PolishPostal

Just curious if anyone else has notice this. There is always a discrepancy between the ascent total that I get by mapping out routes on Delorme and the data that I download from the actual rides on my Polar 720. I have found a discrepancy in the total as shown in the Polar Precision software and by analyzing the downloaded elevation data from my Polar 720.

After a download to the Polar Precision Performance software some time back I decided to check the data out. So I did a File>Export as Text on one of my rides. I then imported the data into Excel and wrote a formula that check if the preceding elevation was below the current elevation, if so it adds the difference in the 2 elevation to the ascent total. This formula was repeated through the entire data set. Well... by this method (which is what the polar software should be doing) the ascent value was quite a bit larger than the ascent value shown in the Polar software.

What the deal?? Anyone else notice this? I'm contacting Polar to see what they attribute the difference to.

SSP

Polar HRM files are somewhat notorious for inaccuracies. I've seen many such files where the ride distance is shown in Kilometers, even though the watch is set for Miles. This occurs even with the most recent version of their software (and the problem has been reported to Polar, with no fix to date).

That said, I'd probably have more faith in the Polar altitude data than in the DeLorme data. DeLorme tends to overstate elevation gain by 10-40% in most cases. The problem has been reported to DeLorme (back in version 4), but AFAIK it still persists.

One way to assess the accuracy of your Polar unit is to look at "current elevation" when you start your ride, and then note it again when you get done. In the absence of changes in barometric pressure during the ride (e.g., a cold front moving in), you should see about the same elevation when you get home as when you started. If the starting and ending elevations agree, you'll at least know that your unit is consistent...if not 100% accurate.

As for your method of calculating total elevation gain by looking at the data points...that sounds like a valid approach, but it's possible that the Polar software has some built-in triggers and/or filters that do the calculation differently.

Regardless, if you do get a reply from Polar on this issue, please post it.

bob the nailer

I am a polar 720 newbie just started using one, have noticed the same thing, for example last sunday went out for a 53 mile ride, and other than temperature, and time of day, no big weather changes, no cold fronts coming through, and my starting altitude and finishing altitude are 40 feet different. sometimes i wonder about the accuracy of the hrm too, as it showed my max heart rate for the ride at 192, i haven't thought it was more than about 178

BikeWNC

I've noticed that my 720 will consistently under measure ascent by 15% of the actual.

Jim Bonnet

power lines can affect the HR readings..

Jim Bonnet

I'm sort of a climbing nut. I have a 725. I plot my routes using a KLIMB and have ridden several of the routes comparing my data to KLIMB's. The HRM is usually pretty darn close. A ride with 3500-4000 ft of climbing according to KLIMB may show up within 100ft on my monitor. Remember that weather changes will change your altitude. As another poster mentioned, if you start and stop your ride close to the same altitude you should be pretty accurate.

cheers.

johnny99

I don't know anything about how the Polar software works, but I have used Delorme Topo USA. Delorme's cumulative elevation gain feature is terrible. There's a hill near me that has a fairly even grade (all uphill). My Specialized altimeter computer reports about 2000 feet, which is very close to what my USGS topo maps say. Delorme, on the other hand, reports a 3000 foot cumulative elevation gain for the same route. The problem is that inaccuracies in the Delorme database add false ups and downs into the route, which grossly inflate the cumulative elevation gain of almost any hill. Delorme's accuracy improves on flatter routes, but you really don't need an altimeter to tell you the route is flat.

My advice is to trust your altimeter for cumulative elevation gain. It isn't 100% accurate, but it is much better than Delorme. Delorme is fine for telling you where the hills are along your route and how tall they are, but the cumulative elevation feature really sucks. The gradient feature also has marginal value, except over larger distances that can average out the inaccuracies.

Doctor Who

That's nothing. Air pressure changes constantly and the starting elevation will never be the same from the beginning of a ride to the end.

My problem with my 720 is that I can't get my computer to download the exercise files.

F1_Fan

Delorme's altutide feature is complete and total crap for most routes. It tries to extrapolate the data from the contour lines and does a bad job of it. I've got several examples of its errors.

FWIW, I trust my Polar 710i (if the weather doesn't change) much more than the DeLorme software.

Case in point... Hurricane Ridge, WA. Delorme puts the grade at 11% with maximums of 22%. ROFL. I've ridden it several times... my Polar and Vetta 100A get it right... 5.5% average and no maximum over 7%. The Polar also nails the final altitude... 5208 ft. I think the visitor's centre is listed as 5230 ft on the web.

Delorme's elevation feature is crap.

Oh and I should add something. The Polar's cumulative altitude totat (I think... I forget now and I'm full of wine and Guiness) only ticks over when the altitude changes by 5m (?). You can ride along +/- 2m and the Polar won't record those changes towards the cumulative total. I noticed this when comparing to the Vetta 100A which registers every metre. I *think* this is Polar's way of reducing the noise caused by air pressure and temperature variations.