LOC record

In the Domain Name System, a LOC record (experimental RFC 1876) is a means for expressing geographic location information for a domain name.

It contains WGS84 Latitude, Longitude and Altitude (ellipsoidal height) information together with host/subnet physical size and location accuracy. This information can be queried by other computers connected to the Internet.

Record format

The LOC record is expressed in a master file in the following format:

<owner> <TTL> <class> LOC ( d1 [m1 [s1]] {"N"|"S"} d2 [m2 [s2]]
                            {"E"|"W"} alt["m"] [siz["m"] [hp["m"]
                            [vp["m"]]]] )

(The parentheses are used for multi-line data as specified in RFC 1035, section 5.1.)

where:

    d1:     [0 .. 90]            (degrees latitude)
    d2:     [0 .. 180]           (degrees longitude)
    m1, m2: [0 .. 59]            (minutes latitude/longitude)
    s1, s2: [0 .. 59.999]        (seconds latitude/longitude)
    alt:    [-100000.00 .. 42849672.95] BY .01 (altitude in meters)
    siz, hp, vp: [0 .. 90000000.00] (size/precision in meters)

An example DNS LOC resource record

• statdns.net for the coordinates: 52°22′23″N 4°53′32″E / 52.37306°N 4.89222°E / 52.37306; 4.89222 (StatDNS.net LOC record)

LOC record statdns.net.   IN LOC   52 22 23.000 N 4 53 32.000 E -2.00m 0.00m 10000m 10m

Altitude for Geosynchronous Earth Satellites

The altitude range provides the following:

• DNS altitude range [-100000.00 .. 42849672.95]. This range can be easily stored in 4 bytes.
• Maximum altitude is 42,849.67295 km. Which is large enough to store the altitude of a circular geosynchronous orbit (i.e. approximately 35,790 km above mean sea level).
• Maximum depth of 100 km below earth surface (approximated by the WGS84 reference ellipsoid).

Postcode to LOC in DNS using find.me.uk

You can look up the LOC record for any UK postcode, e.g.:

$ dig loc SW1A2AA.find.me.uk
SW1A2AA.find.me.uk.     2592000 IN      LOC     51 30 12.748 N 0 7 39.612 W 0.00

See also

• List of DNS record types
• Geo (microformat)
• Geolocation
• Geolocation API

References

• Lookup GPS coordinates in DNS - LOC lookup (Broken as of 2016-05-18)
• GeoTrace - Map a hostname or domain with a DNS LOC record
• DNS-LOC calculator for djbdns's tinydns
• Wikipedia:WikiProject Geographical coordinates The Wikipedia location resource.
• Sites supporting DNS LOC
• RFC 1876 - How latitude and longitude are stored in a DNS record.
• RFC 2426 Chapter 3.4.2: Text/directory MIME type GEO
• RFC 6350 Section 6.5.2: GEO (obsoleted RFC 2426, updated by RFC 6868)