def prep(stg, ns='{http://www.topografix.com/GPX/1/1}'):
    """
    This modifies the namespace path thingy so it works. I'm a bit hazy on
    exactly what's happening here, but this works so I'm going with it for now.

    This function could probably dispensed with if I deal with the namespace
    correctly. I should read the [lxml
    documentation](http://lxml.de/tutorial.html) better and also refer to [this
    post](http://stackoverflow.com/questions/37964570/read-gpx-using-lxml-and-xpath).
    [This post](http://stackoverflow.com/questions/18071387/read-gpx-using-python-elementtree-register-namespace) seems even more on topic.
    """
    return ns + stg.replace('/', '/' + ns)
