garmin streetpilot c580 map update 2008, part 2

I applied my City Navigator NT 2008 map update to my Garmin StreetPilot c580 two days ago and I noticed a little boo-boo in the system.

This boo-boo is only able to be recreated under a very specific set of circumstances.

1. The GPS mode is set to WAAS/EGNOS instead of Normal.
2. You are traveling on a road that veers slightly to the left or right.

You're navigating a route. You approach a four-way intersection and the StreetPilot tells you to turn left. However it's not a true left turn. The road veers slightly to the left or right and the StreetPilot "thinks" this is supposed to be a turn. When you look at the on-screen map, you can plainly see you're supposed to stay on the road you're on, but the arrow "squiggles" a little bit because of the slight veer in the road, then straightens out after the squiggle informing you that you shouldn't turn.

After thinking about it, I thought to myself "This must be the WAAS doing this... maybe it's working too well?"

I set the StreetPilot back to "Normal" GPS mode and now it navigates like it's supposed to.

Earlier today I called Garmin to alert them of this. Most people understand that when driving with GPS navigation you need to exercise common sense and not always take the system's instructions as gospel, but there may be a few that blindly follow whatever the unit says and not give it a second thought.

I was informed that what I reported will be sent to cartography (the Garmin programmers,) and this may end up as a firmware update in the future.

If you want to make sure all the proper updates are applied to your StreetPilot, download the Web Updater, install it, launch it and plug your GPS via USB into your computer when prompted. The software will update whatever needs to be updated in your StreetPilot.

. . .

Some questions answered:

Why do you use WAAS instead of Normal mode?

Because it has better accuracy. Normal mode usually has a resolution of roughly 50 to 325 feet. WAAS mode increases the resolution to be as "tight" as 10 feet.

In layman's terms: Normal mode will place you accurately to about 100 feet or less of your destination. WAAS places you accurately within 10 feet or less of your destination.

If you do mostly residential in-town and highway driving, you do not need to enable WAAS.

If you do a lot of metro in-city driving, WAAS can help.

To note: I encountered the boo-boo with the latest map update because the WAAS was actually working too well.

Are there any disadvantages to using WAAS on a StreetPilot?

It's a battery sucker. If you're operating a StreetPilot on battery power with WAAS enabled, this decreases the battery life significantly. This is because the StreetPilot has to "think" more to provide navigation routes. More computer "thinking" = more power needed = less battery life.

Other than that there aren't any disadvantages.

Why doesn't the StreetPilot come out-of-box with WAAS enabled?

Because most people don't need it. However the option is there so if you want to try it out, go ahead. It won't cost you anything.

Will I notice a big difference in the way my StreetPilot navigates with WAAS enabled?

Some will and others won't. If you find your StreetPilot gets "confused" at certain places, such as "Y" intersections, entrance/exit ramps and so on, WAAS may be the cure you're looking for. But if you're not experiencing any of that, there's no reason to enable WAAS other than the just-because-you-can factor. 😀