I use to run with a Garmin Edge 305 which uses a barometric altimeter for its elevation data. It's accuracy is certainly not scientific grade but gets the job done. I usually ran it recording data every 3 seconds versus every second. For one it seemed to 'smooth' the data better and give a more accurate tally when it came to accumulated elevation gain versus the 1 second recording option which seemed to inflate the data. But I used the thing for probably 25K miles or so and felt pretty confident with the elevation data I logged. Long rides over the same course would be within a few hundred feet of one another.

I've noticed that roadside signs are generally misleading. I think a lot of people take these as fact. I'll see a sign for a hill with a 19% grade on it and after riding it a few times and taking readings stopped in strategic locations, that the only place even close to the 19% is like a 10 foot section on the inside of a switchback, and the whole hill averaging half the stated grade.

I never pay much attention to the grade on small hills. It would be hard to avoid double digit grades on a ride of any length here in Vermont. I like to think more of an average grade over the course of the climb. It's certainly not as glamorous. Example: Bolton Valley Resort's access road. It's 4.25 miles to the resort after you turn off route 2. It rises about 1800' making the average grade roughly 8%. Doesn't sound like much when you say 8% but it's a tough four miles for sure.

Enough of my rambling.

~kn