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Rybren

Survey marker locations

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Has anyone out there been able to find a site that publishes the positions of Canadian survey markers?

 

I thought that it might be interesting to test my GPSr accuracy against a fixed known location such as a survey marker, but I can't seem to find a source for them in Canada.

 

Anyone?

 

Thanks

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Here's a link to Natural Resources Canada Geodetic Survey Division's Canadian Base Network:

http://www.geod.nrcan.gc.ca/site/index_e/products_e/csrs_e/cbn_e/cbn_e.html

It is very good as long as there is a monument in your area. I am lucky enough to have a monument less than 2 km from my house. My GPSr was only 3m off from their position!

 

There are also a few other network monuments listed on the Geodetic Survey page, but are not as dense as this one.

 

If you live in Ontario you can subscribe to COSINE. It will give you coordinates for almost every streetcorner in Southern Ontario! I don';t know how much it costs to subscribe and everyone who looks after it is on strike right now, so you would have to wait for that.

 

Hope there is a fed. monument near you!

 

- Donna G.

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Thanks for the link DonnaG. I found one about 10 km from my house and visited it this morning.

 

My GPS12 could only manage to get within 8 metres with ten minutes of averaging icon_biggrin.gif even though the EPE was around 3 meters.

 

How soon we forget the days of SA and it just goes to show you that the first E in EPE stands for estimated.

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Thanks for the link DonnaG. I found one about 10 km from my house and visited it this morning.

 

My GPS12 could only manage to get within 8 metres with ten minutes of averaging icon_biggrin.gif even though the EPE was around 3 meters.

 

How soon we forget the days of SA and it just goes to show you that the first E in EPE stands for estimated.

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Donna:

 

Thanks for the link. It's exactly what I was looking for. There's a marker about 20km from my place.

 

I guess I know what I'll be doing this weekend.

 

Thanks again icon_biggrin.gif

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Donna:

 

Thanks for the link. It's exactly what I was looking for. There's a marker about 20km from my place.

 

I guess I know what I'll be doing this weekend.

 

Thanks again icon_biggrin.gif

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I had posted a comment regarding my belief that my Venture was working with WAAS and MrGigabyte very rudely informed me that I should know better that being in Toronto I wouldn't get WAAS.

 

Well MrGigabyte I've now got proof that you are wrong. I was curious if those little "D"'s ment anything on the sat display all along.

 

Well I guess they do. I went to This Cacheand got 1.69 m off.

 

This was with 10 sats, waas enabled and little D's on most of the sats in the display.

 

So. I've got no doubt that WAAS DOES work in Toronto. MrGigabyte, thanks for your input. I'll store in the big round file cabinet under my desk with the rest.

 

Rob

Mobile Cache Command

4525_1300.gif

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MrCPU

 

Thank you for your comments .Please remember that the best accuracy you can obtain with your consumer grade GPS is 13m RMS SIS @ 95%. That is 13m Signal In Space. This means half the time you will be 13m to far north, half the time 13m to far south. At some point you unit will display something completely ridiculous like 1.6m.

 

If Garmins programmers chose to display the position to the millimeter, would that make it any more accurate? No, of couse not... but it would sell more units and make more novices believe they can navigate to a greater precision.

 

WAAS is based on ground stations receiving signals and determining clock, orbit and ionosphere errors, then sending those signals back to the WAAS birds. Those birds send the corrections to you, BUT, they are correct for the ground station.

 

Last time I checked, you are in Toronto. To my knowledge, the US has not yet found any reason to place a US ground station in Canada. This does not mean you can not pick up the corrections. It does means your corrections will be completely erroneous (save the the minimal correction for clock and orbit).

 

Also, how does your enabling WAAS make you locating a cache any more accurate if the placer did not utilize the same parameters?

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quote:
Originally posted by MrGigabyte:

MrCPU

 

Thank you for your comments .Please remember that the best accuracy you can obtain with your consumer grade GPS is 13m RMS SIS @ 95%. That is 13m Signal In Space. This means half the time you will be 13m to far north, half the time 13m to far south. At some point you unit will display something completely ridiculous like 1.6m.

 

If Garmins programmers chose to display the position to the millimeter, would that make it any more accurate? No, of couse not... but it would sell more units and make more novices believe they can navigate to a greater precision.

 

WAAS is based on ground stations receiving signals and determining clock, orbit and ionosphere errors, then sending those signals back to the WAAS birds. Those birds send the corrections to you, BUT, they are correct for the ground station.

 

Last time I checked, you are in Toronto. To my knowledge, the US has not yet found any reason to place a US ground station in Canada. This does not mean you can not pick up the corrections. It does means your corrections will be completely erroneous (save the the minimal correction for clock and orbit).

