GIS positional error ellipse calculator

Calculate sample mean east,north and ellipse semimajor, semiminor, angle degrees with your own figures.

Your numbers

Use the units shown. Results update as you change valid inputs.

Use sample mean east,north and ellipse semimajor, semiminor, angle degrees to compare changes to your inputs. The method and limits below explain the scope.

Examples

Examples

Try the starting example

Coordinate residuals [east,north]
[[1,0],[-1,0],[0,2],[0,-2]]
Bivariate normal coverage probability
0.95
Sample mean east,north
[0,0]
Ellipse semimajor, semiminor, angle degrees
[3.99715383646,1.99857691823,90]
Horizontal RMS residual
1.581139

Try another scenario

Coordinate residuals [east,north]
[[1,0],[-1,0],[0,2],[0,-2]]
Bivariate normal coverage probability
0.9
Sample mean east,north
[0,0]
Ellipse semimajor, semiminor, angle degrees
[3.5043478465,1.75217392325,90]
Horizontal RMS residual
1.581139
Calculation method

Calculation method

Sample mean east,north

Arithmetic residual means.

Ellipse semimajor, semiminor, angle degrees

Sample covariance eigenvalues scaled by sqrt(−2ln(1−p)); normal-error assumption, not a confidence interval for the mean.

Horizontal RMS residual

sqrt(mean(east²+north²)).

Symbols and units
a
Coordinate residuals [east,north]
b
Bivariate normal coverage probability

Use the units shown. A list keeps the order in which you enter its values. The symbol ^ means “raised to the power of”.

Assumptions & limits

Assumptions & limits

  • Coordinate residuals, confidence convention. Returns Covariance ellipse and summary errors. All coefficients and observations are user supplied; results describe only the stated mathematical model. Quantities are deterministic calculations from supplied observations and assumptions; no external data is fetched. Supported limits: Finite inputs only; numeric fields bounded as labelled. Lists and JSON records are limited to 256 entries unless a stricter tool bound is stated. No automatic design approval, legal conclusion, treatment recommendation or safety certification. Bivariate normal coverage probability: minimum 1e-12, maximum 0.999999.
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