In 1998, the DMC began using location identifiers to uniquely identify a data stream among many data streams for the same channel ID and station ID.
EXAMPLE: ANMO.IU.00.BHZ.xxxx and ANMO.IU.10.BHZ.xxxx means there are two different instruments (00 and 10) at the ANMO site that use the BHZ channel designation.
Double periods will result in a filename if a station does not use location identifiers. The file name will look something like this: ANMO.IU..LHN.xxxx, representing the empty designation for a location ID. In SEED, an empty location ID is represented by two SPACE characters. To see if there are location identifiers used for a particular installation, use SeismiQuery’s channel tool and be sure to checkbox the "location" field to include this field in your query.