Furuno NavNet Radar Overlay

[Halcyon]

My boat came equipped with the Furuno Navnet system consisting of, I believe, a 1833C Radar, a GD 1700c plotter and a network sounder. The dispaly menu offers and 'overlay' option so you can show radar on the chart. This sounds great but I can't seem to get the radar to orient itself with the chart.

Oddly the two have different 'presentation modes' options:
Plotter: North Up, Course Up (course to a waypoint or the cursor) and Auto Course Up ( keeps the chart Course up and changes when boat turns more than 22.5 d.

Radar: Head-up (boat heading at top) Course Up (as above) North Up (as above) and True Motion (sounds like it readjusts when the image reaches the edge of the screen)

Overlay has and option on screen not mentioned in the manual, AT CU. Does anybody know what that means?

Being tought by a WWII Air navagation instructor, North up is the only way to orient your chart, damit. However hard old habits are to change, I see with radar having boat current heading up should produce the most usable information.

I am having difficulty getting the two images, chart and radar to synchronize. I am confused exactly where to enact the setting and if all the screens need to be set the same. The presentation mode can be selected in the plotter mode, radar mode and overlay mode. I have tried setting all to North up, because that is the most useable option they have in common. The allignment is off by maybe 20 degrees? I have seen it 90d counter clockwise to the plotter.

Does anybody out there use 'overlay' and if so how is yours set up? I would like both to be set heading up.

Finally, when I am messing with this at the dock, how does the system know north or heading? Doesn't GPS require motoin to determine these?

Many thanks TD

[mhanna]

You are correct in the the overlay will require a direction so that the GPS and radar pictures 'sync'. I do not have Furuno but with my Raymarine the only way to get correct overlay is to have an electronic compass connected to the system. In my case I have a Raymarine autopilot and that takes care of giving the system the boat course. If I turn the system on at the dock the radar knows what the front of the boat is, but the GPS does not know unless you have a compass. With this the system can do a proper overlay. Some systems may not let you do an overlay without it.

I use heading up mode all the time and it seems much easier to use because everything is in reference to the boats position.

I know a few out there with Furuno's and I am sure they can give us more specifics to that system.

Matt

[RobS]

Does anybody out there use 'overlay' and if so how is yours set up? I would like both to be set heading up.

Finally, when I am messing with this at the dock, how does the system know north or heading? Doesn't GPS require motoin to determine these?

Many thanks TD

I use overlay and when I am running it's set on Course Up, and when I am drifting I will use either Course Up or North Up. When I am on the hook or docked I will switch to North Up. When you are running Course Up and Heading Up are close to the same, depending on crosswinds and crosscurrents. The Heading Line will be displayed. See the green and red vector lines in my photo. Here is a shot of Overlay with trails set on. My friend is following me and is clearly shown on the radar with his trail. Presentation is Course Up. Heading and Course vectors can be seen. The actual radar hits on land (displayed in red) overlay the land displayed on the chart (displayed in yellow). Click on image for a larger view.

2011-05-31_10-47-00_226.jpg

As far as at the dock the system knows North & Heading via the heading sensor. This is the PG500 in the Furuno NavPilot 511 autopilot system. The GPS needs motion to determine Course, but North & Heading are independent of motion/course.

You don't mention Autopilot? You need a heading sensor to do overlay. Without a heading sensor my navnet2 will not even let you select the Overlay display. Do you have Autopilot? Or perhaps just a heading sensor? It is possible to have a heading sensor on the network without the rest of the Autopilot componets..

[RobS]

...Overlay has an option on screen not mentioned in the manual, AT CU. Does anybody know what that means?

I just re-read your post and realized there was another question in there. AT CU is Automatic Course Up. CU is Course Up. They two differ when you enter a destination into the chartplotter. If you have a destination (go to waypoint) entered, AT CU will put your boat's actual course up, CU will put the course to your destination up.

[Halcyon]

Thanks for the responses. The boat does have a Simrad AP 20 with a fluxgate compass I have no idea if there is a Furuno heading sensor or if the Simrad is being used (or can be used) as a heading sensor.
I seem to recall a set up screen that showed connected components when I was looking for transducer choices. I recall seeing the radar and GPS but not the sounder and no heading sensor.

I'm also not sure if this system has a 'HUB'. I guess I need to follow wires around some more.

RobS, I'm guessing I only need to set the presentation mode when in "overlay"? If there is no heading sensor will any of the Presentation Modes overlay properly or is the radar 'lost'?

thanks again TD

[RobS]

I doubt there is a Furuno heading sensor since there is a Simrad fluxgate as part of your autopilot. The fluxgate should be able to providing the heading data to your network for overlay to work properly. You may need some adapter, like SimNet to NMEA, etc. You should make a paper chart of your components and connections and then call Furuno's tech support. They offer excellent support and offer especially good support on "yesterday's" gear...