Magnetic bearing to AIS target?
- Thread starter lshick
- Start date
A
Anonymous
Guest
Ishick,
To select the range ring mode first select the (Radar)-(Bearing Scale Mode)menu of the main menus of then you will be given the option to select Relative or True
Heads up Mode
Relative-bearing scale is fixed and "0" is at top of the screen
True-Bearing scale rotates according to the movement of the ship
North-up mode
Relative-Bearing scale rotates according to the movement off your ship
True-Bearing scale is fixed and "0" is at the top of the screen.
Regards,
Mr.Radar
To select the range ring mode first select the (Radar)-(Bearing Scale Mode)menu of the main menus of then you will be given the option to select Relative or True
Heads up Mode
Relative-bearing scale is fixed and "0" is at top of the screen
True-Bearing scale rotates according to the movement of the ship
North-up mode
Relative-Bearing scale rotates according to the movement off your ship
True-Bearing scale is fixed and "0" is at the top of the screen.
Regards,
Mr.Radar
No joy.
On both my TZT9 and TZTL12F I have "Bearing Scale Mode" set to True. Yet the AIS "info" pages for AIS targets report bearings as relative (not labeled as such, but eyeball and math confirm that's what they're reporting).
For example just now I have a target to the ENE of me, on my stern. The AIS report puts it at 171 degrees bearing, which is a correct relative bearing but not the true (or magnetic, which I'd prefer) bearing.
On both my TZT9 and TZTL12F I have "Bearing Scale Mode" set to True. Yet the AIS "info" pages for AIS targets report bearings as relative (not labeled as such, but eyeball and math confirm that's what they're reporting).
For example just now I have a target to the ENE of me, on my stern. The AIS report puts it at 171 degrees bearing, which is a correct relative bearing but not the true (or magnetic, which I'd prefer) bearing.
While bearing mode is setup for True, what bearing shows when using your cursor bearing with the cursor on top the AIS target, or when you use your radar EBL line to the AIS target?
Thanks for your reply.
On the TZT9, with Bearing Scale Mode = True and EBL Reference = True, the AIS panel shows bearing 143 deg, selecting a point on the same radius shows 132 deg (we're at anchor and moving around a bit), and the EBL shows 092 (clearly labeled Magnetic). This was on a heading of roughly 300 deg M, so the math works out plausibly close: 300 M heading + 143 relative = 443 M bearing, less 360 = 083 M bearing.
So the EBL happily gives me a magnetic bearing, but I haven't figured out how to get either AIS or point-select to do so.
By the way, same results with the TZTL12F. Current software on both units.
On the TZT9, with Bearing Scale Mode = True and EBL Reference = True, the AIS panel shows bearing 143 deg, selecting a point on the same radius shows 132 deg (we're at anchor and moving around a bit), and the EBL shows 092 (clearly labeled Magnetic). This was on a heading of roughly 300 deg M, so the math works out plausibly close: 300 M heading + 143 relative = 443 M bearing, less 360 = 083 M bearing.
So the EBL happily gives me a magnetic bearing, but I haven't figured out how to get either AIS or point-select to do so.
By the way, same results with the TZTL12F. Current software on both units.
D
DB Cooper
Guest
Larry,
No, you are unable to change the bearing mode of an AIS target.
All AIS targets will display in relative to the bow of your boat. But of course if you're a curious person like me, then we ask the question why? :sorry
So lets say we are navigating through low visibility conditions in a very busy harbor. And we see an AIS target headed straight for us on our TZT...
If we had the AIS bearing in magnetic and for some reason that huge freighters AIS signal drops out and all we are left with was the last known magnetic bearing before his AIS signal loss. We would then have to avert our attention to a heading compass to verify our magnetic heading to then determine and estimate his location to avoid a potential collision.
Now, same scenario but with the AIS bearing displaying in relative(how it displays on the TZT)... All we would have to do is see that his last known bearing (before his AIS signal was lost) was, lets say 279 degrees, and we can directly avert our attention off the port side quickly and prepare for evasive maneuvers if needed.
So quite simply, its a safety precaution.
No, you are unable to change the bearing mode of an AIS target.
All AIS targets will display in relative to the bow of your boat. But of course if you're a curious person like me, then we ask the question why? :sorry
So lets say we are navigating through low visibility conditions in a very busy harbor. And we see an AIS target headed straight for us on our TZT...
If we had the AIS bearing in magnetic and for some reason that huge freighters AIS signal drops out and all we are left with was the last known magnetic bearing before his AIS signal loss. We would then have to avert our attention to a heading compass to verify our magnetic heading to then determine and estimate his location to avoid a potential collision.
Now, same scenario but with the AIS bearing displaying in relative(how it displays on the TZT)... All we would have to do is see that his last known bearing (before his AIS signal was lost) was, lets say 279 degrees, and we can directly avert our attention off the port side quickly and prepare for evasive maneuvers if needed.
So quite simply, its a safety precaution.
Karlgleaves
New member
Two big pluses for Furuno and this Forum. Furuno technical support is absolutely the best in marine electronics industry. Likewise, hats off to the moderators and supporters of this forum.
