AIS..how accurate is yours???

[StuM]

Originally Posted by dridas

Hey Jim. You might ask if there GPS receiver is WAAS (wide area augmentation system) compatible. If they are foreigners, from outside the US, it's possible their GPS is not set up for WAAS. Normal GPS, actually old GPS systems, had an accuracy of 100m.

If I understand WAAS correctly, GPS signals (not all of them) are updated with corrections that account for changes in the ionisphere, which brings accuracy down to a few meters. If the AIS is broadcasting location data that is not predicted, corrected, or accurate, the location will not be stable.

As far as I know Australia still does not have any SBAS (Satellite Based Augmentation System) in operation.

WAAS is specifically North American.

Don't know if this is still the case, but a few years ago, enabling WAAS on GPSs in this region significantly degraded the accuracy.

[StuM]

Originally Posted by Jim Cate

Ok, I'll see if I can find them on board. It is the only other overseas yacht here at present... we heard them negotiating clearance with Customs as they approached a while back,but have not seen them on board (a longish walk to where their berth is, so we don't check too often).

cheers,

Jim

If they are an overseas boat, maybe they have WAAS enabled and that is causing the inaccuracy (see my previous post).

[RaymondR]

I had a receive only unit lying about the boat which I finally hooked up to my nav computer and other boat positions were showed on the OCPN display. I am sufficiently impressed with the system that I am going to put a transceiver unit on the new boat. It was great to be able to identify other vessels by name and call using their call signs. Accurate or not it is a pretty impressive system.


Lot of home brewing retirees around Moreton Bay, maybe the boat is still and it's the ground moving???

[Paul L]

Originally Posted by StuM

As far as I know Australia still does not have any SBAS (Satellite Based Augmentation System) in operation.

WAAS is specifically North American.

Don't know if this is still the case, but a few years ago, enabling WAAS on GPSs in this region significantly degraded the accuracy.

This is the error I was referring to earlier in this thread. SBAS (satellite augmentation) is available in many areas N. America, Europe ,Japan, India . It does not cover Aus/NZ. On my SRT based AIS system if it is enabled while in NZ area it causes significant jumping position errors. Disabling it makes it solid. If your AIS uses the ProAIS host software then it is an SRT unit.

[barnakiel]

WAAS in Europe?

Where?

Every time I switch the WAAS on, position accuracy decreases.

I thought WAAS is US specific.

For me to get more accuracy I switch the GLONASS on.

b.

[Paul L]

Originally Posted by barnakiel

WAAS in Europe?

Where?

Every time I switch the WAAS on, position accuracy decreases.

I thought WAAS is US specific.

For me to get more accuracy I switch the GLONASS on.

b.

WAAS is one of a number of SBAS Sat augmentation systems. Here's a good writeup
SBAS Made Easy | SxblueGPS

[barnakiel]

Originally Posted by Paul L

WAAS is one of a number of SBAS Sat augmentation systems. Here's a good writeup
SBAS Made Easy | SxblueGPS

Fine. Just SBAS does not talk to my Garmin nor to my Samsung and that's about as far as my devices get any improvement over the SBAS.

Or does it?

I will read the source now. Just to make sure my blah is not yet another proof I am behind times!

Thanks for sharing!
b.

[Jim Cate]

Stu and Paul, thanks for bringing up the SBAS in Australia issue. I was unaware of this sort of error, and had been naively switching on that feature in my Vesper AIS. Turned it off, and sure enough, the scattergram developed over 12 hours whilst tied to the dock is noticeably smaller, and the SOG readout is more stable.

Even with SBAS erroneously engaged, the errors were not of significant magnitude, but why not eliminate them? I'm surprised that Vesper does not mention this in their literature... I'll PM Jeff Robins about it.

And a cursory examination of the track recorded by marine traffic shows fewer excursions... essentially all the movements are shown as true N-S displacement There are a very few satellite tracks a few meters to the east, also moving N-S. This may be related to t he resolution of the track plotter in marine traffic's display.

/again, thanks!

Jim

[Dockhead]

Originally Posted by barnakiel

WAAS in Europe?

Where?

Every time I switch the WAAS on, position accuracy decreases.

I thought WAAS is US specific.

For me to get more accuracy I switch the GLONASS on.

b.

The European system is called EGNOS.

