WAAS in Canada

[+Olar]

It was suggested in a recent post that we start a topic thread in this Canada forum where we cachers can report on our WAAS performance findings. The main reason is to determine availability in various parts of Canada and its effectiveness.

 

In case you have not seen the WAAS coverage map provided by EraSeek you may view it in this recent topic posting.

 

I'll start by reporting my midmorning visit today to a geodetic survey marker in northwest Toronto with published coordinates: N43°43.5977666, W079°36.57717

 

No WAAS: after ten minutes my GPS V read N_.599, W_.576 which translates to an accuracy of 2.772 metres.

 

With WAAS: after ten minutes with same birds plus sat. number 35, N_.598, W_.578 for an accuracy of 1.195 metres.

 

I was getting a good strong lock on all 10 visible satellites from this location and all showed a differential signal reception when WAAS was enabled and sat 35 popped-up.

 

Cheers, Olar

 

"You are only young once but you can stay immature forever"

[+PDOP's]

Bump You can use GeoCalc a great little piece of freeware written by a cacher FizzyMagic to calculate the distance between two points. This will tell you exactly how far off your waypoint is from a benchmark. GeoCalc can be downloaded at this web page.

 

PDOP's GPS Pages

[Boromir]

I went to one of the Canadian Base Network monuments on the weekend with my Magellan Meridian Gold GPSr. With the GPSr on the monument before the WAAS fix it reported I was 3m away. Once I started WAAS correction it dropped to 2m, then after a minute or two of averaging it dropped to 1m. I recorded a waypoint at that location and used the GeoCalc software. The final horizontal error was 0.925m, which is consistent with the 1m offset reported by the GPS. Elevation error was also low at around 1.168m.

 

Of course with my GPSr rounding to 3 decimal places the calculated value of 0.925m could be out by a fair bit. If I did my math right rounding to 3 decimal minutes means the actual point (at that latitude) could be anywhere in a rectangle around the given point where the rectangle is about 1.12m wide (E-W) and 1.85m high (N-S). Now depending where the GPSr was in this rectangle the following results are possible for the offset:

Center: 0.925m

Best Case: 0.340m

Worst Case: 1.863m

So therefore the GPS was no more than 1.863m out (most likely much less than that) with the WAAS correction, which is really not bad at all.

 

It is probably also worth noting that the known/published waypoint entered in the GPSr was out by 0.331 m because of the same rounding problem, which only needs to be considered when looking at the offset of 1-3m reported by the GPSr when navigating to the marker. It does not effect the calculations above since I used only use the non-rounded published location and the final coordinates returned by the GPSr.

 

Rounding of elevation to the nearest meter throws the vertical error out a bit as well, basically somewhere between 0.668m and 1.667m assuming that the rounding is to the nearest meter, not always up or always down.

 

Yes, I have taken a couple too many applied science courses.

 

The actual numbers used were:

 

Station Number: 89X005

Name: PIER E

Location: Near Gainford Alberta

 

Published Location:

N53° 35' 57.6518" (Rounded to N53° 35.961' for the GPSr waypoint)

W114° 43' 13.6684" (Rounded to W114° 43.228' for the GPSr waypoint)

791.832 m

 

GPS Reading (With WAAS, averaged for a couple minutes)

N53° 35.961'

W114° 43.227'

793m

 

Note: Corrected vertical data 03-09-29

 

[This message was edited by Boromir on September 29, 2003 at 09:07 PM.]

[+PDOP's]

Boromir

 

Any thoughts on the 19.5m error in elevation? I had thought that a GPS fix was half as accurate in the vertical (error would be twice as in the horizontal).

 

PDOP's GPS Pages

[Boromir]

quote:

---

Originally posted by PDOP's:

Boromir

 

Any thoughts on the 19.5m error in elevation? I had thought that a GPS fix was half as accurate in the vertical (error would be twice as in the horizontal).

 

http://members.shaw.ca/pdops/

---

 

User problem, recorded the wrong value off the form, correcting my previous posts. Vertical was around 1m out.

