def find_3D(index,
            header,
            max_distance,
            quality=5):
    """
    Return the list of USArray 3-D EMTF keys (for repository
    :class:`Index` *index*) that are less than *max_distance* (in km)
    from the magnetometer location specified in *header*. Only include
    *quality* or greater sites.
    """
    lat = header['geodetic_latitude']
    lon = header['geodetic_longitude']
    return index.quality_subset(min_quality=quality).by_distance(lat, lon, max_distance)