GeoNames Forum

Hi,
I have one problem in my work, in my work there is a need to find the near by places according to the given distance of a place. for example if we provide the geoname id of a place we have to display the all near by geoname ids acording to the given distance like 25 miles.

and what is "great circle distance".

Any one can please help in this regard.

I found a very easy formula on the Dr Math forum.

http://www.mathforum.com/library/drmath/view/51711.html

I have used it to find the nearest weather station to a user entered lat/long and it works fine.
Hopefully is will be of use to you.

I have found a much more substantial approach to distance.

Method 1
Great circle method. Assume that the earth is a perfect sphere and apply the spherical trigonometry equation. (see Dr Math)

Method 2
Vincenty’s formula. This is the most accurate and widely used globally-applicable model for the earth ellipsoid.

The full explanation of Method 2 and JavaScript code can be found at
www.movable-type.co.uk/scripts/latlong-vincenty.html