'modify the queryset q to limit to data that intersects with the
provided bbox
bbox - 4 tuple of floats representing \'southwest_lng,southwest_lat,
northeast_lng,northeast_lat\'
returns the modified query'

def filter_bbox(self, queryset, bbox):

    bbox = bbox.split(',')
    bbox = map(str, bbox)
    intersects = (~ (((Q(bbox_x0__gt=bbox[2]) | Q(bbox_x1__lt=bbox[0])) | Q(bbox_y0__gt=bbox[3])) | Q(bbox_y1__lt=bbox[1])))
    return queryset.filter(intersects)
