def slice_geo_data(ld):
    """given a list of raw record dictionaries, pull out geo data, 
    and convert to floats
    """
    float_fields = ["latitude","longitude"]
    result = []
    for rec in ld:
        newr = {}
        for field in float_fields:
            newr[field] = float(rec[field])
        result.append(newr)
    return result