kwolfman

It is selectable on the Garmin Streetpilot III. My wife loves this because she always had to do this with paper maps. :p

OmegaBob

Kewl! Thx guys!

MaRX8

I've had the experince of having a "Handheld GPS System" PDA or Handheld, and one that was installed in a car.
The handheld unit is nice that you can take it out of your car and use it for other things. Geocaching You will find that you don't use it in your car as much as an install system. Why?

Well the screen is usally pretty small, and you'll actually have to stop the car to look at it in most cases. Or if you ever have to input information. Unless you have a passnger with you. If you don't then your going to need a stand, or somthing to mount it to your windshield so you can see it.

You might have wires going all over the place. One for the power, and another for the Antenna if it's not a wireless "Bluetooth" GPS. If it's a stand alone unit that might not be as bad. But then you have the battery / cigeratte lighter cord issue. And you have to make sure it has line of sight for the Satellites. Meaning that it has to be up on your dash or windshield to be effective.

It usally doesn't have voice, and if it does it's usally not loud enough to hear it in the car coming from a tiny speaker. You could get one of those FM transmitters, or a Cassette adaptor to play on your speakers. But the FM transmitter/Cassette adaptor is not going to allow you to listen to your music while driving. Also the cassette adaptor is another cord being strung around. "Can you tell I've done this before?"

My experince has been this, if you get an Handheld GPS system, that's exactly what it becomes sitting on your desk/table. You may use it for a month, and use it for those long road trips. But after awhile it's just a hassle setting it up, and taking it down inside your car. Or having to put new batteries in it, because you left it on and they went dead.

If it's built into your car, it's always there, ready to go. Especially if you need it just to find the address of a meeting, party, hotel or resturant. True you probably won't use it everyday, but it certianly handy when it right there ready to go.

You'll never regret getting the installed NAV system. It's just hard paying for it.

8_wannabe

Awesome comments, MaRX8. Thanks. You're the only one I've seen so far that has used both handheld and built-in's so your comparison is appreciated. You validated all my suspicions about convenience or lack thereof of the handheld. Do you also have any thoughts about the technical issues in my post above, such as built-in works in tunnels thanks to gyro vs handheld having to recompute position when line-of-sight is restored. Also, the accuracy issue of one antenna on handheld vs 2 antenna on built-in offering greater accuracy. Did you ever notice either of these phenomena?

MaRX8

Going thru a tunnel is usually not a big deal for a NAV unit. Because it instantly updates your position, once you've restored line-of sight again. A system that uses a gyro unit, can certainly help with this, but I've haven't used one that does have a gyro in it. That's something thats fairly new.

Also about 3 years ago, the government made it so that commercial GPS units where more precise. There use to be a delay or an offset of the GPS signals being transmitted. This was done for security reasons. Only Government GPS units had a special device to correct this signal flaw. So your accuracy was not as precise as it is today.
"Intentional degradation of the satellite signal — Selective Availability (SA) is an intentional degradation of the signal once imposed by the U.S. Department of Defence. SA was intended to prevent military adversaries from using the highly accurate GPS signals. The government turned off SA in May 2000, which significantly improved the accuracy of civilian GPS receivers."

Since commerical airliners started to migrate to GPS units. There was a request to remove this delay/offset. When they finally removed the delay/offset, everyone's GPS unit got an automatic upgrade in a way. It was more precise.

The Nav unit calculates your elevation, and speed biased on the triangulation of the Satellites. Your Nav unit needs at least three satellites to determine your 2-D position, if you add a forth it can tell you where you are 3-D, meaning your elevation. I'm not up to date on the latest and greatest, but my car unit would track up to 8 satellites, which was pretty good the more satellites it's tracking the more precise the system will be. Newer units track around 12. With there being about 29 sats operational. Half of those are on the other side of the earth at any given time. You would have to have a clear 360 degree view of the horizon and sky for your GPS unit to pick all 12 up. But you only need 3 for pretty accurate information. GPS isn't like Satellite radio, where you get drop outs every once in awhile usually from tall building or canyons. With 29 Satellites in the sky, there are always a few that it can see.

Most unit's only have 1 GPS antenna. Where that antenna is mounted is the biggest factor. The top of the roof is the best place. Or somewhere near your rear window glass. Or where the rear view mirror is a good place also.
I guess some Navigation units might have more than 1 antenna, but the only reason to have 2 would to get a better view of the sky, and if your car was at a stand still, and you needed to know what direction it was facing because it was on a turntable. If your at a stand still, a single antenna GPS unit can't tell you what direction your facing, unless your moving, and it only thinks your facing that direction because your moving that way. Two antennas would allow the unit to know which way it's truly facing.

So here's another thing about Install vs. Handeld. Powering up the unit. Depending on how fast the processor is in the device. It has to take a few minute to align it's self (Find and track the Satellites in the sky). This can be a few seconds to a few minutes. 10 mins is the longest I've seen it take to align a GPS unit. Once it's found 3 satellites in the sky, it can usually find the others quickly. So unless you have some type of power to the unit at all times. It has to re-sync it's self with the sky. Car units usually get this power from the cars battery, or a sub battery that recharges when the car is running. So it's always aligned to the Satellite in the sky. Some unit's just have such a fast processor that it just finds that satellites that fast.

Hope this helps, I'm not sure of the specifics of the RX-8 unit. But I ordered one because, I know what it's like to have a handheld unit. Handheld units are great, for your Hand and outside. Not that great for your car.