaystyle{ Q\ne0 }[/math]) means that a dissipation test should not be trusted. The reasons for a failure can be decoded by breaking the value of Q down to its powers of 2.

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