Statistical Summary Values

The statistical summary values display the statistics necessary to determine the vertical accuracy of the LIDAR surface used in the report. The values in the "Error" column of the Control Point List are used to produce the statistics, and points that are unchecked in the list are excluded from the statistics.

Mean Error (error_m):

The sum of the vertical errors divided by the number of errors (n).

Error Min, Max:

The minimum and maximum vertical error used in the calculation of the mean error.

Error Range:

The Error Range computed as |Xmax - Xmin| from the 'Error Min, Max' above.

Skew:

The measure of skew or symmetry in the error distribution. A skew of 0 is perfectly symmetric and estimates a normal error distribution. Skew values greater than 0.5 or less than -0.5 produce a warning that requires further investigation into the error distributions approximation of the normal error distribution.

å_iⁿ(error_i-error_m )³ ÷ [(n-1)(s³)]

where error is the vertical difference between the control and surface, and s is the standard deviation of the error distribution.

RMSE_z:

The root mean squared error for the errors.

Ö[ å_iⁿ (error_i²)/n]

ASPRS Accuracy Class:

NMAS/VMAS Accuracy_z (90% CI):

The vertical accuracy of the surface for 90% confidence level.

RMSE_z × 1.645

ASPRS/NSSDA Accuracy_z (95% CI):

The vertical accuracy of the surface for 95% confidence level.

RMSE_z × 1.96

Please use the following links to learn more about the NMAS/VMAS and ASPRS/NSSDA standards:

American Society for Photogrammetry and Remote Sensing (ASPRS)

Federal Geographic Data Committee (FGDC)

United States Geological Survey (USGS)