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Car Forum / Honda Cars / September 2004Accord GPS "time to destination" error
A good friend has a new Accord with the GPS navigation system. For whatever reason, while it perfectly pinpoints his location, the estimated time to destination is off a good 30%. It's as if the system is reading the car's MPH with a 30% error on the slow side. However, the car's speedometer is accurate, as is the GPS position location. We've confirmed that other similar models (of the same year) do NOT have this problem. Basically, the dealer is clueless as to what to fix, as they've never seen the problem and don't know what to do. So, they refuse to do anything. The car's GPS system has this problem consistently. It's not intermittent. You can put in a destination 60 miles away (for example), proceed to drive 60 miles an hour, and it'll tell you that you're 1:18 away (instead of 1 hour). Do any of you experts out there have a clue? TIA. Neall I don't have the built-in navigation system, but I use a GPS on the dash with a laptop computer. My system determines car speed and location strictly from the satellites, it has no connection with the car's components. I would expect the Accord to do the same, so I would look to upgrade the DVD software for a possible fix. On the other hand, if this error is so predictable, you have one of the easiest issues to overcome... Al A good friend has a new Accord with the GPS navigation system. For whatever reason, while it perfectly pinpoints his location, the estimated time to destination is off a good 30%. It's as if the system is reading the car's MPH with a 30% error on the slow side. However, the car's speedometer is accurate, as is the GPS position location. We've confirmed that other similar models (of the same year) do NOT have this problem. Basically, the dealer is clueless as to what to fix, as they've never seen the problem and don't know what to do. So, they refuse to do anything. The car's GPS system has this problem consistently. It's not intermittent. You can put in a destination 60 miles away (for example), proceed to drive 60 miles an hour, and it'll tell you that you're 1:18 away (instead of 1 hour). Do any of you experts out there have a clue? TIA. Neall > I don't have the built-in navigation system, but I use a GPS on the dash with a laptop > computer. My system determines car speed and location strictly from the satellites, > it has no connection with the car's components. I would expect the Accord to do the > same, so I would look to upgrade the DVD software for a possible fix. On the > other hand, if this error is so predictable, you have one of the easiest issues > to overcome... Al The built-in navigation systems use the signal from the vehicle speed sensor in addition to GPS. Most of them also use a gyroscope. This provides for more robust navigation in areas where satellite view may be spotty, like in tunnels, parking garages, and when you are surrounded by tall buildings. Newsgroups are ASCII only forums, so please turn off your HTML or "Rich Text" (or whatever you are using) when posting to newsgroups. Hmmm... don't buy that, the only way the navigation system knows where you are, and how far you are from where you are going is with satellites. Perhaps the Accord navi uses the vehicle speed connection, but that is not more accurate than the speed determined from satellites, nor does it help when satellites are not available because of obstructions... Al BTW, thanks for reminding me about using ASCII for posts > The built-in navigation systems use the signal from the vehicle speed > sensor in addition to GPS. Most of them also use a gyroscope. This > provides for more robust navigation in areas where satellite view may be > spotty, like in tunnels, parking garages, and when you are surrounded by > tall buildings. "aljudy" <nowhere@yahoo.com> wrote in news:_T3Zc.10244$QJ3.3219 @newssvr21.news.prodigy.com: > Hmmm... don't buy that, the only way the navigation system knows where you > are, and how far you are from where you are going is with satellites. [quoted text clipped - 9 lines] >> spotty, like in tunnels, parking garages, and when you are surrounded by >> tall buildings. Honda's manual does describe the navi system in the Odyssey as also utilizing some sort of inertial guidence system, a small gyro.  