On 3/9/2019 4:46 PM, Sir Ridesalot wrote:
Talking about GPS units on another thread reminded me of something else I wondered if they do. Does a bicycle GPS unit show you the steepness of roads? There's an area that I frequently ride where on road has short but very steep hills, another road a mile or so east of it has much more gradual hills whilst a third road to the west of the first one is a major highway that can be ridden with a bicycle. What I'm wondering is this: if someone unfamiliar with the area got there and used a GPS unit to show those three roads, would the GPS unit show them the different gradients of the roads? Or is that another function that they'd need to download or otherwise install?

Cheers

As others have noted, many (all?) Garmin units can display gradient (as
in "6% grade". As noted in another thread, GPS units are notoriously
not very accurate in their altitude calculation, so the more expensive
units have a barometric "backup". If you are using a pre-loaded course
(e.g. a .TCX file) on your GPS, (?some? ?all? my!) Garmins can display
the profile of the upcoming few miles.

My own experience over 7 years with Garmin units (that have barometric
"backup" to the altimeter calculation) is that the reported gradient is
/fairly/ consistently reported (on many rides over the same hills),
though the peak steepness will vary by a percent or so. Maybe that's
'cause I wasn't looking when the highest number was on the screen, or
because the unit updated at different points on the road on different
rides of the hill.

Finally, if you use ridewithgps.com, and I assume any similar
sites/software, note that gradient reporting there usually misses peak
values, as the software tends to average over larger segments of the
course. For example, on one local hill I ride a lot, the peak gradient
appears to be about 12% for maybe 50-100 feet, as measured with both GPS
and inclinometer. Ridewithgps.com reports a peak of 7.2%, which is
probably true if you average over longer segments.

Mark J.