# Fields associated with PAAT statistics

Various parameters are used to calculate the positional accuracy of a point compared to the imagery or other data being used as a point of reference. You can adjust the calculations by changing parameters or by making points inactive. You can change the confidence level and calculation methods used to obtain the statistics. When either of these parameters is changed, the statistics for the set of points can be automatically recalculated, or the analyst can choose when to recalculate. This also happens when you uncheck a point in the table to make it inactive.

## Residuals

Fields associated with the residuals

Field name

Description

3 Sigma

A value that represents the mean residual plus three times the standard deviation. Any residual value that is greater than the three sigma threshold is considered to lie outside the valid values.

Mean

The average of all the residual values for the points digitized.

Standard Deviation

A measurement that describes the way points have been dispersed. The more widely the points have been digitized on the map, the larger this value will be.

Active vs. Total Points

The number of points that are active versus the total number of points digitized during the PAAT session.

Fields associated with residuals

## Accuracy

Fields associated with the accuracy

Field name

Description

Absolute CE

The absolute circular error (CE), or horizontal accuracy, expressed in the reporting units, based on the x- and y-values.

Relative CE

The National Geospatial-Intelligence Agency (NGA) definition of relative circular error, expressed in the reporting units. This is a measure of the consistency of horizontal error direction and magnitude of the points picked in the layer being evaluated.

RMSE

The root mean square error (RMSE). This is a statistical measurement of the variance between the residual values.

Absolute LE

The absolute linear error (LE), or vertical accuracy, of the evaluation points to the reference points based on the z-values.

Relative LE

The NGA definition of relative linear error (LE), expressed in the reporting units. This is a measure of the consistency of vertical error direction and magnitude of the points picked in the layer being evaluated.

Fields associated with accuracy

## Settings

Fields associated with the settings

Field name

Description

Reporting Units

The unit of measurement associated with the statistics. This applies to the Absolute CE, Relative CE, Absolute LE, Relative LE, RMSE, Mean, Standard Deviation, and 3 Sigma values.

Confidence Level

The statistical confidence level for the accuracy assessment. The value for this field can be 90, 95, or 99. The statistics are recalculated appropriately when this value is changed.

Calculation Method

The calculation method used for the statistics. You can use the NGA standard or United States Geological Survey (USGS) standard calculation method.

Fields associated with settings

4/19/2012