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Time series flags describe the origin and the quality of the data.

Possible origins of data are:

-       Original: This entails the data value is the original value. It has not been amended by Delft-FEWS

-       Completed: This entails the original value was missing and was replaced by a non-missing value.

-       Corrected: This entails the original value was replaced with another non-missing value.

Possible Qualities are:

-       Reliable: Data is reliable and valid

-       Doubtful: The validity of the data value is uncertain

-       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
The data value is the original value retrieved from an external source and it successfully passes all validation criteria set.

1

Corrected/Reliable
The original value was removed and corrected. Correction may be through interpolation or manual editing.

2

Completed/Reliable
Original value was missing. Value has been filled in through interpolation, transformation (e.g. stage discharge) or a model.

3

Original/Doubtful
Observed value retrieved from external data source. Value is valid, but marked as suspect due to soft validation limits being exceeded.

4

Corrected/Doubtful
The original value was removed and corrected. However, the corrected value is doubtful due to validation limits.

5

Completed/Doubtful
Original value was missing. Value has been filled in as above, but resulting value is doubtful due to limits in transformation/interpolation or input value used for transformation being doubtful.

6

Missing/Unreliable
Observed value retrieved from external data source. Value is invalid due to validation limits set. Value is removed

7

Corrected/Unreliable
The original value was removed and corrected. However, corrected value is unreliable and is removed.

8

Completed/Unreliable
Original value was missing. Value has been filled in as above, but resulting value is unreliable and is removed.

9

Missing value in originally observed series. Note this is a special form of  Original/Unreliable. Missing values are automatically unreliable

 

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
  • OSC: oscillation
  • SC: secondary validation, series comparison
  • FC: secondary validation, flag comparison
  • MK: secondary validation, Mann-Kendall test
  • SVP: secondary valdidation, Flag persistency (FlagPersistencyCheck)
  • SFP: start flag persistency 
  • MAN: manual edit
  • MK: mann kendall
  • CA: Conditional aggregation

 

  • 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.
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