**FEDERATION AERONAUTIQUE INTERNATIONALE - World Distance Calculator**

**World models available: WGS84 Ellipsoid, FAI Sphere**

(operation instructions available at the end of this page)

**Operation:**

- For the calculator to operate, Javascript must be enabled.
- Read the operating instructions below and the notes at the end. Scroll the display so that all of the boxes are on screen with the Lat/Long boxes at the top and the output boxes towards the bottom of the screen. You are now ready to make calculations.
- Enter Latitude and Longitude for the points at the beginning and end of the leg to be calculated, selecting N/S and E/W as required. Enter Lat/longs in the form:
**DD.dddddd or DD:MM.mmm or DD:MM:SS.ss**, where colons separate degrees, minutes and seconds. Different styles may be used for each Lat/Long entry, entry of decimal places is not required for the calculator to operate, but all four lat/long boxes must have something entered (even a single zero). - Select desired distance units and earth model, and click on the "COMPUTE" box.
**If the calculation does not complete:**Click the "RESET" button, re-enter the lat/longs, then click "COMPUTE" again.

**Notes:**

- Conversion factors used (exact figures, by international definition): International Nautical Mile = 1852m; Statute Mile = 5280ft; 2.54cm = 1 inch = 1/12 ft.
- Above about 89 degrees latitude, and between near-antipodal (opposite) points, courses may not be accurate.

**Calculation program:** by Ed Williams. Calculations use the Vicenty Algorithm (Source: *Direct and Inverse Solutions of Geodesics on the Ellipsoid with Application of Nested Equations*, Survey Review, XXII, 176 (1975)). See also the Aviation Formulary, also by Ed Williams.

**Text:** by Ian Strachan

**Online version:** the world distance calculator can also be consulted and used online at http://www.fai.org/distance_calculation/

**FAI:** the website of Federation Aeronautique Internationale, the World Governing Body for Air Sports, can be consulted at www.fai.org