Daily Data Quality Control
Spatial quality control.
All daily data stored in the database go through a series of controls. Three levels of control mechanism are applied in the Clidata system, as follows:
- By definition – each value is checked before it is stored into the database. The basic controls are on the existence of the definition of the station and the definition of the station observation for the observed element. Next the value is checked on lower and upper limits. These limits are optionally defined by user for each measured element. Stored values are always rounded according to user definition. If some flags are defined for the element, they are checked as well (for example we can observe the ice on the wet bulb temperature - indicated by a special flag).
- By Quality Control formula – in the Clidata system, general formula for quality control on the data can be defined. Users can define the relationship between elements. A data checking form highlights the values not satisfying the quality control formulas. The user can correct the value and assign it a quality flag. For example, we can check if the minimum temperature is less than the maximum temperature during a day. Two different types of formulas exists in the system: the warning and the error.
- Spatial Analysis – the highest level of the control is the comparison between neighbouring values. This part of the Clidata application uses ArcView (GIS) software. The colour points representing different values are displayed on the map. These points are located exactly where the stations measuring the controlled values are located. If the colour of some station is markedly different from neighbours, the user can display more detailed information about the values and may indeed correct them if necessary.
- After the series of Quality Controls data are marked as validated. The system forbids changes to validated data. Only a privileged user can remove validation flags permitting change.