Discrepancy between odometer and sat nav

[Alison01326]

If it's a vertical hill and you travel forwards, you will find it's a bit like banging your head against a brick wall

[widdowson2008]

Well there is where you are going wrong ..........

I said a mile TRAVELLED uphill, so now redo your diagram with the slope of the "hill" as the 1 not the horizontal and vertical distances.

Perhaps I should have said "it sees you travel 0.8(ish) of a mile whereas the side view and the odometer shows you have actually travelled 1 mile".

Where did you get the idea I had driven 1.414miles up the hill? I didn't say that.

I'm not disagreeing with Pythagorus

Total misunderstanding on my part scanner - I do apologise.

[HangTen]

The guy responsible:



Pythagoras of Samos (monument in Pythagorio harbour, Samos island, Greece)

[francophile1947]

The guy responsible:



Pythagoras of Samos (monument in Pythagorio harbour, Samos island, Greece)

Ah Somebody has broken his triangle

[mikexgough]

well it's all as clear as mud to me......

[dave_aber]

[pedantic mode on]

You are almost right there - except that GPS does calculate your height - so does measure the 'slant range' not just the horizontal range seen in plan view.

However, although GPS is very accurate, it is pretty crap at determining height - so quite often gets the height bit of the calculation wrong. This is where the discrepancies come in.

[pedantic mode off]

And here is why

[bigdaddycain]

How intriguing is this? (no really, i was determined to fully understand all this rather than just click off the thread with unanswered questions) I just demonstrated the principle to my daughter (she was wondering what i was doing with my arms) I'm lay on the floor here with my laptop in front of me. Whilst still lying down i raised my left arm (elbow resting on floor) straight up, then lay my right hand on the floor with my fingers touching my left elbow, now raise your right arm to a 45 degree angle (simulating a 1 in 1 gradient) You'll notice that your fingers are quite a bit short of touching your other fingers, thus more distance needs to be travelled to make the fingers meet. Yep, follows the maths, which of course MUST be correct, maths is always correct, but not always implemented correctly.

[mister munkey]

I'm scratching my head too.

1 mile in 40 is about 2.5% which is around how much my speedo is out by. Could the odometer to satnav miles be explained by the "natural" over-reading of the speedo?