Frequent Ask Questions

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I just installed an High Frequency GPS and now i have a « Bus collision » message what can I do?

Before installing this GPS you probably had a standard GPS logged on a NMEA input of your system. This NMEA input has been initialized and GPS channels have been created. The HF GPS also creates GPS channels on the bus hence the collision and the error message.

Solution :

  1. Disconnect the HF GPS and the Standard GPS.
  2. Turn on the system and initialize once again the NMEA input where the standard GPS was connected. The result must be « 0 channel created ». It clears out this NMEA input.
  3. Turn off the power and reconnect the HF GPS and the standard GPS.
  4. Turn on the system and create a waypoint. Then do a NMEA initialization. This will create GPS channels that are not created by the HF GPS such as the cross-track or the course and distance to waypoint.
I lost the True Wind Mode and speed over ground code, how can I do?

This code is calculated with the serial number of your autopilot control (Gyropilot 2). We maintain a database of delivered code, you can therefore ask us by email to send it to you.

The serial number is made up of 4 hexadecimal characters (from 0 (zero) to F). You can find it on a label stuck on the autopilot control or via the menu of your pilot remote control.

  • In the case of the Gyropilot Graphic: Main menu > Configuration > owner’s code > Options.
  • In the case of the Multigraphic: Main menu > Pilot > Speed over the ground option > speed over the ground code.
My AIS receiver or AIS Transponder is well connected to my Multigraphic but I can’t see the AIS page. How can I do?

You can first verify that AIS data enter in the Multigraphic via the console: Main menu > Parameters > Maintenance > Peripheral devices > Console.

You are supposed to see sentences such as:

!AIVDM,1,1,,A,14eG;o@034o8sd<L9i:a;WF>062D,0*7D
!AIVDO,1,1,,B,13PRrB0000OvbS@NhA9=oPbr0<0u,0*5

If it is not the case you must verify your physical installation.

If you do see those sentences you must activate the AIS page of your Multigraphic: Main menu > Screens, then select a free customizable screen.

Choose the « screen type », scroll down until « AIS ». Select « visible » in order to obtain a green check instead of a red cross. The page is therefore available. You’ll also need a compass and GPS data on the bus.

I just installed a wifi box (or usb box) but i can’t get some NMEA data. What is happening?

In order for NMEA data to get to the nke bus you have to « initialize » the matching input. This initialization corresponds to the creation of channels on the bus. On a WIFI or USB box the initialization is availaible thanks to a capacitive button. Press this button for 3 seconds (3 beep) while the device responsible for sending NMEA data (chart plotter, GPS, computer, tablet or mobile ) is indeed transmitting data. NMEA input (WIFI (UDP 50000), USB or RS232 (4800 to 38400 bauds)) strarts to analyze during 20 seconds data received. If these data match an available channel on the bus, the channel is created and the WIFI or USB box will be able to broadcast these data. At the end of the procedure you will ear 1 beep per channel created (listen carefully!). If the procedure fails , verify that data you want to get are already not created on another NMEA input, in which case the channel is therefore not available.

What is the « true wind / speed over ground » option?

True wind calculation
True wind calculation is based on 3 measured data: surface speed (Vb), apparent wind speed (Va) and apparent wind angle (Aa).

True wind speed: Vr = (Va2 + Vb2 – 2 Va Vb cos Aa)½
True wind angle: Ta = Aa + arcsin(STW sin Aa / Tw)

Surface speed reference
Many reasons can prevent from having a right surface speed measurement

  • The (log/speedo) sensor can be dirty. It’s usually the case with paddlewheel sensors that are never removed from the boat. You would need to remove it from the thru-hull fitting when not sailing. But this procedure is arduous.
  • A boat does not sail on its axis (leeway), and the hull divert water. These deviations change depending on the heeling. The hull also creates a disrupted layer called « boundary layer » where water is slowed down by the contact with the hull. Depending on the electronic equipment we can either calibrate the sensor using a simple coefficient or a full table, taking into account the tack and the heeling. An ultrasound calculation (ultrasonic speedo) allows to measure outside the boundary layer and therefore cancel the bias.
  • Some boats with light displacement have a hull’s part outside water when planning. It is consequently difficult to find a hull’s spot constantly submerged in water. Most of the time the log/speedo is installed in front of the keel. However it’s not uncommon to see this part of the boat out of water when planning, making the sensor ineffective. In that case it is possible to install 2 lateral sensors at the third back of the boat. A sensor’s automatic selector will switch from one side to the other depending on the tack.

©Th.Martinez/Sea&Co. LA TRINITE SUR MER – – FRANCE 20 mai 2014. Départ de la course en solitaire La MINI en Mai, organisé par la SNT. MONOHULL, MONOCOQUE, MINI EN MAI, 865, CULTISOL, Davy Beaudart

The speed over ground is not impacted by these disruptions and offers us a more reliable source of speed. When it comes to sailing with autopilot in true wind mode this speed source accuracy becomes essential. If the boat’s speed falls to 0 knot, true wind angle (twa) equals to apparent wind angle (awa). Let’s imagine the following situation :

  • Apparent wind angle : 140°
  • Apparent wind speed : 12 knots
  • Boat’s speed : 15 knots

The true wind calculated is of approximately 25 knots for a 160° angle. If the speed drops to 0, the new true wind angle will be 140° (equal to the apparent wind) and the pilot will pull the tiller to be in accordance with the initial set point (160°), that is to say bearing away at 20°. The boat slows down and the apparent wind angle increases. Then the autopilot pushes the tiller to luff. This becomes quite chaotic.
Polar speed of a boat are established on a surface speed basis, this calculation based on the speed over ground is therefore useful for the pilot but not for the performance measure. On cruise it’s also a very interesting speed reference.

Speed over ground reference
How getting a true wind calculation based on the speed over ground when we have nke instruments? You have to switch from surface speed to speed over ground on the bus. It is the log/depth sounder which provides this surface speed. When you have a log/depth sounder in a 2.1 modified version, if you select « speed reference : speed over ground » in pilot parameters, the log/depth sounder supplies the surface speed channel with the speed over ground that it receives via the bus.
In order to make sure this works properly it exists a simple procedure which can be made at berth.

  1. Set the surface speed filter at 1. This allows to read the raw data without delay.
  2. Select surface speed and speed over ground channels on your display. Even off we still observe a speed over ground different from 0.
  3. If you selected the surface speed as reference in your pilot, you should read a surface speed different from the speed over ground.
  4. If you selected the speed over ground as reference in your pilot you should read identical data on both channels with a potential slight time difference.

Warning
Calculate a true wind angle based on the speed over ground requires a responsive source, high frequency and low latency. The most adapted sensor is therefore the nke HF GPS.

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