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New to GPS, wanna have a accurate ETA for travel and work!

Hello guys, i am new to this forum and i would like to understand which GPS is the best for ETA?
And if anyone could explain the mechanism or logic behind the ETA of each GPS
i will be appreciated much as i am really interested in learning :).
( had search for speed limits? traffic condition? past user behavior? how they related and work!?)

Seems google map always get me the correct ETA before the planning
but i really need a reliable GPS product which
guide me during the drive.

Please help me experts! Thanks a lot!


  • sussamb 764 Points
    I have found all my Garmins to be fairly reliable with their ETA, although it takes a few drives as they seem to 'learn' your driving style. Once learnt ETAs are pretty much spot on, adjusted as necessary for traffic which with the digital traffic receivers in the newer nuvis is also excellent, at least in the UK where I live. Elsewhere it will clearly depend on coverage and in the US I understand traffic coverage isn't so plentiful.
  • Tim 1467 Points
    The method of determining ETA depends both on the manufacturer, as well as the data they have available for the specific roads you are going to be on. So without knowing which GPS model and which roads, the answer will unfortunately vary.

    Generally speaking through, roads will have a classification which is the mapping companies starting point for an estimated speed when no other data is available. Then, as additional information is available it is applied to the ETA to give better estimates. The exact formulas are not something the GPS companies give out.

    For example, you can additionally factor in current traffic conditions coming from live traffic services, traffic magnets, etc. You can also use current traffic conditions from other drivers based on cell phone signals, or even data coming from their GPS.

    Other data sources include historic traffic conditions such as being able to say "along this stretch of road, on Thursdays at 4:30pm traffic is typically traveling at 37mph".

    Still other models will try to apply some personal logic and determine that you typically drive 2mph faster than most of their estimates, so adjust future estimates accordingly.

    Often though, the best ETA will come down to user location. For example where I live TomTom devices provide the best ETA for me, hands down. I can never drive nearly as fast as the Garmin expects me to. On the other hand a couple states away in places I often travel, the Garmin ETAs are much better. (And this is all while ignoring the accuracy of live traffic reporting which doesn't really exist in my local area.)
  • With Garmin if you develop a route with Mapsource or Basecamp the eta will be about right. But the GPS and mapping software have no idea of real world conditions; only speed limits which are in the data base.
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