Accurate pedometer

A GPS-pedometer wouldn't be much use for walking in the woods (under dense trees), walking indoors (e.g. a shopping mall), or walking on a moving platform (like a cruise ship).

Kidding about getting a free GPS when you test drive a car. Just how cheap are these things? I did a little poking around and most of them seem to be $200 and up. -- Mike

Local Cadillac dealer was giving away a Garmin GPS 38 for doing a test drive. Appeared to be a corporate offer as the GPS was delivered in the mail a few weeks later. I didn't need either a new car or another GPS, but a good friend of mine went and did the test drive just to get the GPS. You can get a GPS good enough for pedometer purposes for under $100.

Doug

GPS Doesn't work under trees? I dod not know that.

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As underlined.

Depends a bit on the quality of the GPS. I know mine doesn't. (HandyGPS Pro on a Visor)

Meindert

Pro

The GPS my friend uses for work works under trees. The only trouble is it's got an 18 inch diameter antenna and is held over his head attached to a pole on a backpack so it's a little heavy. Not exactly a very convenient pedometer but very accurate if you are a cartographer.

Peter

By the way, that should be attributed to me.

To continue this OT thread, there are trees and there are TREES. (I live in the Northwest U.S. where the 100+ foot pines, firs, larch, etc. do a very effective job of signal attenuation at 1.6 GHz).

-- Joe (Remove "NOSPAM" to reply via Email)

You might be surprised, actually. A good GPS will work in most buildings, and even do well in fairly dense tree cover. In the woods, a conventional pedometer wouldn't have much practical use either.

Anyway, I like some of the other ideas presented here better.

Not sure how you quantify a "good" one. My Garmin GPS-196 isn't a "bad" one but doesn't report any satellite signal strength in my aircraft hangar or basement. Nothing indoors at work either. Neither do my older Lowrance or my newer Magellan "hiker's GPS" units.

One particular problem with pine and fir trees is that their needles can be about a half-wavelength long at the frequency of interest. The GPS signal is attenuated very effectively.

The practical use of a conventional (or otherwise) pedometer in the woods would depend on the woods. Again, here in the northwest, we have "woods" (forests) with trails that go on for miles.

I have a Garmin StreetPilot. I'm sure I could find places where it doesn't work (the bottom of Oak Creek Canyon, AZ is one) but I've used it in fairly dense woods, and inside many buildings (including shopping malls), so I still think the original statement was too broad a generalization.

Even if you would get some usable signal levels inside a building through reflections from nearby buildings or sneaking through some air conditioning ducts, the path distance from the satellite to the receiver would be much longer than when the receiver is outside.

Since the receiver location is calculated from the trigonometric distances from each satellite (at known positions), most likely the calculated location would be 100 m below the ground and if it happens to be near ground level, quite a large number of meters away from the true position. If some satellites are received (nearly) direct and some trough long reflective paths, the position will be biased in some direction.

Worst of all, when moving in such an environment, the path lengths will constantly vary and hence, the calculated position will jump wildly. Trying to calculate a speed from such position reports would be quite meaningless, since the speed would vary much faster than a pedestrian can walk :-).

Of course some receivers will employ various kinds of filters (Kalman etc.) to reduce the position oscillation, but on the other hand, they will respond slowly when the users gets out of a building with a lot of bad readings in the filter.

Paul

You should broaden your world a bit. I live in a country were 99% of the building floors are reinforced concrete. So my 'actual experience' is that a GPS never works in a building. It is all a matter of perspective....

Meindert