GPS question

[Louis Brandt]

Hello,

I’d like to get a GPS unit for my car, but I have a question. Does the unit have to be mounted in any particular location in the car, in order to receive the signal from the satellite? I was originally under the impression that some part of the unit had to be mounted onto the windshield, but a friend has his sitting in the cup holder between the front seats, and it works fine. Have they made improvements in the units such that they can be mounted almost anywhere?

Thanks,
Louis

[Eric Larsen]

With my unit, once it picks up the GPS signals, it can sit anywhere. SOP is to power on the unit, place it on the dashboard for a couple minutes, then enter the address I'm looking for at a stop light and deposit in a cup holder. First thing I did was change the voice to Joanna Lumley's (Patsy from Absolutely Fabulous.)

[Louis Brandt]

Ok, I understand that it needs to first pick up the satellite signals, but if after it knows where you want to go, you then move it to a place in the vehicle where it can't read the signals, how can it then continue to guide you to your destination?

[Mike Henderson]

Ok, I understand that it needs to first pick up the satellite signals, but if after it knows where you want to go, you then move it to a place in the vehicle where it can't read the signals, how can it then continue to guide you to your destination?
I don't know if I can absolutely answer your question, but some GPS units have sensors in them which measure three axis acceleration. Once you know your starting location, you can get a reasonable estimate of the direction and distance the car travels, which will allow you to keep your navigation.

But that's certainly not as accurate as actually receiving the GPS signals.

Remember, also, that the satellites are usually not directly overhead so you may get an update now and again which allows you to maintain your navigation.

Wikipedia has a good (and long) discussion of how GPS works.

Mike

[Mitchell Andrus]

I've used mine on my lap on battery power. I've also picked up a signal in a shopping mall in a vehicle on display. It showed the car inside the mall right where it was parked.

Depends a lot on the unit, the weather and local emt.
.

[Joe Pelonio]

If i turn mine on in the house, it will never find the satellite. If I take it outside it will find it, but when I bring it back in it loses it. In the car, it will work as long as it's within reach of the windshield, on the console or lap does work, but not in the back seat. I use a heat/AC vent mount so it's on the dash, and it works great there.

[Bob Rufener]

I have a Garmin and it works fine anywhere in the car and in the house. We had problems with ours sticking onto the windshield-fell off a few times as we were driving. We went with a weight dashboard holder. It has a tacky bottom so it won't slip off the dash and we don't have the suction cup marks on the windshield any more. Easy to hide when stopped so the bad guys can't rip it off. I believe that there are several states that it is against the law to have the device suction cupped to the windshield which was another reason to go with the dashboard device.

[Mike Black Milford, MI]

Consumer Reports stated in a review that the Garmin suction cup sometimes lost grip and the suction cup mount dropped the GPS. We have Garmin GPS and we experienced the same problem. Like Bob said, we use a weighted mount that just lays on the dashboard and it has never slid off. It looks like a small bean bag with s smooth inner plate for the suction cup to adhear to. Our Garmin suction cup has never detached from that plate.

[Bill Arnold]

I have a Garmin nuvi260 that works almost anywhere. It takes a little longer to acquire satellites in the house but it still works. In the car, I install it in its bracket on the console just forward of the shift lever so it's easy to see but out of my line-of-sight. It acquires the satellites very quickly and doesn't lose them unless I go into a parking garage or tunnel.

[Chris Kennedy]

We have a Magellan, and we regularly run with it in the console between the seats.

Cheers,

Chris

[Craig Coney]

My Garmin units allow for an external antenna that I place on the dash. I mount my GPS by the cup holder so I can still see it but don't have to look at it all of the time. IIRC, the antennas are $20-30 extra.

[Rod Sheridan]

Same for me, external antenna in the car, built in antenna on the motorcycle.

( I have a Garmin Quest which is waterproof).

Regards, Rod.

[Dennis Peacock]

Same for me, external antenna in the car, built in antenna on the motorcycle.

( I have a Garmin Quest which is waterproof).

Regards, Rod.

OK Rod....I'm jealous now. A GPS on your motorcycle. ;)

My only "on bike" GPS is a willingness to stop at a local store if/when I get lost and can't find my way back. A GPS for my bike is like crazy expensive.

Maybe I need to start dropping bread crumbs so I can find my way back. :D

[Dave Johnson29]

OK Rod....I'm jealous now. A GPS on your motorcycle. ;)


Buy a Goldwing, it is a built in option. :)

[Jim Becker]

Newer GPS devices are more forgiving with placement as they are more receptive to "bounced" signals from one or more of the satellites they are tracking while you are using them. You need to have signal from multiple satellites, three minimum and the more, the merrier. That said, you should really mount the unit while in use where you can see it without taking your eyes off the road in general...and that's why you generally see them on the windshield or if factory installed, high up on the center console. Down in the cup-holder doesn't strike me as the best idea from a safety standpoint... ;)

[Mike Henderson]

It's a common misconception that only three satellites are required to obtain a position. In actuality, four are needed. I've included a quote from the wikipedia article on GPS, but you'd find the same info in any technical description of GPS.

"Three satellites might seem enough to solve for position, since space has three dimensions and a position on the earth's surface can be assumed. However, even a very small clock error multiplied by the very large speed of light[15]—the speed at which satellite signals propagate—results in a large positional error. Therefore receivers use four or more satellites to solve for the receiver's location and time. The very accurately computed time is effectively hidden by most GPS applications, which use only the location. A few specialized GPS applications do however use the time; these include time transfer, traffic signal timing, and synchronization of cell phone base stations."

Mike

[Bill Arnold]

... Down in the cup-holder doesn't strike me as the best idea from a safety standpoint... ;)
I find it safer and less distracting to have my Garmin in its bracket on the console. I set the destination while parked, then take off. The GPS voices distance to next turn, direction of turn and the road name. With a quick glance, I can check mileage to next event much the same as looking to set the AC to a different mode.

[Bill Arnold]

It's a common misconception that only three satellites are required to obtain a position. In actuality, four are needed. ...
Here's what Garmin says about it:
A GPS receiver must be locked on to the signal of at least three satellites to calculate a 2D position (latitude and longitude) and track movement. With four or more satellites in view, the receiver can determine the user's 3D position (latitude, longitude and altitude). Once the user's position has been determined, the GPS unit can calculate other information, such as speed, bearing, track, trip distance, distance to destination, sunrise and sunset time and more.

[Eric Larsen]

Down in the cup-holder doesn't strike me as the best idea from a safety standpoint... ;)

I disagree. Then again, I never look at the screen. I just follow the voice directions.

I found the windshield mounting to be both distracting and annoying. I never use it.

Besides, I have Joanna Lumley telling me, "Now turn around, dahling, and take the second right." Who needs a screen?

[Jim Becker]

Eric and Bill, I do understand your point. That said, given that it's likely difficult for many folks not to look at the map--they are pretty instructive and interesting with POI are involved and there is no copilot available...keeping it closer to where the eyes need to be may be safer in that respect. So I'll modify my own point to say that folks who do tend to watch the GPS screen should consider that when they are deciding on placement in their vehicle.