afi met bulletins exchange (ambex) handbook - ICAO

AFI Regional SIGMET Guide Page 33/60
APPENDIX F: Standard for Reporting Geographical Coordinates in SIGMET
When reporting geographical coordinates of points in SIGMET the following should apply:
1. Each point is represented by a latitude/longitude coordinates in whole degrees or degrees and
minutes in the form:
N(S)nn[nn] W(E)nnn[nn]
Note: There is a space between the latitude and longitude value.
Examples: N0518 W00401 Abidjan
S0419 E01519 Kinshasa
N1443 W01728 Dakar
2. In describing lines or polygons, the lat,lon values of the respective points are separated by the
combination space-hyphen-space, as in the following examples:
N1334 W00739 – N1327 W01635 – N0932 W1340– N0518 W00401 (Bamako, Banjul, Conakry,
Abidjan)
S05 E093 – N01 E095 – N12 E110 – S08 E103
Note: It is not necessary to repeat the first point when describing a polygon.
3. When describing a volcanic ash cloud approximate form and position, a limited number of points,
which form a simplified geometric figure (a line, or a triangle, or quadrangle, etc.) should be used in order
to allow for a straightforward interpretation by the user.
4. Reporting a phenomenon occupying two different geographical areas within the FIR. This is
frequently the case with two (or more) separate TS formations occurring in different parts of the FIR at
the same time. The question is whether a separate SIGMET should be issued for each formation, or, one
SIGMET could include location description for two (or more) geographical areas. The current SIGMET
format does not allow for reporting of more than one phenomenon or two different TS areas. Therefore, in
cases like this, two separate SIGMETs should be issued. The main concern with issuing separate
SIGMETs is that, in general, a new SIGMET for the same FIR would replace the previous one; this may
lead to rejecting valid information in case as described above. It should be noted in this regard, that the
current SIGMET format allows for using different sequence numbers and thus, for keeping more than one
SIGMET at a time valid for the FIR concerned; for instance, a series A1, A2,… could be used for
“phenomenon A” and B1, B2, … , for “phenomenon B”.
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Ninth Edition September 2007 Amend1/2010