VerticalAccuracy

Absolute accuracy

Line	Component	Measure Description
1	Name	absolute linear error at 90 % significance level of biased vertical data
2	Alias	LMAS
3	Data quality element	Absolute or External Positional Accuracy
4	Data quality basic measure
5	Definition	absolute vertical accuracy of the data’s coordinates, expressed in terms of linear error at 90 % probability given that a bias is present
6	Description	See STANAG 2215 ed7 Appendix 2
7	Parameter
8	Data quality value type	Measure
9	Data quality value structure
10	Source reference	NATO STANAG 2215 ed7 ISO 19157 measure n°40
11	Example
12	Identifier	http://dgiwg.org/metadata/qualityMeasure/LMAS

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Line	Component	Description
1	Name	absolute linear error at 90 % significance level of biased vertical data (Alternative 2)
2	Alias	ALE
3	Element name	absolute or external accuracy
4	Basic measure	not applicable
5	Definition	absolute vertical accuracy of the data’s coordinates, expressed in terms of linear error at 90 % probability given that a bias is present
6	Description	A comparison of the data (source) and the control (reference) is calculated in the following manner: 1. Calculate the absolute error in the vertical dimension at each point: δ V i = source V i − reference V i for i = 1 … N 2. Calculate the mean vertical error: | δ V ¯ | = | 1 N ∑ i = 1 N δ V i | 3. Calculate the standard deviation of the vertical errors: σ V = 1 N ∑ i = 1 N δ V i 2 4. Calculate the ratio of the absolute value of the mean error to the standard deviation: ratio = | δ V ¯ | / σ V 5. If ratio > 1 , 4 , then k = 1 , 2815 6. If ratio ≤ 1,4, then calculate k based on the ratio of the vertical bias to the standard deviation of the heights using a cubic polynomial fit through the tabular values as defined in the Handbook of Tables for Probability and Statistics (Reference[ 20 ]). k = 1 , 643   5 − ( 0 , 999   556 × ratio ) + ( 0 , 923   237 × ratio 2 ) − ( 0 , 282   533 × ratio 3 ) 7. Compute LE90 for the source: LE90 source = | δ V ¯ | + ( k × σ V ) 8. Compute absolute LE90: LE90 abs = LE90 reference 2 + LE90 source 2
7	Parameter	Name: Sample size Definition: minimum of 30 points is normally used but may not always be possible depending on identifiable control points. For feature level attribution sample 10 % of the feature population. Value Type: Real
8	Value type	Measure
9	Value structure	-
10	Source reference	ISO 19157 n°41 1. Mapping, Charting and Geodesy, Accuracy (Reference[ 21 ]) 2. Handbook of Tables for Probability and Statistics (Reference[ 20 ]) 3. NATO STANAG 2215 IGEO (Reference[ 22 ])
11	Example	-
12	Measure identifier	http://dgiwg.org/metadata/qualityMeasure/ALE

Relative accuracy

Line	Component	Description
1	Name	absolute linear error at 90 % significance level of biased vertical data (Alternative 2)
2	Alias	ALE
3	Element name	absolute or external accuracy
4	Basic measure	not applicable
5	Definition	absolute vertical accuracy of the data’s coordinates, expressed in terms of linear error at 90 % probability given that a bias is present
6	Description	A comparison of the data (source) and the control (reference) is calculated in the following manner: 1. Calculate the absolute error in the vertical dimension at each point: δ V i = source V i − reference V i for i = 1 … N 2. Calculate the mean vertical error: | δ V ¯ | = | 1 N ∑ i = 1 N δ V i | 3. Calculate the standard deviation of the vertical errors: σ V = 1 N ∑ i = 1 N δ V i 2 4. Calculate the ratio of the absolute value of the mean error to the standard deviation: ratio = | δ V ¯ | / σ V 5. If ratio > 1 , 4 , then k = 1 , 2815 6. If ratio ≤ 1,4, then calculate k based on the ratio of the vertical bias to the standard deviation of the heights using a cubic polynomial fit through the tabular values as defined in the Handbook of Tables for Probability and Statistics (Reference[ 20 ]). k = 1 , 643   5 − ( 0 , 999   556 × ratio ) + ( 0 , 923   237 × ratio 2 ) − ( 0 , 282   533 × ratio 3 ) 7. Compute LE90 for the source: LE90 source = | δ V ¯ | + ( k × σ V ) 8. Compute absolute LE90: LE90 abs = LE90 reference 2 + LE90 source 2
7	Parameter	Name: Sample size Definition: minimum of 30 points is normally used but may not always be possible depending on identifiable control points. For feature level attribution sample 10 % of the feature population. Value Type: Real
8	Value type	Measure
9	Value structure	-
10	Source reference	ISO 19157 n°41 1. Mapping, Charting and Geodesy, Accuracy (Reference[ 21 ]) 2. Handbook of Tables for Probability and Statistics (Reference[ 20 ]) 3. NATO STANAG 2215 IGEO (Reference[ 22 ])
11	Example	-
12	Measure identifier	http://dgiwg.org/metadata/qualityMeasure/ALE