NOTAM Latitude / Longitude

Guest Discussion
1

Can someone point me to a document which describes the use of latitude and longitude in NOTAMs? I’m trying to read this NOTAM:
!GPS 09/039 ZDC GPS UNRELIABLE WITHIN A 270 NM RADIUS OF 305000N/0802500W AT FL400. THIS AREA DECREASES WITH ALTITUDE TO A CIRCLE OF RADIUS 225NM AT FL250 THEN TO A CIRLCE OF RADIUS 160NM AT FL100 DOWN TO A CIRLCE OF RADIUS 115NM AT 4000 AGL. IFR OPERATIONS BASED UPON GPS NAVIGATION SHOULD NOT BE PLANNED IN THE AFFECTED AREA DURING PERIODS INDICATED. THESE OPERATIONS INCLUDE DOMESTIC RNAV OR LONG RANGE NAVIGATION REQUIRING GPS. THE OPERATIONS ALSO INCLUDE GPS STANDALONE AND OVERLAY INSTRUMENT APPROACH OPERATIONS 1500-1900/2300-0300 DLY WEF 0309131500-0309180300

Usually they also give a radial/distance from a VOR in NOTAMS which makes it easier to find; but in this case I can’t tell if “305000N/0802500W” means 30 degrees, 50 minutes, 00 seconds N, 80 degrees, 25 minutes, 00 seconds W, or whether it means 30.5 degrees N, 80.25 degrees W, etc.

Thanks!

2

Steve,

This screen shot of a notam decoding program interprets lat/longs as DDMMSS.

You could also use the Monte Carlo method and sample a bunch of NOTAMs. If you don’t find any value greater than 59 in the 2nd and third digit pairs, it seems likely that they are MMSS and not MM.mm.

-Mike

3

Steve,

You’d think this would be clarified in http://www1.faa.gov/atpubs/NTM/INDEX.HTMAir Traffic Publication 7930.2H, which explains how to compose notams, but I haven’t been able to find it.

Cheers,
Roger

4

In Reply To:
…I can’t tell if “305000N/0802500W” means 30 degrees, 50 minutes, 00 seconds N, 80 degrees, 25 minutes, 00 seconds W, or whether it means 30.5 degrees N, 80.25 degrees W, etc. …

Actually, it means 30 degrees, 50.00 minutes N, 80 degrees 25.00 minutes W. …added later…(Which functionally is the same as your first interpretation, BTW [:)]) The first two digits of latitude are the degrees, the last four digits are minutes and one-hundredths of minutes. The first three digits of longitude are the degrees and the last four digits are the minutes and one-hundredths of minutes.

(from “Notam and weather contractions translator” FAA Air Traffic Publications Branch, ATA-10, January 1999) See Also the Directory Legend section of any Airport/Facility Directory.

5

Thanks Bill!