Data Quality Flags 

Data Quality Flags

The data provided for a data product specific variable appears in the file in the raw form. The quality of the data is provided via the Data Quality Control Flag. This flag is a mask and represents the provider's considered opinion. Data users can apply the mask to the data or not - it is the user's choice. By taking this approach, the data provided is of greatest versatility.  

As the name suggests, data quality flags are used to let the user know the quality of a particular data variable or factors that impact on the quality of a variable. In this standard we use an integer value in the range 0 to n: 

• • 0 is reserved for future use and is not used

  • 1 is always good data. 

The values of n, what they represent and how data with that flag value should be interpreted is incorporated into files by means of the a variable that is structured as follows.

A file containing just one data quality flag will contain the variable qc_flag 

Where a  file contains more that on data quality flag variable the data quality flag named is structured as:  qc_flag_<name> 

• • qc_flag_temperature

  • qc_flag_relative_humidity

  • qc_flag_pressure

  • qc_flag_wind

  • qc_flag_radiation

  • qc_flag_precipitation

Flag values are defined such that they have the same dimensions as the variables they are associated with - in other words for every data point there is a data quality flag.

type

Definition: data type of variable 

Example: byte

dimension 

Definition: Dimensions of variable. Time is always the first followed by altitude or range when dealing with profiles. Addition dimensions are added at the end.

Example: time

                  time, index

                  time, index_range, index_angle

units 

Definition: Units of a variable’s content. 

Example: 1 

long_name 

Definition: Long descriptive name which is often used for labelling plots 

Example: Data Quality flag: Temperature

flag_values

Definition: Values the data flag can have

Example: 0b, 1b, 2b, 3b

flag_meanings

Definition: How the flag should be interpreted

Example: 

not_used

good_data 

suspect_data_unspecified_instrument_performance_issues_contact_data_originator_for_more_information

suspect_data_time_stamp_error