Difference between revisions of "HorizontalAccuracy"

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== DGED ==
 
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DGED elevation datasets shall conform to the predefined thresholds for horizontal accuracy. Randomly selected datasets may be tested to assure that the random horizontal error per point and relative horizontal accuracy between points meet or exceed the thresholds detailed in Table 5 ( Geographic DGED Horizontal Accuracy Requirements) and Table 6 ( UTM DGED Horizontal Accuracy Requirements).
 
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Additionally, there is a goal that the absolute horizontal accuracy meets the values established in Tables 5 and 6 (or is better).
 
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Although it is not required to meet a threshold requirement, an absolute horizontal accuracy estimate will be reported for each data set.
 
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Table 5 – DGED Horizontal Accuracy Requirements
 
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Product name Spatial resolution Random Horizontal Error Per Point (σH – meters)
 
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Relative Horizontal Accuracy between Points (RH – meters) Goal: Absolute Horizontal Accuracy CE90 (meters) Angular (arc sec.) Linear(m)
 
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L0 30 1000 <= 50m
 
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L1 3 100 <= 50m
 
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L2 1 30 <= 23m
 
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L3 0,4 12 4,4 12,4 <= 15,0m
 
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L4b 0,15 5 1,75 5,00 <= 6,00m
 
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L4 0,12 4 1,41 4,00 <= 5,00m
 
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L5 0,06 2 0,71 2,00 <= 3,00m
 
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L6 0,03 1 0,35 1,00 <= 2,00m
 
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L7 0,015 0,5 0,18 0,50 <= 1,00m
 
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L8 0,0075 0,25 0,09 0,25 <= 0,50m
 
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L9 0,00375 0,125 0,04 0,125 <= 0,25m
 
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Horizontal Accuracy notes:
 
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1. The random horizontal error is the random circular error at point (reported at 90% confidence).
 
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2. The Relative Horizontal Accuracy (point-to-point) between points is calculated at the 90% confidence interval.
 
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3. The relative (point-to-point) horizontal accuracy is based on a distance (“D”) which is determined by the size of a standard DGED dataset at a given DGED Level. “D” is defined as the maximum radial distance between any two points in the said tile. The relative error is expected to vary as a function of distance between points, and its value ranges from R0 for points within one pointspacing to the table value for points at distance “D”.
 
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4. The absolute horizontal accuracy is a goal value, but not a requirement. Although not required to meet a threshold, the Absolute Horizontal Accuracy should be reported in the metadata and is measured at the 90% confidence interval as a CE90.
 
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5. Relative Horizontal Accuracy and random horizontal error may be difficult to assess in the coarse datasets. In these datasets, very large targets (which may not be available) would be required for such assessment. Therefore, the relative horizontal accuracy may not be evaluated for Levels 0 to 5.
 
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NOTE: These absolute horizontal accuracy values may be beyond current capabilities.
 

Revision as of 09:58, 23 April 2018

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

urn:dgiwg:metadata:dmf:1.0:qualityMeasure:CMAS


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

urn:dgiwg:metadata:dmf:1.0:qualityMeasure:RelCE90
<colgroup><col width="6.83%"> <col width="27.24%"> <col width="65.93%"> </colgroup><thead> </thead> <tbody> </tbody> 
                          <bold>Line</bold>

                          <bold>Component</bold>

                          <bold>Description</bold>
1 Name circular error at 90 % significant level
2 Alias circular map accuracy standard (CMAS)
3 Element name absolute or external accuracy
4 Basic measure CE90
5 Definition radius describing a circle, in which the true point location lies with the probability of 90 %
6 Description See <xref ref-type="sec" rid="sec_G.3.3">G.3.3</xref>
7 Parameter -
8 Value type Measure
9 Value structure -
10 Source reference -
11 Example -
12 Identifier 44
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