Navigation Time/Distance Inaccuracies

My 2006 RTL came with navigation which I thought was cute but somewhat useless in Montana.

After two years of owning this thing, I decided to "program" the drive from a motel in Billings, MT to my home address in Missoula, MT, a distance of about 375 miles. The navi computed the distance to be 280 miles and about 13 hours of drive time! As we got closer to home the distance inaccuracy narrowed, then became more than the actual mileage distance, then pretty well got to 00:00 as I drove in the driveway.

We drove to Portland, Oregon a few weeks later and the distance was almost correct to the address we were driving to but, again, the drive time was estimated at an average of about 30 mph.

The route suggestions were right on the mark. What's going on here? Maybe this is why Honda didn't include a driving computer that postulates mpg, etc.

I was once told that most GPS units sold to the average public do not account for altitude gains / losses which will result in milage descrepencies.

I do not have Nav on my RL, but I assume yours works like other brands.
In a setup screen somewhere, you have a chance to enter your travel speed for several types of road, usually freeway, main artery, residential and sometimes rural. The Nav system then calculates your travel time based on the number of miles traveled on each type of road and the speed you entered for that road.
After several months of fine tuning the speeds based on the way I drive, My travel times are within a few minutes of prediction for most trips in my Lexus w/Nav.
One of the other members with Nav can probably help you locate that screen

The accuracy of the unit that you lack is a product of what I believe is called the "mapping engine" or similar. The mapping engine is supposed to be the brain that calculates the time and distance for the trip based on the route information programmed into the unit. The accuracy of this calculation is a result of both the mapping engine and the maps programmed into the unit. Who knows what Honda uses.

The best mapping engines on the market are on the Garmin units. Garmin uses it's own mapping engine and it's own route data. Together they are pretty darn accurate and can land me to arrival within about 5 minutes of the original prediction on a 2 hour trip and within about half hour on an all day trip. The Garmin will dynamically adjust its expected arrival time evenly during the trip.

With my Garmin units I don't program anything into it other than the destination it seems to know everything else by itself.

I want to asterisk this whole post by admitting that I am nearly totally uninformed about these units except that I am pretty sure they work as described and I am also positive the Garmin units are the most accurate.

I read somewhere the undigitized areas were calculated at 25 MPH. If I am not mistaken the engine is Map Quest.

The 2006 Honda Navigation seems fairly sophisticated in its setup and operation. One can choose whether to use or avoid freeways for instance or choose the "direct" route. I haven't found a choice selection for my intended mph driving speed yet. All of the routes I mentioned above were primarily Interstate Highways the whole distance until entering Portland, for instance. The original DVD that controls the graphics and routes (I think that's what it does) is sort of out of date. The main artery to our home in Missoula isn't on the map although it's been there for almost 20 years!!

But the inaccurate estimation of distance and time disturbs me. I am certain Honda knew about this and for that reason didn't incorporate a driving computer that would give you speed, mpg and fuel left, etc. Without basic accuracy in time/distance the unit could not possibly compute mpg, speed, etc.

Thanx.

The 2006 - 2008 Ridgeline nav system does not have any trip computer or MPG calculations.

The distance is actual road mileage of the selected route as long as all roads are within the verified base map.

When the route includes roads that are not verified the mileage is estimated and the time to travel is calculated at an assumed 25MPH average (as stated above).

If you think you've found an error in the base map you can report it at: http://update.navteq.com

This is the screen I was describing in my previous post. Lexus, and probably all Toyota product Nav systems use this to fine tune the estimated travel time.

OK, here we are two weeks later from my original post.

Saturday I drove to a specifice address in Billings, MT again about 350 miles from my address in Missoula, MT. (I have not been able to find anywhere to adjust my driving speed for the computer).

So, the computation to Billings was very accurate in time and distance. When we finally got within range of mileage billboards (about 200 miles out) the distance on the navi was within 2 miles all the way to Billings. The two miles represented the in-town driving from the city limits. So far so good.

Two hours later I typed in my home address from the Billings destination and began the trek home. BUT the distance to home was 80 miles short and computed for 13 hours!!! What the heck is going on?? I used the exact same route going and coming home. Except for in town routes, all of which were on the graphics (except the last 1/2 mile from my house) the route was Interstate 90. The computer did "catch up", i.e. slowly compensated for its original time/distance error.

Should I invest in an update CD? That doesn't seem like a logical solution; it seems like internal firmware of the computer. Or should I forget this thing as a useful OEM tool?

Tom

#1 Make sure you have selected Direct Route as the routing method. You may have selected to Minimize Freeways which would result in the error.

#2 Your unit may be defective. From Billings, MT to Mossoula, MT shows 342 miles and 4:45 using version 4.64 map data.

No, I don't think a DVD update will help.

The adjustment of speed is not an option as was mentioned earlier.

I suspect you have the incorrect routing method selected is the only problem.

I suspect you have the incorrect routing method selected is the only problem.

I think so too. Your truck should have come with a Nav manual that you can read through or you can get on to the Owners Link and look at it on there too. I like to choose esay route for my routing info. Also if you are still with in Warrenty take it to the Dealer and tell them what going on.

#1 Make sure you have selected Direct Route as the routing method. You may have selected to Minimize Freeways which would result in the error.
#2 Your unit may be defective. From Billings, MT to Mossoula, MT shows 342 miles and 4:45 using version 4.64 map data.

No, I don't think a DVD update will help.

The adjustment of speed is not an option as was mentioned earlier.

I suspect you have the incorrect routing method selected is the only problem.

Thanks for your suggestions. Since the most direct route is on Interstate 99% of the way (the 1% represents the distance from city addresses to the Interestate) I believe it's set on maximize freeways. The important point is that I used the same routing method both ways.

Perhaps there is a defect. I now have 42,000 miles on the RL so I'm out of factory warranty; perhaps my aftermarket warranty will cover it.

From Billings, MT to Mossoula, MT shows 342 miles and 4:45 using version 4.64 map data.

For comparison, using Garmin Map Source shows 343 miles and 5:14 for an average of 65.54 mph.