gc.world-traveller.org: a utility by world-traveller.org | how to use

About

This page shows you the great circle distance between any number of points on the surface of the earth. Here are some notes on how it's built and how to use it.

Great circle distances

The shortest path between two points on the surface of a sphere is a segment of a great circle. When you fly in a plane, the route you take will be something similar to the great circle joining your departure airport to your arrival airport (although it might be quite far from it - a longer route may be more efficient, for example if it avoids the jetstream when flying west, or catches it flying east). For more details, see this explanation.

Usage

This web page plots great circle routes on a map of the Earth, and it will tell you all the distances covered. To plot a route, the most useful thing to know is the IATA code for the airports. This is a three letter code, which usually appears on reservations and boarding passes. London Heathrow, for example, is LHR. Smaller airports might only have a four-letter ICAO code. Either way, simply start typing in the input box, and matching airports will be listed.

Once you know your airport codes, then you can simply enter something like LHR-SCL (show) into the route box. You can specify multi-stop paths, such as LGW-DXB-JNB-WDH-HLE (show), and you can enter as many paths as you like, separated by either commas or newlines, for example SCL-ANF,SCL-CJC (show). Press "map!", and all your routes should appear.

Detailed information about all the routes plotted is below the map - scroll down to see it. If you click to select an individual path, the map will zoom to show it, and the details listed. Click anywhere else to zoom back to the full view and display the full list of paths. If you click on an airport marker, you'll find a link to a page of detailed information, and as well as the airports on the paths plotted, you can plot all the airports in the database using the checkbox at the bottom right.

All input is case-insensitive, and spaces are ignored. If any codes that you entered weren't recognised, you'll see an error message at the bottom of the screen.

For airports that aren't in the IATA database, or any other location on the globe, you can enter the coordinates manually. They need to be given as decimal values, followed by the compass coordinate - for example, the airstrip on Saunders Island in the Falklands is at 51.378S 60.092W (show).

You can also plot ranges. For example, if you want to see what part of the globe is within 1000 miles of Saint Helena's airport, enter 1000@HLE (show).

Maps

The maps and plots are created using google's maps API.

Distances

Distances are calculated using Vincenty's formula (T. Vincenty, 1975, Survey Review XXII, p176, using the WGS84 reference ellipsoid (more information here. The formula gives distances accurate to a few millimetres, although occasionally for nearly antipodal points, it may fail to converge. I based my code on the javascript implementation of the formula given at https://www.movable-type.co.uk/scripts/latlong-vincenty.html, which is under an MIT license.

Airports

Airport data is from the OpenFlights Airports Database, which is available under the Open Database License. The database contains 7544 locations. I have made the following small corrections which haven't yet been incorporated upstream:

My version of the database is at airports.dat and may be used under the same terms as the original. If you find any other airport errors, please report them to openflights.org.

Weather

Weather information on the airport pages is obtained from OpenWeatherMap. Icons are from the public domain tempestacons set.

Feedback

If you have any comments or suggestions, drop me a line! rw at world‐traveller.org