Škola jedrenja za neznalice > Jedrenje za početnike

Q: Kojim sve metodama se može dobiti prognoza nasred Atlantika?

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pekZG:
Pitanje iz subjekta :)

Stavio bi fokus na Weather Fax i Text Forecest pokušao pokrenuti diskusiju u tom smjeru :)
Što je sve potrebno za dekodiranje slike i teksta?

janko_ka:
Pratim, zanimljiva tema, obično dobivaju file prognoze pa to repliciraju u nekim od laptopa, tableta,, file stiže preko SSB radio stanice.. Ima na netu sve pa valjda i to, ali zanima me u stvarnom životu kako to radi.

pekZG:
@Janko: Ovo što si opisao je dohvat GRIB fajlova kroz email najčešće putem pactor modema koji je spojen na SSB. Možda ako ovdje ima kakav radio amater može objasniti u detalje.
Bilo bi interesantno istražiti koliko bi koštala takva oprema i zapravo koliko se koristi u današnje vrijeme. Ima li tko ovdje da je bio u situaciji da je offshore i što je koristio za prognozu?

Mene više interesira weather fax i text forecast (koji sam vidio da isto emitiraju kao sliku) jer mi izgleda kao da je jeftinije ući u to;

---
Evo primjer ako želiš vidjeti kako to izgleda;
Prvo u ovih 130 stranica nađeš vrijeme emitiranje željene prognoze :D
https://www.weather.gov/media/marine/rfax.pdf

Nakon toga potraži slobodan SDR
http://kiwisdr.com/public/

Za primjer idemo vidjeti za Europu

--- Code: ---EUROPE
ATHENS, GREECE---------------------------------------------------------------------------------------------------------------- VI-1
MURMANSK, RUSSIA------------------------------------------------------------------------------------------------------------ VI-1
HAMBURG-PINNEBERG, GERMANY----------------------------------------------------------------------------------------- VI-2
NORTHWOOD, UNITED KINGDOM------------------------------------------------------------------------------------------ VI-3
--- End code ---

Potražiti ćemo nešto u Velikoj Britaniji jer oni stalno emitiraju;
Postoji time table kada se što emitira; kao da imaš TV program :D


--- Code: ---0000/1200 SURFACE ANALYSIS 120/576 18/06
0012/1212 24 HOUR SURFACE PROGNOSIS 120/576 18/06
0024/1224 24 HOUR 850 hPA WBPT / PPTN 120/576 18/06
0036/1236 24 HOUR OAT and TD 120/576 18/06
0048/1248 SHIP ICE ACCRETION 120/576 12/00
0100/1300 SCHEDULE 120/576
0112/------ SYMBOLOGY 120/576
0124/------ QSL REPORT 120/576
0136/1336 OCEAN FRONTS 120/576
0148/1348 300 hPA GPH 120/576 18/06
0236/------ SURFACE ANALYSIS 120/576 0000 -------/1400 SEA SURFACE TEMP 120/576 0000
0300/1436 SURFACE ANALYSIS 120/576 00/12
0400/1500 SURFACE ANALYSIS 120/576 00/12 -------/1512 24 HOUR ANPS PROGNOSIS 120/576 0000 -------/1524 120 HOUR ANPS PROGNOSIS 120/576 0000 -------/1600 SURFACE ANALYSIS 120/576 1200
0412/1612 24 HOUR OAT and TD 120/576 00/12
0424/1624 24 HOUR 850 hPA WBPT / PPTN 120/576 00/12
0436/1636 24 HOUR SURFACE PROGNOSIS 120/576 00/12
0448/1648 SCEXA TAFS 120/576 06/18
0500/1700 SURFACE ANALYSIS 120/576 00/12
0512/1712 24 HOUR SURFACE PROGNOSIS 120/576 00/12
0524/1724 48 HOUR SURFACE PROGNOSIS 120/576 00/12
0536/1736 SCEXA TAFS 120/576 06/18
0600/------ NWEXAS TAF COLLECTIVE 120/576
0612/1800 SURFACE ANALYSIS 120/576 00/12 -------/1812 24 HOUR SURFACE PROGNOSIS 120/576 1200 -------/1824 NWEXAS TAF COLLECTIVE 120/576
0648/1848 SCEXA TAFS 120/576 07/19 -------/1900 THICKNESS/GPH ANALYSIS 120/576 1200
0712/1912 24 HOUR SIGNIFICANT WINDS 120/576 00/12
0724/1924 48 HOUR SURFACE PROGNOSIS 120/576 00/12
0736/1936 72 HOUR SURFACE PROGNOSIS 120/576 00/12
0748/1948 96 HOUR SURFACE PROGNOSIS 120/576 00/12
0800/2012 120 HOUR SURFACE PROGNOSIS 120/576 00/12
0812/------ THICKNESS/GPH ANALYSIS 120/576 0000
0824/2024 48 HOUR SIGNIFICANT WINDS 120/576 00/12
0836/2036 72 HOUR SIGNIFICANT WINDS 120/576 00/12
0848/2048 96 HOUR SIGNIFICANT WINDS 120/576 00/12
0900/2100 SURFACE ANALYSIS 120/576 06/18
0912/2112 THICKNESS/GPH ANALYSIS 120/576 00/12
0924/2124 24 HOUR THICKNESS / GPH PROGNOSIS 120/576 00/12
0936/2136 24 HOUR 850 hPa SPOT WINDS 120/576 00/12
0948/2148 24 HOUR 700 hPa SPOT WINDS 120/576 00/12
1000/2200 SURFACE ANALYSIS 120/576 06/18
1012/2212 24 HOUR SURFACE PROGNOSIS 120/576 06/18
1024/2224 24 HOUR REDUCED VISIBILITY 120/576 06/18
1036/2236 24 HOUR 850 hPA WBPT / PPTN 120/576 06/18
1048/2248 24 HOUR OAT and TD 120/576 06/18
1100/------ SURFACE ANALYSIS 120/576 0600
1112/------ 24 HOUR SURFACE PROGNOSIS 120/576 0600
1124/2336 24 HOUR SEA and SWELL 120/576 06/18
1136/------ 24 HOUR THICKNESS / GPH PROGNOSIS 120/576 0000

--- End code ---

Na žalost dok sam ovo tipkao, prošlo je emitiranje pa nisam ništa ulovio :D
Bacim sliku kada ulovim priliku



Ono što ne znam je kako i sa čime dekodirati weather text?
http://weather.gmdss.org/I.html

----
EDIT:
Evo primjer mog pokušaja lovljenja weather fax-a :D

pekZG:
@Janko: nakon malo istraživanja polovio sam da navtex i slični nisu ništa drugo nego TTY, tj RTTY (Radio teletypewriter);

Kao i terminali na linux mašinama tty1 tty2 itd;
https://en.wikipedia.org/wiki/Tty_(Unix)

Ono što je interesantno kod rtty je što kao i stari dail up modemi koristi error correction (ima zalihosti ili redundancije u informaciji koja se prenosi), tako da osoba na drugoj strani može prilikom lošijeg prijema još napraviti par ispravaka;

Evo primjera error correction kodinga
https://en.wikipedia.org/wiki/Error_correction_code#List_of_error-correcting_codes


--- Code: ---RTTY, using either AFSK or FSK modulation, is moderately resistant to vagaries of HF propagation and interference, however modern digital modes, such as MFSK, use Forward Error Correction to provide much better data reliability.
--- End code ---

E sada što ti sve treba od softwarea da to dekodiraš?

pekZG:
fldigi je recimo jedan od software na koji sam naišao za dekodiranje RTTY-a :)

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