TomTom accuracy?

[avg1joe]

I have a tomtom ease gps in my car. I'm trying to compare the satellite maps of my property lines with real world landmarks. I can click on the corner of my property on the computer and get long. and lat. coordinates. My gps will display long. and lat. coordinates. Anyone know how accurate these car gps units are off road? In other words how accurate are they, to within how many feet?

 

[mdram]

should be within 10 feet

 

[navychop]

15 meters, unless WAAS is also used, then 3 meters, per this.

 

[Ilya]

I think the accuracy actually depends on how many satellites your GPS is seeing.

 

[berck]

It also depends on your actual location because of atmospheric issues. GPS accuracy is poorer in Alaska than it is in the continental US. I can't find them now, but (I believe) the FAA does accuracy studies at certain locations around the world. The ones I saw were showing the differences between when SA was being used, and when it turned off. Anyway, high Latitudinal spots still showed a lot of inaccuracy.

 

[navychop]

I think those accuracy maps have been "disappeared." I know some GPS related pages I referenced before aren't there anymore.

Yes- I believe you need to see at least 4 satellites. But your unit might not use all that are available. Physical location, including altitude, matter, as well as other factors. Plus, GPS is suppressed in certain areas, by physical means and/or requiring blank spaces in the software/database. For example, one place where this happens is [CENSORED]

 

[TheForce]

Two issues- accuracy and resolution. It is true that accuracy can increase as well as features based on the number of sat signals, but also resolution defines how fine you can get with the map device's ability to zoom in. Then we have response and updating which is part of the resolution story. Number of satellites you can add features like speed and elevation.

 

[avg1joe]

So its accurate, give or take 10-50 feet. Ack.

 

[mdram]

what accuracy do you need?

 

[navychop]

I've had GPS units tell me I was driving along service roads when I was on the main road. It's by design limited in precision for civilian uses. Of course, surveyors and certain others can get much more accurate, perhaps military grade, equipment.

 

[mike123abc]

It just costs a lot more to get a unit that is more accurate. They use ground based transmitters in addition to satellites to help.

GPS.gov: GPS Accuracy

They can get down to centimeters/milometers.