Difference between revisions of "HorizontalAccuracy"

Line

Component

Measure Description

1

Name

absolute circular error at 90 % significance level of biased data

2

Alias

CMAS

3

Data quality element

Absolute or External Positional Accuracy

4

Data quality basic measure

5

Definition

absolute horizontal accuracy of the data’s coordinates, expressed in terms of circular 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

ISO 19157 measure n°48

11

Example

12

Identifier

http://dgiwg.org/metadata/qualityMeasure/CMAS

Line

Component

Measure Description

1

Name

absolute circular error at 90 % significance level of biased data

2

Alias

ACE

3

Element name

absolute or external accuracy

4

Basic measure

not applicable

5

Definition

absolute horizontal accuracy of the data’s coordinates, expressed in terms of circular 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 horizontal dimension at each point:

Δ H i = ( source X i − reference X i ) 2 + ( source Y i − reference Y i ) 2 for i = 1…N

2. Calculate the mean horizontal error:

μ H = ( ∑ Δ H i ) N

3. Calculate the standard deviation of the horizontal errors:

σ H = ∑ ( Δ H i − μ H ) 2 ( N − 1 )

4. Calculate the ratio of the absolute value of the mean error to the standard deviation:

ratio = | μ H | / σ H

5. If ratio > 1 , 4 , then k = 1 , 281   5

6. If ratio ≤ 1,4, then calculate k, the ratio of the mean to the standard deviation, using a cubic polynomial fit through the tabular values as defined in the CRC Handbook of Tables for Probability and Statistics [ 20 ]

k = 1 , 643   5 − ( 0 , 999   556 × ratio ) + ( 0 , 923   237 × ratio 2 ) − ( 0 , 282   533 × ratio 3 )

7. Compute CE90 for the source:

CE90 source = | μ H | + ( k × σ H )

8. Compute absolute CE90:

CE90 abs = CE90 reference 2 + CE90 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 Measure n° 49

1. Mapping, Charting and Geodesy Accuracy (Reference[ 21 ])

2. Handbook of Tables for Probability and Statistics (Reference[ 20 ])

11

Example

-

12

Identifier

http://dgiwg.org/metadata/qualityMeasure/ACE

Line

Component

Measure Description

1

Name

Point-to-point horizontal accuracy

2

Alias

RelCE90

3

Data quality element

Relative or internal accuracy

4

Data quality basic measure

5

Definition

Uncertainty in the difference in horizontal positions between any 2 points. The value is expressed as a circular error at the 90% confidence level.

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

11

Example

12

Identifier

http://dgiwg.org/metadata/qualityMeasure/RelCE90