min_lat = Tracepoint.minimum('latitude', :conditions => ['gpx_id = ?', trace.id])
max_lon = Tracepoint.maximum('longitude', :conditions => ['gpx_id = ?', trace.id])
min_lon = Tracepoint.minimum('longitude', :conditions => ['gpx_id = ?', trace.id])
min_lat = Tracepoint.minimum('latitude', :conditions => ['gpx_id = ?', trace.id])
max_lon = Tracepoint.maximum('longitude', :conditions => ['gpx_id = ?', trace.id])
min_lon = Tracepoint.minimum('longitude', :conditions => ['gpx_id = ?', trace.id])