Is something wrong with seatalk 1 ap for track follow? about signalk-autopilot

[joabakk]

Hi,

I don't think track mode was ever fully implemented. There was a requirement that the next waypoint. See https://github.com/SignalK/signalk-autopilot/blob/master/raymarinest.js#L176-L184

There is very little information about this available, so development stopped here

[ckcrs]

Thanks.
Sometime ago I've found info about seatalk, I guess sourced from openplotter related document, I hope, this helps for any developer/maintainer of code.

"85  X6  XX  VU ZW ZZ YF 00 yf   Navigation to waypoint information 
                  Cross Track Error: XXX/100 nautical miles 
                   Example: X-track error 2.61nm => 261 dec => 0x105 => X6XX=5_10 
                  Bearing to destination: (U & 0x3) * 90° + WV / 2° 
                   Example: GPS course 230°=180+50=290 + 0x64/2 => VUZW=42_6 
                   U&8: U&8 = 8 -> Bearing is true, U&8 = 0 -> Bearing is magnetic 
                  Distance to destination: Distance 0-9.99nm: ZZZ/100nm, Y & 1 = 1 
                                           Distance >=10.0nm: ZZZ/10 nm, Y & 1 = 0 
                  Direction to steer: if Y & 4 = 4 Steer right to correct error 
                                      if Y & 4 = 0 Steer left  to correct error 
                  Example: Distance = 5.13nm, steer left: 5.13100 = 513 = 0x201 => ZW ZZ YF=1_ 20 1_ 
                           Distance = 51.3nm, steer left: 51.3*10  = 513 = 0x201 => ZW ZZ YF=1_ 20 0_ 
                  F contains four flags which indicate the available data fields:
                           Bit 0 (F & 1): XTE present
                           Bit 1 (F & 2): Bearing to destination present 
                           Bit 2 (F & 4): Range to destination present 
                           Bit 3 (F & 8): XTE >= 0.3nm 
                       These bits are used to allow a correct translation from for instance an RMB sentence which 
                       contains only an XTE value, all other fields are empty. Since SeaTalk has no special value 
                       for a data field to indicate a "not present" state, these flags are used to indicate the 
                       presence of a value. 
                   In case of a waypoint change, sentence 85, indicating the new bearing and distance, 
                   should be transmitted prior to sentence 82 (which indicates the waypoint change). 
                   Corresponding NMEA sentences: RMB, APB, BWR, BWC, XTE
"