Is navigation antenna directional???

[Even Steven]

I had to remove my OEM Toyota navigation system today to do some work to my 4Runner, and I was surprised to see that my navigation antenna had moved from the location that I installed it. Actually, it wasn't even level....it had fallen off its mounting location and landed sideways between the head unit and the ventilation tube.

So that go me thinking.....since my navigation system was still working properly and tracking correctly, does that mean the antenna is not directional? Can I mount it in any direction and still expect it to track properly? Does it rely on triangulation to determine direction/heading?

 

[A/V1]

GPS signals use a time stamp which your receiver reads and determines where you are based on the time stamps from four different GPS satellites (for your triangulation). So if you mean directional - by it should be mounted with one side facing front, another facing rearward, then no, it is not directional. For best reception, it should have a clear line-of-sight with the sky (& satellites), and should be mounted horizontally on a piece of metal, to form a plane.
The fact that you found it sideways and were still apparently getting a good signal says a lot. You must be in a good area for sat reception.

Check this out...


GPS info

 

[Even Steven]

Thanks for the info and the link. I thought it was pretty cool that my navi was still tracking properly, even though the antenna was basically sitting sideways in the dash.... I live in the metro NY area, so I guess the satellite reception is pretty good here....

 

[LimitedT4R]

Follow-up GPS question

Hey Guys, where is the GPS antenna typically located on a T4R? My 04 T4R was totalled by a kid that didn't like the looks of the front end, so I just bought an 06 T4R with nav.

Something is screwy on it though - I can drive about 2 miles and it ends up being about .25 miles off actual location. The dealer changed the tires on it to the same size as recommended, and I've repeatedly modified location and updated tire change selections under setup - with no luck.

Any help and direction would be greatly appreciated! Thanks for the help!!

 

[Even Steven]

I believe the location of the GPS antenna is under the dash, behind the head unit. But if you're getting a GPS signal, I doubt the antenna is the problem.

How are you determining that your 4Runner is 1/4 mile off after driving two miles? Does it correct itself when it receives a signal from the satellites?

BTW, I've read that the tire calibration must be performed by driving at least 6 miles after hitting the calibration button. This information was not found in the Toyota navigation manual, but in an Eclipse navigation manual. Since the OEM navigation is made by Eclipse, I'd guess the same rules apply.

 

[LimitedT4R]

GPS alignment

Thank you for the information Even Steven!

The manual states if you have a "GPS" icon under the direction and scale icons - it means you're receiving a signal. I rarely see "GPS" - but I read a thread last night that said the unit does not receive a constant signal but computes where you are then makes corrections occasionally. So I guess I shouldn't expect it to work like my handheld Garmin eTrex?

I determined my unit was 1/2 mile off when I did a manual alignment 2 miles away from my house at an intersection identified on the map. I then drove home, parked in the driveway and entered a destination from the indicated location to home. The nav unit said it was 1/2 mile away to the west - yet i was sitting in the same location as I was when I manually entered my home location. It did not correct itself, and remained that way even after I stopped the engine and restarted later.

Thanks a million on the 6 mile requirement - I definately did not know that and will give it a try!

Thanks again!

 

[Even Steven]

Okay, but you should be seeing the GPS icon almost constantly, as long as you're not driving in a tunnel or another low-reception situation. My navigation almost always shows the icon...

As far as the signal goes, I believe it works like this:

The system does receive constant GPS signals, but it doesn't rely on them to constantly track vehicle movement. Instead, the vehicle speed sensor and an internal gyro do most of the vehicle tracking, with the satellite signal making occasional corrections. That's why you'll sometimes see a small correction in vehicle location on the screen. And if you're driving in an area with two close parallel roads, you might even notice your vehicle track for a few moments on the wrong road, but the navigation system will eventually correct itself and put you back on the correct road.

Handheld navigation units rely on satellite signals alone to track location, so I guess they behave a little differently. I'm guessing that you may have a problem with reception if you don't see the GPS icon almost continuously.

 

[LimitedT4R]

Thanks again!

I really don't have an issue with tall buildings, etc., here in Southern Maryland - you can't get more rural / flat farm land than what we have here.

My 06 Avalon nav has never had a problem - this one has me scratching my head. Guess I'll take my wife on a ride this afternoon and maybe time the amount of the trip the "GPS" icon is on? My concern is I just bought this vehicle - its certified so if the tire calibration doesn't fix the problem I guess I need to get it back to the dealer.

Thanks Even!!
R/LT4R

 

[LimitedT4R]

Nav update

Update on the nav - after driving about 20 miles without seeing a "GPS" icon under the heading and scale settings, i was 12.6 miles off accuracy.

Could someone please tell me how I can get to the head of the nav system to see if the antenna is installed correctly?

Thank you.