Ellipsoidal to Orthometric Height Converter
Convert ellipsoidal (GPS) height to orthometric height using the geoid separation N: H = h − N.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the ellipsoidal height (from GPS/GNSS).
- Enter the geoid separation N for your location.
- Press Calculate for the orthometric height.
How it works
Orthometric height (above mean sea level) H = ellipsoidal height h − geoid separation N.
Worked example
h = 45.2 m, N = −30.5 m. H = 45.2 − (−30.5) = 75.7 m above the geoid.
Frequently asked questions
Where do I get the geoid separation N?
From a national geoid model (e.g. AusGeoid, GEOID18). GNSS gives ellipsoidal height; subtract N to get height above sea level.
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Cite this tool
Zerdly. (2026). Ellipsoidal to Orthometric Height Converter. Retrieved from https://www.zerdly.com/tools/ellipsoidal-height-to-orthometric-height-converter/
Length conversion table
How much one of each unit equals in the others — read each row as “1 [row unit] = …”. All values are exact conversions.
| 1 unit = | mm | cm | m | km | in | ft | yd | mi |
|---|---|---|---|---|---|---|---|---|
| 1 mm | 1 | 0.1 | 0.001 | 0.000001 | 0.03937 | 0.003281 | 0.001094 | 0.000001 |
| 1 cm | 10 | 1 | 0.01 | 0.00001 | 0.393701 | 0.032808 | 0.010936 | 0.000006 |
| 1 m | 1,000 | 100 | 1 | 0.001 | 39.370079 | 3.28084 | 1.093613 | 0.000621 |
| 1 km | 1,000,000 | 100,000 | 1,000 | 1 | 39,370.07874 | 3,280.839895 | 1,093.613298 | 0.621371 |
| 1 in | 25.4 | 2.54 | 0.0254 | 0.000025 | 1 | 0.083333 | 0.027778 | 0.000016 |
| 1 ft | 304.8 | 30.48 | 0.3048 | 0.000305 | 12 | 1 | 0.333333 | 0.000189 |
| 1 yd | 914.4 | 91.44 | 0.9144 | 0.000914 | 36 | 3 | 1 | 0.000568 |
| 1 mi | 1,609,344 | 160,934.4 | 1,609.344 | 1.609344 | 63,360 | 5,280 | 1,760 | 1 |
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.