WASS/EGNOS - Enable or not?

Do a search on POI Factory for WAAS. Here are just a few threads:
http://www.poi-factory.com/node/6864
http://www.poi-factory.com/node/2199
http://www.poi-factory.com/node/7957
http://www.poi-factory.com/node/5698

RT

Short Answer: OFF

I keep mine all the time but there are other opinions but read this thread then make your decision http://www8.garmin.com/aboutGPS/waas.html

I had mine turned on since I received the unit however I just turned it off and guess what, it takes less time now to acquire satellites! I'll see how much longer the battery last now that I've turned it off because I know for a fact with it on my batteries lasted no where near the 3 hours they say they will in the manual.

IMO, turn it off. Kills battery and I dont get any better reception.

charlesd45 wrote:
I keep mine all the time . . .

I keep it on all the time.Never use the battery power only used when attached to cig lighter or the computer usb.I get good signal and no problem when I first turn it on picking up satellites.I would think if it was a part of the unit it serves a purpose and based on the information furnished about it I see no reason to not take advantage of the feature.

Faster battery drain, sometimes worse accurracy, longer satellite access time, and a built-in display error of 88* feet at 60 mph that negates any added accurracy that 'might' occur, just to name a few.

RT

* Mobile applications: Many GPS units update their display every second. Is this period of time, at 60 mph, you travel approximately 88 ft, which means the display is off by 88 ft just prior to display update.

Re the 88 ft discrepancy between the displayed position and actual. To relate that to accuracy is very misleading; it is merely a delay. It will accurately show you where you have been. True inaccuracy makes it difficult for the unit to snap your position to the streets or distinguish between two parallel streets. Totally different things.

That being said, I think I will henceforth turn that feature off when operating on battery.

Although I referred to the 88 feet as 'display error', it still relates to total accurracy of the GPS unit. When moving at 60 MPH, even if one had WAAS accurracy of 0 feet, recording the displayed location just prior to the display update will result in the recorded information being off by 88 feet. When testing accurracy of aircraft equipment, we recorded what the pilot saw ... not what the unit was capable of producing without taking into account the display error. It would be a completely different matter if our GPS units would update every 10 milliseconds.

RT

I leave mine off as well. I tried it on and off - didn't get any better reception, accuracy, and killed my battery quicker.

I always keep my NUVI 350 WAAS turned off

It's WAAS, not WASS, and I have no idea what WAGG refers to.

I have had GPSs with and without WAAS. It's an error correction signal sent by geo-sync satellite. The error correction covers a fairly large area, but should be localized enough to be of help. Error correction helps the gps correct for variables in signal propagation through different atmospheric temperatures and pressures and the like (the speed of light is a constant in a vacuum but not in the Earth's atmosphere). I have never seen a case where not having WAAS gave better results than having WAAS, and from experience I find it hard to believe that in the USA the error correction signal ever actually makes things worse than better. If you are more than 500 miles from a point in the US that is being monitored then using the WAAS signal may indeed reduce your accuracy so it should be disabled if you are in Europe, Asia, Australia, Africa, South America or Northern Canada or Southern Mexico. True, it is mainly used for things like aircraft that need greater accuracy, but personally I feel that I "need" all of the accuracy that I can get, even in a nuvi intended for on-road use with "road lock". I wish that my 250 had WAAS support, but it apparently does not.

I leave the WAAS turned on in my 650.

I leave mine on all the time. I fly a lot so in flight performance is also important to me. I find that the ability of the unit to lock on and maintain accuracy under various conditions while in flight is a lot better with it on. I don't see much difference on the ground. For battery life, I find the screen brightness has a lot more effect than anything else.

I have read that if your unit has SIRF, it is more accurate than WASS and you should disable WASS. Maybe try an internet search WASS vs SIRF.
Jon

SiRF is a chip set for processing GPS signals while WAAS is an error correction signal to reduce the amount of positional difference between the L1 and L2 signals sent from the satellites. SiRF chip sets for the commercial PND marketplace usually incorporate WAAS.