Waas In Mexico

[+Geosophers]

Just wondering if anyone knows how WAAS reception is in mexico. I understand that the 2 WAAS satellites are geostationary and therefore orbit over the equator. Considering this, it seems to me that WAAS reception should be better in Mexico than in Canada for instance.

[+PDOP's]

What you said makes sense as the satellites should be higher in the sky. There's still the question of distance from a ground reference station and it's effect on the accuracy of the corrections.

[Kerry.]

One needs to differentiate bewteen WAAS reception and WAAS corrections. WASS reception might be good but without valid correction data the whole thing fails. Most recent software upgrades now direct the receiver to ignore received WAAS signals if outside the valid ground footprint as far as being valid correction data is concerned.

 

Cheers, Kerry.

[+PDOP's]

Most recent software upgrades now direct the receiver to ignore received WAAS signals if outside the valid ground footprint as far as being valid correction data is concerned.

 

Kerry

 

Any idea what they're using as a model for this footprint? I'm at least 500 km from the nearest ground refernce station and I can get WAAS fixes that are within a couple of metres of a known benchmark.

Edited November 25, 2003 by PDOP's

[Kerry.]

PDOP, have no idea how it's defined or how they might define it in the receiver, but it would probably be tied to the grid point data (maybe?) as transmitted and therefore might be a function of (based on/from) the actual system? Might even look into this one a bit further.

 

There's probably a little more to all this than simply distance as there must also be a certain number of common satellites in view from a number of ground stations (regardless of distance) as well as thr user.

 

Cheers, Kerry.

[+PDOP's]

... it seems to me that WAAS reception should be better in Mexico than in Canada for instance.

I just found this link again which would seem to indicate that WAAS corrections may not be as valid in Mexico. This shows a type of vertical accuracy and horizontal accuracy should be twice as good (half the error)

[+Geosophers]

Thanks for the link PDOP. It does look like WAAS isn't available in Mexico doesn't it. From that map, it appears that British Columbia (my home) should have excellent reception. However, from experience I can say that is not the case. I need an absolutly unobstucted view of the southern sky to get a lock and sometimes it still doesn't seem to be enough. I this case it probably has more to do with how low the WAAS satellites are in the sky instead of distance from a ground station.

[+PDOP's]

... it appears that British Columbia (my home) should have excellent reception. However, from experience I can say that is not the case. I need an absolutly unobstucted view of the southern sky to get a lock and sometimes it still doesn't seem to be enough. I this case it probably has more to do with how low the WAAS satellites are in the sky instead of distance from a ground station.

I agree with what you're saying. For WAAS to be useful you have to be able to receive the signals ( a good view to the south ) and the corrections in the signal have to be valid ( within some undefined distance of a ground reference station ).

 

I'm in Alberta at 53.4º latitude and I have to have a clear view to the south to receive signals. It's absolutely useless in the bush.

 

For more on Canadain experiences with WAAS have a look at this thread.