It works terrifically well, but only newer GMDSS receivers can use it. It is not the same as WAAS and switching on WAAS will not enable it.

I get sub 2 meter EPO with my main receiver, with both EGNOS and GLONASS going. Soon we'll have Galileo, too!

[StuM]

Originally Posted by Dockhead

The European system is called EGNOS.

It works terrifically well, but only newer GMDSS receivers can use it. It is not the same as WAAS and switching on WAAS will not enable it.

Are you sure about that? Everything I've read indicates all SBAS systems work the same way and if you can use one you can use any that are within range.

A typical quote is this one from the EGNOS site:

https://egnos-portal.gsa.europa.eu/d...gnos/what-sbas

"Several countries have implemented their own satellite-based augmentation system. Europe has the European Geostationary Navigation Overlay Service (EGNOS) which covers the EU and possibly beyond. The USA has its Wide Area Augmentation System (WAAS). Japan is covered by its Multi-functional Satellite Augmentation System (MSAS). India has launched its own SBAS programme named GPS and GEO Augmented Navigation (GAGAN) to cover the Indian subcontinent. Both Korea (2013) and China (2014) have announced plans to start their own SBAS implementation.
All of the systems comply with a common global standard and are therefore all compatible (do not interfere with each other) and interoperable (a user with a standard receiver can benefit from the same level of service and performance whether located in the EGNOS or WAAS coverage area)."

[StuM]

Originally Posted by barnakiel

Fine. Just SBAS does not talk to my Garmin nor to my Samsung and that's about as far as my devices get any improvement over the SBAS.

Or does it?

What Garmin model?

Lots of compatible devices here including plenty of Garmins, many which have been out of production for years.
:
https://egnos-portal.gsa.europa.eu/d.../receiver-list

(But you're right about your Samsung. Few, if any, phones/tablets have SBAS capable chips).

[barnakiel]

Further to my earlier posts, I was misinforming the readers.

I have run extensive 'experiments' today.

Equipment: Garmin handheld, marine grade, chipset 2004.

Accuracy WAAS off: 13 ft
Accuracy WAAS on: 13 ft

Equipment: Samsung phone, newer chipset 2011.

No WASS on the unit (or none advertised)
Accuracy GPS: 8 ft
Accuracy GPS & GLONASS: 6 ft

So my claim that WAAS degrades position accuracy over Europe was dated. It no longer is.

Apparently, NEWER positioning chipset is the shortest track to get improved position accuracy. Activating both networks seem to help another bit too.

Someone can share their view on the newest, fastest and most accurate chipset to look for? The one in Samsung can see Beidou but it is far from new anyways.

b.

[barnakiel]

Originally Posted by Dockhead

The European system is called EGNOS.

It works terrifically well, but only newer GMDSS receivers can use it. It is not the same as WAAS and switching on WAAS will not enable it.

I get sub 2 meter EPO with my main receiver, with both EGNOS and GLONASS going. Soon we'll have Galileo, too!

Yes this is probably the problem with my Garmin handheld. It says 3D differential but it may still be looking for the US based augmentation system, etc.

I will check if Garmin new models have this challenge sorted out. I bet they did.

You can switch Beidou on with your units too (if you are withing Beidou range which is not yet global). I can't say how much this one helps.

We can see Beidou sats from here (Canary Islands).

Cheers,
b.

[DeepFrz]

Barny, how can you tell the accuracy of your phone GPS? What Samsung phone do you have? My Samsung can use an enhanced location but it uses cell towers to enhance the accuracy of the GPS. It very nicely shows me where I am but how can you tell if its within 6 ft.?

[barnakiel]

Originally Posted by DeepFrz

Barny, how can you tell the accuracy of your phone GPS? What Samsung phone do you have? My Samsung can use an enhanced location but it uses cell towers to enhance the accuracy of the GPS. It very nicely shows me where I am but how can you tell if its within 6 ft.?

Accuracy of the Garmin I read from the Garmin interface. The unit is Garmin72.

Accuraccy of the phone I read from any nav App that has a position accuracy field.

I do not use cell towers on this phone as I have removed the card and use this unit as our mini-tablet / gps dongle only. Tested in the bush (off cell range) by far the most accurate GPS we have at this point but I know newer ones are even better.

I can look up the name of the app if you want. Ours is a 'cheapo' 100USD Samsung smartphone and the system is an older Android.

b.