Digital Yacht GPS150 DualNav

[skipper680]

Hello everyone

I am considering buying this dual GPS/Glonass antenna/locator as the claimed increase in position accuracy is impressive.
My "legacy" GPS unit is a Lowrance LCX 110. This is a 12 satellite capable machine with NMEA 0183 antenna input.
Can someone please advise whether connecting the GPS150 DualNav mushroom( 50 satellite capacity) will indeed deliver the expected improvement?
In other words, is the built-in 12 sat receiver a fixed bottleneck or can the Dual Nav force-feed processed '50 satellite powered" data down the NMEA 0183 that the LCX110 can use, assuming of course correct DIP settings? Apologies if overlooking the obvious but no real idea how these devices work!
Many thanks

 

[pvb]

How accurate a position do you need? Most GPS units today give a position accurate to within a boat's length. Can't see why you'd want anything better than that, unless your eyesight's very bad.

 

[skipper680]

Thanks for your thoughts.

Accuracy does depend on the number of sats "visible" on your location at the time. Often in the Aegean with only 5 or 6 available , accuracy is down to 40-50m. Combining Glonass with GPS they claim 1 m, nice eg for fishing spot pinpointing, avoiding or identifying reefs etc, I always struggle to manage this with my bare eyes.

How acceptable " a boat's length" accuracy is, I guess depends on the "boat's length" and the circumstances, but can you ever have "too much accuracy" when navigating?.

 

[jerrytug]

Hello everyone

I am considering buying this dual GPS/Glonass antenna/locator as the claimed increase in position accuracy is impressive.
My "legacy" GPS unit is a Lowrance LCX 110. This is a 12 satellite capable machine with NMEA 0183 antenna input.
Can someone please advise whether connecting the GPS150 DualNav mushroom( 50 satellite capacity) will indeed deliver the expected improvement?
In other words, is the built-in 12 sat receiver a fixed bottleneck or can the Dual Nav force-feed processed '50 satellite powered" data down the NMEA 0183 that the LCX110 can use, assuming of course correct DIP settings? Apologies if overlooking the obvious but no real idea how these devices work!
Many thanks

I just looked at the online ad out of curiosity, and it definitely claims to be able to feed in to an ordinary plotter, or ipad etc, with a choice of baud rates. I don't believe it actually could work with a basic plotter properly, how would the different constellations be displayed etc? ( unless the plotter had previously been designed for two totally different sets of satellites).



I have a battered 15 yr old Garmin monochome plotter, the accuracy definitely does not get much worse if only 6 satellites are visible, 6 should be plenty. Perhaps your Lowrance has a little fault?

it's very interesting to know what is out there though!

 

[Andrew G]

I'll start by saying that I have just purchased a DY 150 but I haven’t fully commissioned it yet (next few days) (my old Raymarine 120 died – internal battery died after 10 years). My understanding is that whilst GLONASS coverage is excellent near Russia, and may be better than GPS nearer the Arctic, it is not yet fully global – it is still being implemented. No harm in being “GLONASS-ready” but you’ll be relying on GPS for a little while yet.
You only need 4 satellites to get a fix, but up to a point, the more the merrier. If you are in a region where “only 5 or 6 are available” then, no matter what brand of unit, that’s all that will be seen (unless there are GLONASS ones too). For a yacht, a limit of 12 channels (satellites) is not a practical limitation of accuracy, that is, +/- 10 to 50m is OK. The error on our electronic charts is possibly greater - so why do we need greater GPS accuracy? At that level we’ll be using our eyes, not just instruments.
The 150 does look an impressive unit and, if you already have NMEA 0183 (I don’t), installation is as hard as mounting it, replacing the old cable with the new and making four connections.
If my 12 channel unit hadn’t died I would not have replaced it with a 50 channel unit.
Cheers, Andrew
(If you do decide to get a new unit consider keeping your old unit as an emergency or for input to a DSC radio, although you could also connect your new unit to a radio)

 

[Sandy]

How acceptable " a boat's length" accuracy is, I guess depends on the "boat's length" and the circumstances, but can you ever have "too much accuracy" when navigating?.

I see you have a low post count so welcome to the Forum.

Others will disagree with your comment. You also need to understand how accurate the survey for the chart was. Back in 1850 I am not so sure that they were as accurate as the 2m accuracy my handheld GPS gives; checked against an Ordnance Survey datum point when I had nothing better to do.

 

[Buck Turgidson]

Accuracy isn't the only measure.

Availability and Continuity are equally important and both are improved by using 2 satellite constellations rather than 1.

 

[jerrytug]

Accuracy isn't the only measure.

Availability and Continuity are equally important and both are improved by using 2 satellite constellations rather than 1.

Hi Buck, what is meant by 'availability' ?
is it different to, 'what satellites are above the horizon' ?

 

[Buck Turgidson]

Hi Buck, what is meant by 'availability' ?
is it different to, 'what satellites are above the horizon' ?

What serviceable satellites are visible is a good enough definition in this context.
Continuity would be how long is there a usable constellation in view.

These terms are used in the implementation of GNSS based procedures in commercial aviation where navigation is now considered to be "Performance Based" i.e. the better the performance of the entire system, the smaller the spacing between aircraft and obstacles can be. This same philosophy equally applies to sailing with the caveat that the chart is part of the overall system and therefore if it is not very accurate then it becomes the most limiting part of the equation.

 

[skipper680]

Some fascinating info here, thanks to everyone who is contributing.

The best accuracy I' ve seen reported on my LCX110 was 5m with 12 sats visible including WAAS correction. If this was always the case I would not be looking further. I am after the potential benefit from using combined GPS/Glonass constellation. This could, in the worst case scenario, always allow me to see 12 sats with WAAS ( not the case now) giving me the best performance the Lowrance can give. In the best -and this was the thrust of my original question- if my LCX 110 could use the extra data, improve the "performance" of the system further in every aspect, ie lock on time, refresh , accuracy etc.

Jerrytag, my Lowrance will give a fix with only 5 sats ( GPS) but you do not get WAAS and this seems to have a serious impact.

Andrew G thanks, looking fwd to your feedback. I read somewhere that GLONASS have the full 24 sats up and operating since spring 2013?


Camelia thanks for the welcome, member from some time back, although first thread here. You are right of course about map accuracy, but errors are added together, worth trying to reduce the end sum. 2 m accuracy is fantastic, are you sure your handheld is not combining constellations . I was surprised to find out how many current mobile phones can "see" GLONASS

Buck thanks, very helpful, my thoughts exactly.

Can someone please clarify if the "mushroom" contains the satellite receiver (12 or 50 channel or whatever) and the box will display whatever is fed via the NMEA0183 or is it just an "antenna" and the satellite receiver lives inside the main unit box?