 

Also, how does your enabling WAAS make you locating a cache any more accurate if the placer did not utilize the same parameters?


 

MG,

 

You seem to be quite knowledgable about geography so I'll give you the benefit of the doubt however I find it somewhat odd that I got only a 1.6m error when placing my GPS on this marker. I will be the first to say that it could very well have been good luck. In fact, if it had not have been so windy and I had been alone, I would have taken several readings, turned my GPSr off and back on again etc and noted the coordinates for comparison.

 

As for the WAAS in Canada debate, I've spent considerable time on the Net trying to find any reference to these ground stations you refer to and more specifically their location. On one map I found the circle representing the "range" of the waas system came well up into Ontario.

 

I am not one to dispute facts. I am also not one to take someone elses word for something either. Recently I found a security hole in a piece of software BECAUSE the vendor swore it was secure. I said "Really now! Let me see for myself." (It was the Groupwise 5.5/6 Padlock bug that I found).

 

Anyways, bottom line is this; If you can provide me with some further information regarding your statements on WAAS I'd appreciated, however my so far completely scientifically inaccurate test makes me feel that WAAS does help a lot in my area.

 

As for the last note, the "Cache" in this case was not placed by a cacher. AFAIK the position information supplied to the Geocaching site was transposed from the datasheet for this "benchmark", otherwise I'd be looking at "The sum of all evils" when doing the comparison!

 

Cheers!

 

Rob

Mobile Cache Command

4525_1300.gif

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quote:
Originally posted by MrGigabyte:

 

WAAS is based on ground stations receiving signals and determining clock, orbit and ionosphere errors, then sending those signals back to the WAAS birds. Those birds send the corrections to you, BUT, they are correct for the ground station.

 

Last time I checked, you are in Toronto. To my knowledge, the US has not yet found any reason to place a US ground station in Canada. This does not mean you can not pick up the corrections. It does means your corrections will be completely erroneous (save the the minimal correction for clock and orbit).


 

MrGig, have you ever noticed the distance between WAAS ground stations. It is on the order of several hundred miles. Which implies that you need not be close to a ground station to get useful correction information. The nearest ground station to Toronto is in north central Ohio, not far in the whole scheme of things. The signal from the geostationary WAAS satellite can certainly be received in Toronto since it is further south than many parts of the US that the sat serves. So mrcpu probably was receiving useful WAAS corrections since, to my humble knowledge, the US has no reason to block or otherwise disrupt WAAS signals in Canada.

 

Also MrGig, you could probably get useful WAAS corrections too. There is a WAAS ground station near Seattle and receiving the Pacific WAAS satellite should be no problem.

 

quote:
Also, how does your enabling WAAS make you locating a cache any more accurate if the placer did not utilize the same parameters?

 

The maximum error of two GPSs is the sum of the errors of each. If you can decrease the error of one of them you have a smaller maximum error. If both hider and finder used WAAS, the maximum error would be even smaller. (This is assuming that WAAS gave you a smaller position uncertainty, which is usually the case.)

 

Perhaps MrGig is too busy advertising Geocoins to know what he is talking about.

 

rdw

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quote:
Originally posted by rdw:

Perhaps MrGig is too busy advertising Geocoins to know what he is talking about.

rdw


 

I will assume for the moment that is a joke.

 

If it was not, I ask that you email me directly any concerns you have about my qualifications in the field of Geomatics.

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quote:
Originally posted by mrcpu:

In fact, if it had not have been so windy and I had been alone, I would have taken several readings, turned my GPSr off and back on again etc and noted the coordinates for comparison.


 

This actually will not achieve anything in terms of generating statistically valid data. You need to take many readings over many hours, perhaps days. This is simply based on the geometry of the solution.

 

Working on first order control surveys, we have occupied positions for well over 24 hours while logging thousands of readings. And this is on survey-grade equipment.

 

Regarding WAAS...

 

Here are the current ionosphere correction ground station locations.

 

http://waas.stanford.edu/tmslive/graphics/screen1.gif

 

Reiterating. The total accumulated corrections from valid differentially corrected WAAS data is 7m. The majority of the errors are ionospheric-delay errors. The balance ore clock and orbit.

 

You will receive all the corrections. Orbit and clock will be valid as they relate to the SV's themselves. The ionospheric-delay errors will not be corrected "correctly".

 

Also, a big factor is how the GPSr interprets the recevied corrections. Garmin does not apply any correction adjustment for positions outside the correction area as many other manufacturers do. Also, Garmin receivers do not consider none DGPS signals with ones that are receiving corrections. This inevitably will make the position solution worse.

 

The Canada-wide Differential GPS (CDGPS) Service will eventually overcome the problem but you will need another receiver.

 

http://www.cdgps.com/e/

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