[FIXED] How to calculate distance from a GPX file?

Issue

I have a GPX file with a GPS track. Now I want to calculate the distance I covered with this track.

What's the best way to calculate this?

Solution

The traditional way of calculating the distance between two points (each pair of waypoints in your GPX file) is with the Haversine formula.

I have a SQL Server function that implements the algorithm. This should be easy to translate into other languages:

create function dbo.udf_Haversine(@lat1 float, @long1 float, 
                   @lat2 float, @long2 float) returns float begin
    declare @dlon float, @dlat float, @rlat1 float, 
                 @rlat2 float, @rlong1 float, @rlong2 float, 
                 @a float, @c float, @R float, @d float, @DtoR float
    
    select @DtoR = 0.017453293
    select @R = 3959      -- Earth radius
    
    select 
        @rlat1 = @lat1 * @DtoR,
        @rlong1 = @long1 * @DtoR,
        @rlat2 = @lat2 * @DtoR,
        @rlong2 = @long2 * @DtoR
    
    select 
        @dlon = @rlong1 - @rlong2,
        @dlat = @rlat1 - @rlat2
    
    select @a = power(sin(@dlat/2), 2) + cos(@rlat1) * 
                     cos(@rlat2) * power(sin(@dlon/2), 2)
    select @c = 2 * atn2(sqrt(@a), sqrt(1-@a))
    select @d = @R * @c
    
    return @d 
end

This returns the distance in Miles. For kilometers, replace the earth radius with it's km equivalent.

Here is a more in-depth explanation.

Edit: This function is fast enough and accurate enough for doing radius searches with a ZIP code database. It has been doing a great job on this site for years (but it no longer does, as the link is broken now).

Answered By - cdonner

Answer Checked By - Terry (PHPFixing Volunteer)