But one HUGE minus, i.e., the failure to show the bearings to AIS targets in magnetic. On this issue I very strongly disagree with moderator DB Cooper that this is a safety issue. First of all , it is highly patronizing to suggest Furuno knows better than users what bearing mode for AIS works best for them. Furuno doesn’t mandate only North Up or only Heading Up for chart orientation based on which orientation is “safest.” Why on this issue? And even if Furuno really thinks relative bearings are a big deal and are best, why not allow the actual user to use their own preferred system? Anyway if magnetic bearing settings for AIS targets are so unsafe, why are they available on Furuno’s commercial chart plotters, as well as most other plotters for recreational boats made by other manufactures. Using your logic those plotters must have a safety issue, right? Maybe someone should warn the Coast Guard.
Secondly, for me relative bearings are unsafe. It may be true that some boaters may instinctively think of 90 degree bearing as off the starboard beam, but that doesn’t mean it’s that is true for everyone. It is also easy to glance at the ship’s compass and identify the general area where the AIS target is likely to be located based on a magnetic bearing. More importantly if you are trying to identify a specific target (say a high speed hydrofoil ferry coming out of a harbor along with a three or four other vessels with AIS). A good hand bearing compass and the AIS magnetic bearing allows me to quickly identify the specific target of concern and carefully watch its approach. Likewise, knowing the precise magnetic bearing gives a much more specific area to watch if the target disappears as in the scenario you raised, without complicated calculations.
To distinguish among multiple targets in the same general vicinity when only a relative bearings are known requires requires adding the relative bearing(s) to the ship’s heading of the vessel and then sometimes subtracting 360; so you better be quick at adding, have a pencil and paper handy or a waterproof calculator handy (or maybe all three) and then hope your eyes adjust from the light needed for the calculations to the darkness and vague and confusing dim lights you are trying to distinguish and identify (hard for my old eyes). THIS IS INSANE. Furuno could do a quick software update and fix this problem quickly.
I HIGHLY RECOMMEND THAT ALL FURUNO DEALERS ADVISE ALL PROSPECTIVE PURCHASERS OF THE TCT3 CHART PLOTTERS THAT SOME PAST PURCHASERS (or at least me) ARE EXTREMELY UPSET BECAUSE BEARINGS AIS TARGETS ARE SHOWN ONLY AS RELATIVE BEARINGS AND VIEW THIS AS DEFECT WHICH IS UNSAFE.
Anyway, sorry about the rant but I truly wish we had tried to repair our old (ancient) Furuno Navet 2 system which did show AIS targets as a magnetic bearing or purchased a different brand of chart plotter. The TCT3 has a great display and seems fairly easy to use but this defect is a serious and Furuno needs to do something about it.
But one HUGE minus, i.e., the failure to show the bearings to AIS targets in magnetic. On this issue I very strongly disagree with moderator DB Cooper that this is a safety issue. First of all , it is highly patronizing to suggest Furuno knows better than users what bearing mode for AIS works best for them. Furuno doesn’t mandate only North Up or only Heading Up for chart orientation based on which orientation is “safest.” Why on this issue? And even if Furuno really thinks relative bearings are a big deal and are best, why not allow the actual user to use their own preferred system? Anyway if magnetic bearing settings for AIS targets are so unsafe, why are they available on Furuno’s commercial chart plotters, as well as most other plotters for recreational boats made by other manufactures. Using your logic those plotters must have a safety issue, right? Maybe someone should warn the Coast Guard.
Secondly, for me relative bearings are unsafe. It may be true that some boaters may instinctively think of 90 degree bearing as off the starboard beam, but that doesn’t mean it’s that is true for everyone. It is also easy to glance at the ship’s compass and identify the general area where the AIS target is likely to be located based on a magnetic bearing. More importantly if you are trying to identify a specific target (say a high speed hydrofoil ferry coming out of a harbor along with a three or four other vessels with AIS). A good hand bearing compass and the AIS magnetic bearing allows me to quickly identify the specific target of concern and carefully watch its approach. Likewise, knowing the precise magnetic bearing gives a much more specific area to watch if the target disappears as in the scenario you raised, without complicated calculations.
To distinguish among multiple targets in the same general vicinity when only a relative bearings are known requires requires adding the relative bearing(s) to the ship’s heading of the vessel and then sometimes subtracting 360; so you better be quick at adding, have a pencil and paper handy or a waterproof calculator handy (or maybe all three) and then hope your eyes adjust from the light needed for the calculations to the darkness and vague and confusing dim lights you are trying to distinguish and identify (hard for my old eyes). THIS IS INSANE. Furuno could do a quick software update and fix this problem quickly.
I HIGHLY RECOMMEND THAT ALL FURUNO DEALERS ADVISE ALL PROSPECTIVE PURCHASERS OF THE TCT3 CHART PLOTTERS THAT SOME PAST PURCHASERS (or at least me) ARE EXTREMELY UPSET BECAUSE BEARINGS AIS TARGETS ARE SHOWN ONLY AS RELATIVE BEARINGS AND VIEW THIS AS DEFECT WHICH IS UNSAFE.
Anyway, sorry about the rant but I truly wish we had tried to repair our old (ancient) Furuno Navet 2 system which did show AIS targets as a magnetic bearing or purchased a different brand of chart plotter. The TCT3 has a great display and seems fairly easy to use but this defect is a serious and Furuno needs to do something about it.
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