## Great circle calculator

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Great circle calculator

*
See also* -
Great circles

**What is the**

The

*Great circle calculator*?*Great circle calculator*is a program written in Mircosoft Excel, that, when given two locations in the world, will plot calculate the length of the great circle connecting them, and plot this great circle on a world map.

great_circle_calculator.xls | |

File Size: | 266 kb |

File Type: | xls |

(Version 1.00, 283 KB)

Below is a screenshot from the program...

**You enter two locations, either by choosing from the list of preset locations* or by inputting your own using latitude and longitude coordinates. The**

What does the

What does the

*Great circle calculator*do?*Great circle calculator*will then....- Calculate the length and path of the great circle connecting the two locations
- Plot the great circle on a world map
- Calculate the length of the line going through the Earth that connects the two locations
- Calculate how long it would take to cover the distance of the great circle and line through the Earth at a speed you choose

Below is a screenshot from the program...

**How does the**

The program uses the basic law of sperical trigonometry, which, when given the latitude and longitude of two locations, can find the angle (and hence the distance) between them. For more on this, I'd suggest reading my page on great circles.

*Great circle calculator*work?**Where did you get the information to write the**

I first came across the spherical trigonometry law in Jean Meeus' book

*Great circle calculator*?*Astronomical Algorithms*, but the law is widely known, and is easily found online (for example, see mathworld).

*Preset locations currently only include national capitals, although I am working to expand the list.