Use AFTrack for Sailing
AFTrack is available in 3 versions - all are usable for sailing:
There are some useful settings for sailors
be found in GPS settings,
wind speed units in Display settings
data can come from different devices. For online and bluetooth an extra
definition is needed.
Online GPS comes over TCP, UDP or as a Signal K websocket. For
websocket it is possible to define an address like an ip
When the incoming GPS signals are not satisfying, it is possible to
work in a mixed mode. The position messages from an external device are
ignored than and for position the internal GPS is used.
|GPS Mixed Mode
|Collect NMEA data from external
services (Bluetooth, Wifi, USB) but use the internal gps for prosition
settings, shows a wind arrow with feathers
settings, show an arrow from position to the probable position
in 10 minutes,
if AIS entries on display they also have an arrow.
settings, shows a wind information on map
With a tap on the wind info a pop up shows the wind settings
not internal is selected, the info shows the weather values of the
nearest station to the map center. This is updated every 5 minutes.
Other options show different results.
For use of an internal wind feature, please select this and press the
arrow to define a wind direction and speed by hand.
|When there is no input for
an external wind instrument this values are used.
settings, enable the use of wind informations for the GoTo or routing
settings, shows the laylines of the way point in GoTo mode
settings, defines best angle to wind and max speed
This values are used for wind routing calculation when no polar values
polar values from a file should be used check the box. The files should
be stored in AFTrack folder /data/aftrack/polar like
the default.csv CSV files are converted to a xml file and also placed
in polar folder.
settings, replaces the
profile dock view with an AIS list
|AIS small icons
||Show the AIS symbols in smaller layout and scale it when possible
|Show a path for a ship or for all ships
a group of ships in a seperate color. Please define a file with name
'aisgroup.txt' and place this into the AFTrack folder 'conf'.
The file contains a MMSI on each line.
|| Select the overlay button and set the alarm
For some clearing have a look to Wikipedia for Tacking or Jibe.
Main used chart format in AFTrack is the BSB format. You will find some sources here.
You may also use the NV-digital charts (this is encrypted BSB3 format).
The new NV-digital tiled format is also available, please do a map scan, when installed.
There are several other map formats for AFTrack: sqlite, mbtiles, mapsforge, osz, mph/mpr or jpg, png, bmp, tiff with calibration file
It is recommended to switch off the GPS first to get a clear planning
of a trip. Work with fixed values for wind and speed. Set the wind direction and
speed via the wind info dialog. Set the boat speed according to the expected wind in the display settings for wind (Not necessary when using polar data).
Press a point on the map for a longer time and select the ruler for a
route design. Add some points when needed.
The distance is not only calculated from the point to point distance.
It also contains the laylines from point to point when next point is
not reachable in a direct way.This is an idealistic way of view to the
route. The boat has to do some more tacks then the display shows.
Please keep in mind, we are not calculating current, drift, wave or
cost of maneuvers.
Use the wind instrument for an orientation.
The outer ring shows the boat direction and has the true wind in cyan
and a blue area for the one hour wind average with cyan center and the
direction of change on one end.And an arrow to the selected way point.
The inner circle shows the relative wind situation with the best tack
angles (from settings or from the polar values). Also a four minutes
average of the true wind relative to the boat which helps to assess teh
The view is in GoTo mode. It can switched of by pressing the GoTo button.
To stop the GoTo mode with sail routing press the motor button. GoTo mode calculates now for the direct way.
In the middle is a wind buttom shown. This is only visible when the wind values are manuell done. It can be used to adjust the wind direction.
This makes only sence when the defined wind angle for your boat is nearly correct and you are sailing on best way to wind.
Please keep in mind, the four minutes wind average can be better than
the best tack angle because there
are influences by waves and current. Before you edit the boat parameter
for that please have a look on the opposite site if there is the same
On a Trip you tap a way point and select the arrow button. This starts
the GoTo mode.
The route at GoTo mode start is displayed in magenta.
All other values are recalculated continuously. Notice the 10 minutes
position and the laylines of the way point.
Please keep in mind this is an idealistic view. Newer go direct to the
laylines accept the last half mile.
It is better to stay in the green area not to get in trouble when wind
Standard situations during sailing
Wind from direction of way point. Both legs are equal and there is no favorite side.
The Wind again comes from way point direction but way point isn't in
direct position. The course line is shown like this because ship is
going this direction.
But it's recommended to tack to come into the favorite area (dotted
lines) in the middle of tack angle to protect you for wind shifting.
Another problem is the current. AFTrack trys to calculate it from course over ground and course through the water.
In this case an extra line is shown (green line, this means not a star board line, it' only an opposite line).
Again it's recommended to tack as you see on the side. Layline 2 is shorter and will bring you to target ealier.
The green line ist shown when the gap of both distances are greater than 100 m - tack will cost you a little bit.
To help you with the correct cross track error (XTE) you could avtivate the corridor routing.
Set the Display Settings
Corridor Routing: on
Single Alarm: on
Route Alarm Distance: as you like, in meter
Wind Info: on
Wind Routing: on
Layline Wpt: on
Check also the boat parameters if it will work for your boat.
When wind is not running, you may set the 'internal' wind by tapping the
wind gauge. E.g. simulation at home.
Select a way point and press the got button (arrow)
You will have one of the situations in the pictures. Belongs to the wind
You will have an alarm when you leave the corridor. This is
switched off when you are back inside the corridor, or when you select
the 'stop' from the notification in the system status line. In this
dialog you also can select 'reset' to define a new starting point.
The alarm is also send to a bluetooth watch.
go against the wind:
This is different, you go to the first leg, but you
will get an alarm on changing towards the way point. So after the round
it is a good idea to do a reset when course becomes stable.
The displayed way is an idealistic one. I would newer go over the whole
leg, I would go round between the dotted line and the layline, not to
run in trouble with changing winds.
When in sailing routing and in the goto view of the app you will find an
engine button. You could switch the motor on (when you NMEA doesn't
contain sentences about this) and the goto mode is resetted to direct go
to the way point.
AFTrack has a feature which could be useful for regatta planning:
Insert a way point selection.
You have to activate this feature before using.
And you need a definition file with the name wptcollection.txt. A
sample is found in AFTrack folder conf. Build something like this:
# first line wpt group name, icon
And copy new icons to the AFTrack icon folder.
# all other are wpt: name, icon
When it is activated you have a new entry when you do a long press on
After pressing the third button a new way point group is added and you
have the collection icon on the map.
When you tap on this icon all related icons are shown around the
Move the points to its favorite places and send the waypoint group to
the participants by export.
Set the property of the group from 'As
Collection' to 'Visible' to see all points on the map.
Use extra hardware
Build your own GPSD on a Raspberry Pi
Use the OpenSeaMap logger project
Or get ready to use hardware from vYacht, iKommunicate, SailTimer Mini-Server
Best results reported with NMEA to WiFi interface from Comar Systems
Or use SEANEXX AIS-Receiver (USB direct or with wifi module)
Use a wireless Anemometer
To handle external devices with special specification AFTrack uses
plugins, see here for more information
One of these is for the SailTimer Wind Instrument™, an
autonomous and cableless mast head unit using Bluetooth
Low Energy for transfer
My travelling samples for independent sailing (usable with hand luggage):
Wind instrument (from SailTimer™ or Calypso), AIS USB stick, wifi router, power bank and AFTrack on a tablet