Quality flags are constructed on a philosophy of two qualifiers. The first described the origin of the data and the second the quality.
Possible origins of data are:
1. Original: This entails the data value is the original value. It has not been amended by Delft-FEWS
2. Completed: This entails the original value was missing and was replaced by a non-missing value.
3. Corrected: This entails the original value was replaced with another non-missing value.
Possible qualifiers are:
4. Reliable: Data is reliable and valid
5. Doubtful: The validity of the data value is uncertain
6. Unreliable: The data value is unreliable and cannot be used.
Following this specification, the table below gives an overview of quality flag enumerations
Table D.1 Enumeration of quality flags
Enumeration | Description |
0 | Original/Reliable |
1 | Corrected/Reliable |
2 | Completed/Reliable |
3 | Original/Doubtful |
4 | Corrected/Doubtful |
5 | Completed/Doubtful |
6 | Missing/Unreliable |
7 | Corrected/Unreliable |
8 | Completed/Unreliable |
9 | Missing value in originally observed series. Note this is a special form of both Original/Unreliable and Original/Reliable. |
Next to the flag it is also possible to get or set information why the flag is as it is through the so-called flagSource. Since version 2012.01 FEWS stores not only the quality flags, but also the source of the flag, the so-called flagSource. So the user is able to see why a certain value is validated as unreliable, eg. due to exceeding of the hard max.
The list of flagSources is:
- IMP: flag is imported
- SN: soft min.
- HN: hard min.
- SX: soft max.
- HX: hard max.
- ROR: rate of rise
- ROF: rate of fall
- SR: same reading
- TS: temporary shift
- SC: secundairy validation, series comparison
- FC: secundairy validation, flag comparison
- KT: secundairy validation, Mann-Kendall test
- MAN: manual edit
- No difference is made between historic and forecast data. This is not considered a quality flag. The data model of NFFS is constructed such that this difference is inherent to the data type definition.
- External sources may either be an actual external source, a forecasting module or a transformation. The convention in NFFS the definition of data series parameter types identifies the data source.