# User talk:Travelling salesman/gpx reduce

Hi

thanks for the script. Very useful I am currently working through half a gb of tracks from my bike journey. I used your code and adapted it for kml-files, since those work better with google earth. I stumbled across something I don't get (wether in the new nor the old version)

def latlonele_to_xyz(lat, lon, ele): s = sin(radians(lat)) c = cos(radians(lat)) r = ele + a * b / norm([s*a, c*b]) lon = radians(lon) return r * c * sin(lon), r * c * (-cos(lon)), r * s

shouldn't that be like the following?

lat = radians(lat) lon = radians(lon) r = "seem right" return r*sin(lat)*cos(lon), r*sin(lat)*sin(lon), r*cos(lat)

compared to yours written out:

return r*cos(lat)*sin(lon), r*cos(lat)*(-cos(lon)), r*sin(lat)

I took reference in http://de.wikipedia.org/wiki/Kugelkoordinaten#Transformation_von_Differentialen in which case lat would be omega and lon would be phi.

- Although this may be outdated...: The formula you quoted is correct for standard spherical coordinates where theta starts from the north pole. However in geographic coordinates, which I applied, the latitude is measured from the equator. --Travelling salesman (talk) 17:02, 24 May 2016 (UTC)