Signature"All my friends can't be wrong!" Remember, stupidity runs in herds. "Dr.Maggot" <Maggot@nospam.invalid> wrote in news:Xns9556991572EBEDrMaggot@ 130.81.64.196: > "aljudy" <nowhere@yahoo.com> wrote in news:_T3Zc.10244$QJ3.3219 > @newssvr21.news.prodigy.com: [quoted text clipped - 17 lines] > Honda's manual does describe the navi system in the Odyssey as also > utilizing some sort of inertial guidence system, a small gyro. And as an additional point, when I am descending down a multi story, enclosed, concrete parking lot the system know exactly which way I am going and accurately tracks my travel. I don't think satellite reception is all that good. My Garmin handheld, for example, does not work in that same environment. Signature"All my friends can't be wrong!" Remember, stupidity runs in herds. > Hmmm... don't buy that, the only way the navigation system knows where you > are, and how far you are from where you are going is with satellites. > Perhaps the Accord navi uses the vehicle speed connection, but that is not > more accurate than the speed determined from satellites, nor does it help > when satellites are not available because of obstructions... Al Navigation systems can be made entirely without GPS (or other satellite or terrestrial based navigation network). Etak (now TeleAtlas, http://www.teleatlas.com) did this back in the mid 80's. One version relied only on speed sensors at the wheels, distance traveled was calculated based on average of left and right sensor, changes in direction were calculated based on the difference between left and right. The path traveled was matched with an electronic map; the system would assume you were traveling on actual roads and find the best match of known roads the the measured travel path. Upon initial installation of the system, a calibration run had to be made to allow the system to know the characteristics of the wheel sensors and suspension geometry. An initial absolute location would have to be entered as well. As tires wore down etc. the system would recalibrate itself. The system worked well, except for in larger cities with streets in a regular grid pattern. Here, the system would occasionally get confused as to what street you were turning onto. E.g. if you were driving down 2nd ave. for miles, and then made a right turn, the system would not be accurate enough to know if you were turing on 56th street or 57th street. The system had menu selections for "Skip one street ahead" and "skip one street back" to overcome this. If you got wheel spin (e.g. while driving in snow and ice) the system would get confused as to what direction you were traveling in. On early systems, the electronic maps were stored on cassette tapes. Later gyroscopes were added, and the maps were put on CDs. Gyroscopes were added later (I have one of the early gyroscopes sitting on my shelf) and experiments were done with using a compass also (turned out the compass confused the system more than it helped it due to local variations in the magnetic field etc.). Navigation without the help of GPS (or similar systems) is called dead reckoning, and most of the navigation systems that are permanently installed in cars have some form of dead reckoning in addition to GPS. If you know where you are (based on GPS data) and then loose the GPS signal, dead reckoning will give a very accurate estimate of where you go until you receive a GPS sugnal again. Thanks Randolph for sharing your knowledge here... Al > Navigation systems can be made entirely without GPS (or other satellite > or terrestrial based navigation network). Etak (now TeleAtlas, [quoted text clipped - 5 lines] > would assume you were traveling on actual roads and find the best match > of known roads the the measured travel path. > Thanks Randolph for sharing your knowledge here... Al You are more than welcome. A few years back I had the pleasure of working with one of the founders of Etak. He was happy to discuss the details of the navigation system, and also showed me one of the very early ones that he had installed in his car. >Do any of you experts out there have a clue? TIA. Neall Maybe it discounts speed for traffic lights and such. I wonder if (please excuse me) there's anything about this in the owner's manual? J. > A good friend has a new Accord with the GPS navigation system. For > whatever reason, while it perfectly pinpoints his location, the estimated > time to destination is off a good 30%. It's as if the system is reading > the car's MPH with a 30% error on the slow side. I don't have a clue, but I will say that my Accord's estimated times are right on, and even corrects itself while driving if going slower or faster than normal. However, my dad's Toyota Prius seems to be off in this regard. Turns out that, on his car, it simply uses three different default speeds for all highway, surface street, etc. routes (or something like that), and you can go in somewhere and adjust those speeds to your liking and to match present-day driving realities. You might have your friend dig into the NAV manual to see if that adjustment is possible on Hondas as well. Rob |
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