[+PDOP's]

Took my recently acquired GPS76 out to a Canadian Base Network monument this morning. The CBN is on a rise with a clear view to the south so I was able to get a lock on the WAAS birds for the first time. After letting it sit for 10 minutes I had the following results:

 

With WAAS (both sat 35 & 47, and D showing for all sats) and an indicated accuracy of 2.6 metres: 0.911 metres horizontal and < 1 metre vertical

 

Without WAAS with an indicated accuracy of 5.4 metres: 3.032 metres horizontal and 2 metres vertical

 

PDOP's GPS Pages

[jan27jay]

Being somewhat new to caching, I have two questions that may sound very basic and dumb.

 

1. What is WAAS?

 

2. Where do you find a list of published survey markers in Canada?

 

________________________________

Jay Millington

Millington Photography

Weddings and Portraits

905-895-2544

[+PDOP's]

quote:

---

Originally posted by Jay Millington:

Being somewhat new to caching, I have two questions that may sound very basic and dumb.

 

1. What is WAAS?

---

 

Wide Area Augmentation System. Have a look at this web page

quote:

---

2. Where do you find a list of published survey markers in Canada?

---

 

Have a look at this

thread.

 

PDOP's GPS Pages

[+PDOP's]

Took my GPS76 out to Canadian Base Network station A351148 again. The CBN is on a rise with a clear view to the south so I was able to get a lock on the WAAS birds easily.

 

Today I had the following results:

 

With WAAS (both sat 35 & 47, and D showing for all sats)my best result was with an indicated accuracy of 2.8 metres:

 

0.907 metres horizontal and < 4 metres vertical

 

Without WAAS with an indicated accuracy of 2.4 metres:

 

0.636 metres horizontal and 2 metres vertical

 

I'm not sure why the non WAAS results are better. I did take the WAAS readings first and the non WAAS imediately afterwards so perhaps the WAAS correction were still being applied within that short time frame.

 

PDOP's GPS Pages

[+Hard Oiler]

Finally found a first order benchmark with reliable coordinates close to home and checked out my Meri Gold. On two visits it was within 1 metre both horizontal and vertical with WAAS enabled (haven't tried with WAAS off as it's not easy on a Meridian). Was so impressed I turned it into a Calibration Cache.

 

One question I had was what vertical datum the Meridian uses. The benchmark is quoted as being CGVD28 which I think is close to NAVD88 around here but I thought GPS measures ellipsoid height which can be significantly different. So is the GPS receiver doing a conversion and if so to what? Anyone know or know a web-site that explains how vertical datums work and what the differences are?

[Geoslackers]

I'm on Vancouver Island and use an etrex legend. I seem to be able to lock onto WAAS every once in a while but really not often enough to make it worth while. If there are any obstructions you can forget it. The best accuracy I've gotten with WAAS is 4m. I'm sure this has more to do with my unit that anything else. Without WASS I can get 5m about 90% at the time.

[+Capitalpete]

I'm on Vancouver Island and use an etrex legend. I seem to be able to lock onto WAAS every once in a while but really not often enough to make it worth while. If there are any obstructions you can forget it. The best accuracy I've gotten with WAAS is 4m

 

Try taking your legend out on the break water in the inner harbour to see just how accurate the WAAS feature is when you get a clear shot of the satellite. Walk out to the end with the WAAS off, check the accuracy, then use it with the WAAS on. I was able to get under 1M with a 76MAPS, so I am sure yours will not be far off. I will take a Legend out there just as soon as I get another one, just to compare them. I have used a Vista quite a bit, and found it to be quite accurate with the WAAS on, but you do need a clear overhead view to get it.

 

While you are out there, check out the great cache that is somewhere out there!

[+RobertM]

I may be wrong, but I think a lot of people confuse WAAS with the Differential signal. In Richmond near the Vancouver airport they transmit a "fixed/adjusted" signal. If you pick up this signal your accuracy will improve. A lot of people think they are getting a WAAS signal near the airport when infact it's an adjusted differential signal. (You can do a search on the internet government of Canada websites to determine where these signals are transmitted from.)

 

To check if you are receiving WAAS check which satellites you are picking up. I can't remember the exact numbers off-hand, but I'm sure someone knows them. Only if you are picking up one of the WAAS satellites will you be getting a WAAS signal.

