QUALITY PARAMETERS (GeM+)
Section [XXX:QUALITY] (where XXX is the name of a section) (REL file)

The quality parameters indicate the degree of similarity between the values of the dataset and the real values. The parameters can be used to evaluate different quality aspects of the dataset. For example, the quality parameters can be used to evaluate the positional accuracy of the dataset, or to evaluate the thematic quality of a field in a database (or a raster, or an unstructured vector file).

For this reason the quality parameters (unlike the lineage and the process parameters) are usually a section that depends on other sections (about which they provide information). For instance, in the automatic generation of a metadata file in REL4 format from a classified raster two quality parameter sections are created:

A quality parameter may consist of different indicators and, at the same time, it may make use of different measures. The structure of these keys is as follows:

Parameter# =
Parameter#Indicator# =
Parameter#Indicator#Measure# =
Parameter#Indicator#Measure#TypeValues =
Parameter#Indicator#Measure#ResultValue =
Parameter#Indicator#Measure#ResultUnits =

The quality parameters are always displayed and modified in a common framework that displays the keys grouped by parameter, indicator and measure. The user may know which parameter, indicator and measure are displayed thanks to the values shown in the (i/n) keys where 'i' is the number of the displayed parameter/indicator/measure and 'n' is the total number of parameters/indicators/measures. To display different parameters/indicators/measures the user can move using the forward and back buttons (where there are buttons for parameters, indicators and measures).

Remember that the quality parameters apply as a whole. If a specific parameter is defined for a band or a multi-band layer, this implies that no other general parameter can be used even with a different name. If the user wishes to give the specific layer with the particular parameter all the other general parameters it is necessary to input each as a specific parameter for that layer. In the case of multi-spectral remote sensing images, for instance, it is usual for each band to have its own quality parameters.

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Name of the GeM+ entry: Parameter
Name of the REL file key: Parameter# (Quality of the reference system, of the raster or vector field,...)

Description and considerations: The name of the quality parameter.

When setting a new quality parameter ( "New" button) the names for parameters, indicators and measures defined are by default the most commonly used ones for the aspect of the dataset's quality being considered. These default values are:

* Horizontal reference system quality:

Parameter: Positional accuracy
Indicator: Relative horizontal accuracy
Measure: RMS
Type of values: F
Measurement value: (left blank)
Measurement units: the units of the horizontal reference system

* Quantitative, continuous band (field) quality:

Parameter: Accuracy (quantitative data)
Indicator: Relative accuracy
Measure: RMS
Type of values: F
Measurement value: (left blank)
Measurement units: units of the band (field)

* Ordinal or classified band (field):

Parameter: Semantic accuracy (categorical data)
Indicator: Accuracy of classification
Measure: Percentage of correctly classified entities
Type of values: Double precision real
Measurement value: (left blank)
Measurement units: %

The parameters' locational indicators (i/n) are modified automatically: the total number of parameters, n, increases by 1 and the position, i, is set to n as each new parameter is created.

To properly define a parameter it is necessary to define, at least, one indicator and one measure (as well as setting the measurement value, the type and the units).

Follows the proposal of: The CEN

Obligatory according to the CEN: Yes

Cardinality: N

Key type: C

AppliesToLayer: Yes
AppliesToSeries: Yes

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Name of the GeM+ entry:Indicator
Name of the REL file key: Parameter#Indicator# (Quality of the reference system, of the raster or vector field,...)

Description and considerations: The name of the quality indicator.

When creating a new quality indicator ("New" button), GeM+ assumes that a new indicator is required for the same quality parameter so all the fields in the dialogue box are set blank, except the quality parameter name, to allow all the necessary values to be input. The locational indicators of the indicators (i/n) are modified automatically.

To properly define an indicator at least one measure should be defined.

Follows the proposal of: The CEN

Obligatory according to the CEN: Yes

Cardinality: N

Key type: C

AppliesToLayer: Yes
AppliesToSeries: Yes

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Name of the GeM+ entry: Measure
Name of the REL file key: Parameter#Indicator#Measure# (Quality of the reference system, of the raster or vector field,...)

Description and considerations: The name of the quality measure.

When creating a new quality measure ("New" button) GeM+ assumes that a new measure is required for the same quality indicator so all the fields in the dialogue box are set blank, except the parameter name and the indicator name, to allow all the values to be input. The locational indicators of the measures (i/n) are automatically modified. By default, the measurement units are converted into the units used for the objects whose quality is being documented. For instance, if the reference system quality is being documented then the horizontal reference system units are used, or if the quality of a database field is being documented then the units of this field are the default.

To properly define a quality measure it should consist of a name, a value that is coherent with the type of values defined and units (although these may be defined as "No units" or "Unknown units").

The delete button only allows the measures to be deleted one by one. If the indicator to which the measure belongs has no further measures then it too is deleted and, similarly, if the parameter contains no further indicators it is also deleted.

Follows the proposal of: the CEN

Obligatory according to the CEN: Yes

Cardinality: N

Key type: C

AppliesToLayer: Yes
AppliesToSeries: Yes

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Name of the GeM+ entry: Type of values
Name of the REL file key: Parameter#Indicator#Measure#TypeValues (quality of the reference system, of the raster or vector field,...)

Description and considerations: The type of values used for the quality measure. It should be a subset of the types of values that a key may have, specifically: character string (C), logical (L), long integer (N) or real (F).

Follows the proposal of: the CEN

Obligatory according to the CEN: Yes

Cardinality: 1

Key type: C

AppliesToLayer:Yes
AppliesToSeries: No(Contains information about the Layer)

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Name of the GeM+ entry: Measurement value
Name of the REL file key: Parameter#Indicator#Measure#ResultValue (Quality of the reference system, of the raster or vector field,...)

Description and considerations: The measurement value is a value or a set of values of the type defined by the quality measure. This should be coherent with the previously indicated type of value. For instance, if the type of value is "long integer" then the measurement value cannot be "good").

Follows the proposal of: The CEN

Obligatory according to the CEN: Yes

Cardinality: 1

Key type: C (which may contain any measurement type: C, N, etc)

AppliesToLayer: Yes
AppliesToSeries: Yes

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Name of the GeM+ entry: Measurement units
Name of the REL file key: Parameter#Indicator#Measure#ResultUnits (quality of the reference system, of the raster or vector field,...)

Description and considerations: The units used for the quality measure. If the type of values is "character string" then it is assumed that there are "No units" (Implying writing "Parameter#Indicator#Measure#=" in the REL file). It is also possible that the units are unknown (implying writing "Parameter#Indicator#Measure#=?" in the REL file).

Follows the proposal of: The CEN

Obligatory according to the CEN: Yes

Cardinality: 1

Key type: C

AppliesToLayer: Yes
AppliesToSeries: Yes

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