k-means core function for temporal geo data

[Pa Rö]

hallo,

i want cluster geo data (lat,long,timestamp) with k-means. now i search for
a good core function, i can not find good paper or other sources for that.
to time i multiplicate the time and the space distance:

public static double dis(GeoData input1, GeoData input2)
{
   double timeDis = Math.abs( input1.getTime() - input2.getTime() );
   double geoDis = geoDis(input1, input2); //extra function
   return timeDis*geoDis;
}

maybe someone know a good core function for clustering temporal geo data?
(need citation)