**ICOADS quality control indicator**
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- The `irf` variable stands for intermediate reject flag. A value of 2 indicates that the data source or report lacks suitable quality. This data is rejected from the [ship data
 selection](Workflow/data-selection) in [split_by_type.R](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/blob/master/rscripts/split_by_type.R)

- A deck priority is assigned in [`add_dck_priority.R `](https://git.noc.ac.uk/brecinosrivas/icoads.utils/-/blob/master/R/add_dck_priority.R).

    A certain priority is assign to some decks which are known to have a good quality data. The data expected to be of best quality is assigned a priority of 1, data with larger priority numbers will be flagged as the worst duplicate if reports are identified as potential matches. These priority values are based on those from [ICOADS](https://icoads.noaa.gov/e-doc/imma/R3.0-imma1.pdf).

**Met Office climatological check**
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A precision criteria on selected variables is used to perform a
climatological quality control on the data.

The precision criteria for each key variable per `dck`,
year and/or `sid` can be found in Table 5 of the [technical report](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/blob/master/docs/C3S_D311a_Lot2.dup_doc_v3.pdf).

Having a precision criteria not only preforms quality control on the data but helps to set tolerances when comparing variables from suspected duplicates.

A comparison of climatological variables allows for a match between reports in the [duplicate identification](Workflow/duplicate-indentification) procedure done by [`get_pairs.R`](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/blob/master/rscripts/get_pairs.R).

**Met Office track check**
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Several `dck` have `id`'s that indicate a logbook, sheet or other block of data that can be linked together to form ship tracks.

The linked `id`'s  are checked using the Met Office Quality Control track check (MOQC track check from [IMMA](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/wikis/How-to-install#install-dependencies-with-conda-all-platforms)) as well as for time duplicates.

Reports that fail the track check are flag as the worst duplicate. Where positions (lat, lon) are similar the best duplicate is select by `dck` priority and number of quality variables found by the climatological check. The track check is also perform in the same [`get_pairs.R`](https://git.noc.ac.uk/brecinosrivas/icoads-r-hostace/-/blob/master/rscripts/get_pairs.R) script.