 

With a Differential signal you can get very good accuracy. In Victoria I got 2m accuracy on the south point (not sure what the area is called), that was with a Garmin Legend (patch antenna). Out caching in Port Coquitlam once with my GPS V I picked up a differential signal from Richmond and was getting 4m accuracy (with a quad helix antenna).

 

My 2c. ;-)

[+PDOP's]

I may be wrong, but I think a lot of people confuse WAAS with the Differential signal.  In Richmond near the Vancouver airport they transmit a "fixed/adjusted" signal.  If you pick up this signal your accuracy will improve.  A lot of people think they are getting a WAAS signal near the airport when infact it's an adjusted differential signal.  (You can do a search on the internet government of Canada websites to determine where these signals are transmitted from.)

 

You would need a separate beacon receiver linked to your GPSr to take advantage of the differential corrections transmitted by the coast guard in Canada.

[+RobertM]

I may be wrong, but I think a lot of people confuse WAAS with the Differential signal.  In Richmond near the Vancouver airport they transmit a "fixed/adjusted" signal.  If you pick up this signal your accuracy will improve.  A lot of people think they are getting a WAAS signal near the airport when infact it's an adjusted differential signal.  (You can do a search on the internet government of Canada websites to determine where these signals are transmitted from.)

 

You would need a separate beacon receiver linked to your GPSr to take advantage of the differential corrections transmitted by the coast guard in Canada.

I pick it up on my GPS V and the accuracy increases. I don't need any special things to make it work. The GPS says it's receiving a 3D differential signal.

[+PDOP's]

I pick it up on my GPS V and the accuracy increases. I don't need any special things to make it work. The GPS says it's receiving a 3D differential signal.

Then you are receiving the WAAS signals. WAAS is a form of differential GPS which is why your GPSr shows it's receiving a 3D differential signal.

[+Geosophers]

Is there some sort of attachment you can get for the etrex legend to recieve DGPS. It would be great because I know there's a transmitter close by .

[Goldguru]

In order to recieve differential gps signals you are required to have a DGPS Radio beacon receiver and seperatate loran-C (or equivilant) antenna.TWR has been experimenting with this setup for several months but it appears limited to vehicle use,due to the nessasary ground plane requirement of the said antenna.The transmitted beacon is an approx 20m~ long wave.however 10km +\- of Richmond a smaller antenna may suffice..I believe while testing mobile our best hdop was in the order of .92m. using a CSI ABX-1 DGPS beacon reciever locked onto Amphtrite Pt.....Gg

[+PDOP's]

Is there some sort of attachment you can get for the etrex legend to recieve DGPS. It would be great because I know there's a transmitter close by .

Yes but it's not cheap. Have a look at this site for prices. It also has some good information on WAAS vs DGPS and the coverage of the coast guard beacon system.

 

You could also try this homebrew receiver.

Edited December 2, 2003 by PDOP's

[+Geosophers]

Is there some sort of attachment you can get for the etrex legend to recieve DGPS. It would be great because I know there's a transmitter close by .

Yes but it's not cheap. Have a look at this site for prices. It also has some good information on WAAS vs DGPS and the coverage of the coast guard beacon system.

 

You could also try this homebrew receiver.

Thanks for the links. Mucho expensive. I think I'll cross that off my christmas wish list as I know my girlfriend would laught at me. The homebrew receiver is very interesting. While it states that it does very little for consumer type GPS devices, it would be a fun project to do. I may try to incorporate this in my school electronics project coming up in January.

Edited December 2, 2003 by Geosophers

[+PDOP's]

Looks like there might be some progress in expanding WAAS service in Canada.

From the FAA's SatNav News, June 2003

        WAAS Program Manager Dan Hanlon, WAAS Technical Manager

        Leo Eldredge, and WAAS System Engineer Jeff Auerbach, met with

        Canadian Officials in April 2003. The FAA and Canadian officials

        drafted an agreement calling for the placement of up to four WRS

        sites within Canada, which would expand WAAS service across most

        of Canada. By adding WRS sites in Canada, the FAA also improves

        WAAS coverage and service levels across the northern U.S.,

        particularly in New England.....WAAS service

        extension to Mexico and Canada is expected to be complete by

        2005.

 

The map in this article is hard to make out but it looks like it shows WAAS Ground Reference Stations in Winnipeg, Newfoundland and Labrador.

