odometer question ( urgent please )

[automotiveforumsun]

How accurate is odometers reading? Can they measure exactly. I mean matching metres, foot and inches travelled by automobile or train?

" OR "

Do we have any means with which we can measure the exact distance upto inches travelled by automobile or train.

[shorod]

Military GPS. The accuracy of the odometer will vary somewhat based on tire pressure and I suppose mechanical calibration of a mechanical odometer.

If you can get by with less accuracy (like tens of feet/meters) you could use commercial GPS receivers.

And, if you were to post what exactly the reason for your question is, others might be able to offer additional alternatives to your measurement problem. The better the information you provide, the more likely it is you'll get a good answer quickly.

-Rod

[curtis73]

The government requires a certain level of accuracy in stock odometers. I don't know what it is, but I've had cars from the 70s that were off by 2-3%. My wife's 97 Tercel was off by almost 5% with stock tires.

So, I guess it depends on your vehicle when it comes to odometer accuracy. My wife's current car is a 99 Mercedes that seems to be within 0.5% accuracy, due in part to the accuracy of the VDO electronic gauges, but if I swapped out the current 205/55-16 tires for another brand, that accuracy might be off by a larger percentage.

Put it this way... odometer/speedometer accuracy these days is more precise than tire manufacturers' outside diameter.

GPS is highly accurate to a few feet, so on the average a long trip using GPS will provide very accurate results.

[jdmccright]

The vehicle measures distance through its vehicle speed sensor (VSS), typically mounted on the tail end of the transmission nearest the output shaft for rwd vehicles. So, this is the reason that a change in tire diameter will throw things off...either with different tires or by changing the air pressure. The key factor is the tire's "rolling diameter" not necessarily its manufactured diameter.

If you REALLY want to check your accuracy you can do this:

Highways have mile markers. While driving, note the mile marker number and your trip odometer (or reset it to zero), then drive, 100 miles is a good length but I'd say at least 50 on the same stretch. Note your elapsed miles on the odo and compare it versus the marked miles. That should give you a reasonable accuracy.

[automotiveforumsun]

for avoiding tire pressure/diameter lets see the following example.

If the tire is solid ( assume it as a rail train ), can we have a consistent and correct readings on odometer for repeated trips between two points? I am still looking accuracy as to the lowest level possible ( inches to 100% accuracy if possible ).

[shorod]

I think you'll have a hard time beating the accuracy of GPS, which is pretty darn good, even at the consumer level, especially over long distances. GPS removes a lot of variables.

Maybe having an understanding of the origin for your question would help get you an answer that you can live with.

-Rod

[automotiveforumsun]

origin of my question is related to some small project that I am planning.

[maxwedge]

Again, and what does this consist of, you have been asked about this 2x now, still no definitive answer! Why the evasiveness, 3 Mods are now involved, but we are in limbo here.

[534BC]

It seems that the increments may be in question more so than the accuracy.
Even at 100% accuracy we could not read a few inches or feet on an odometer.

I'm sure some guru could can figure out how to move decimal over one or two places and increase the sender's output by 10x or 100x to get smaller increments.

Check into some data loggers for trucks, they can read down to a foot or so movement. Hope this helps.

[2.2 Straight six]

Originally Posted by 534BC

I'm sure some guru could can figure out how to move decimal over one or two places and increase the sender's output by 10x or 100x to get smaller increments.

Just change the gearing. Add a little mechanical gearbox and you're set. (These can be bought from places like radio shack and the like.)

[automotiveforumsun]

let me find it by myself. let you know, when i Know it.