max_lat = Tracepoint.where(:gpx_id => id).maximum(:latitude)
min_lat = Tracepoint.where(:gpx_id => id).minimum(:latitude)
max_lon = Tracepoint.where(:gpx_id => id).maximum(:longitude)
max_lat = Tracepoint.where(:gpx_id => id).maximum(:latitude)
min_lat = Tracepoint.where(:gpx_id => id).minimum(:latitude)
max_lon = Tracepoint.where(:gpx_id => id).maximum(:longitude)