[+Hard Oiler]

By adding WRS sites in Canada, the FAA also improves        WAAS coverage and service levels across the northern U.S.,  particularly in New England.....WAAS service extension to Mexico and Canada is expected to be complete by 2005

Interestingly I'm currently in Northern New Brunswick on the Maine border and getting a very good WAAS signal. EPE at 3 metres in the bush with lots of snow on the trees - much better than a recent trip to the UK where I never did get WAAS (or the European equivalent EGNOS) and even saw EPE's over 100 metres in downtown London.

[+Couparangus]

For what its worth my GPS drops to about 6ft of accuracy when a WAAS bird is within view. This compares with about 11ft without - both readings on a good day. I have to wonder just how accurate this is though. I work with digital microwave and there's always a certain amount of diffraction through differing temperature (and density) air masses. There is also diffraction of signal over hilltops, buildings and such. These introduce delay and jitter. This is not to mention some of the truly bizarre effects aurora-B has on radio signals. The polarization of GPS signals is circular so reflected signals are largely ignored (except for those which are reflected twice, a la between two buildings) I'm no GPS expert (its a science unto itself) and I do know there's a lot of "error-correction" built into receivers, however logic tells me that a GPS is never as "close" to the target as it thinks it is. And I say this not as a justification for my failed geocache finds!

 

Cheers!

Coupar-Angus

[+PDOP's]

Back on topic - a couple more waypoints collected on known benchmarks with WAAS.

 

Took my GPS76 out to Canadian Base Network station A351148 again. The CBN is on a rise with a clear view to the south so I was able to get a lock on the WAAS birds easily. Also visited an Alberta Survey Control benchmark nearby

 

These are my best results from several waypoints taken.

 

First Benchmark:

 

WAAS sats 35 & 47, 9 regular sats with D showing for all sats my best result was with an indicated accuracy of 2.8 metres:

 

2.2 metres horizontal and < 2 metres vertical

 

Second Benchmark:

 

WAAS sats 35 , 8 regular sats with D showing for all sats my best result was with an indicated accuracy of 3.7 metres:

 

0.0 metres horizontal and < 1 metres vertical

 

Errors ranged up to 4.3 metres horizontal and < 4 metres vertical with a total of 7 waypoints collected.

 

I've put a page up about WAAS on my site.

[+PDOP's]

An update from Nav Canada

 

We're on the verge of signing an agreement with the FAA covering the installation and operation of WAAS stations at Winnipeg, Goose Bay, Gander and Iqaluit.  With the current stations in the lower 48 and Alaska, WAAS could serve most of the western provinces, southern Ontario and a small area in south-western Quebec.  The addition of 4 stations will extend coverage to the eastern provinces to about 55N latitude.  The addition of more stations in Alaska will extend coverage into the Yukon and western part of the NorthWest Territories.  The aim is to have the stations operational by the end of 2005.

[+PDOP's]

Took my GPS76 out to another survey benchmark by one of my caches. The Alberta Survey Control benchmark was at the top of a hill by a fire lookout with a clear view to the south so I was able to get a lock on the WAAS birds easily.

 

These are my best results from several waypoints taken.

 

WAAS sats 35 & 47, 10 regular sats with D showing for all sats my best result was with an indicated accuracy of 2.9 metres:

 

1.9 metres horizontal and < 4 metres vertical

 

Of the three waypoints I collected the maximium errors were only 3.0 metres horizontal and 4 metres vertical.

 

My page on WAAS in Canada.

Edited January 30, 2004 by PDOP's

[+xTerraCacher]

I was a member of Auxiliary Coast Guard Unit 29 out of Ladysmith BC, and on our Zodiac Hurricane 733 we had a Sitex GPS unit with differential. A separate antenna was required, and the differential signal is transmitted from Point Grey (Vancouver). We commonly (on the water, so *no* obstructions) had accuracy within 1 - 2 feet. Although always keeping a lookout while underway, we learned to trust our instruments to the point of doing high-speed (40 mph) emergency runs through Porlier Pass in the middle of the night in the rain. (not recommended unless life/death situation ). Although my eTrex Venture is pretty accurate, it's always been my personal opinion that WAAS is a "poor mans" differential, and serves most applications very nicely.