My recent experience using a barometer in a smartphone is that it gives a more accurate ascent/descent figure.
I base this opinion on a check of spot heights published on Ordnance Survey Mapping.
I picked out the low and high spot heights along the route and then calculated all the height differences to produce overall figures
Bob, I am afraid that is one of those questions like how long is the coast of Britain. This is presumably why Plotaroute offers the adjustment option, which lets you draw some rough comparisons between different datasets.
It would be good if there was a standard way of measuring accumulated climb/descent. To my knowledge there isn't any, but I'm not too familiar with this subject.
Your reply much appreciated. As it happens I have been QC'ing the various elevation dataset available for the UK. All are good though I have found that the SRTM 1arc has some data QC issues with spurious small altitude changes that can overestimate on altitude gain calculation by up to 15%.
We use the SRTM3 data. It's worth bearing in mind that the algorithms used probably have a bigger effect on the ascent calculations than the granularity of the raw data, in particularly the sampling frequency, which is often very variable. For this reason I would advise against trying to draw comparisons between ascent figures from different sources. If you haven't looked at it already, have a look at some routes in our route profile tool and adjust the elevation interval - this will give you an idea how much the sampling frequency affects the ascent figures.
In our club we have much discussion about which route plotting website gives the most accurate elevation profiles and calculations of total ascent.
I have thus been investigating the widely available elevation datasets that I assume are being used and find that they can give some quite different results.
Can you tell which elevation database Plotaroute is using, for exmple SRTM 1arc sec or SRTM 3 arc sec?