Vertical Challenge - More Hints & Tips

Many Harriers have been out recceing their hills over the week and from that we have learned a few more things or a few questions have been raised. Here are some more hints and tips arising:

Remember that GPS cannot measure height or elevation with any useful accuracy. The clue is in the name Global Positioning System - the GPS measures horizontal position on the earth's surface only (if you have one of the more expensive Fenix running watches or Edge cycling computers, they have a barometric altimeter built in which provides accurate change of elevation data to your Garmin session. Most of us don't have that though). So if your watch displays elevation on its face and it is not equipped with a barometric altimeter, the elevation is not accurate. You have to upload to Garmin Connect or Stava to get a more accurate indication of elevation gain.

To determine elevation for your session, Garmin and Strava look up your position on their own databases of terrain height when you upload your session. Although they are mainly using publicly available height databases, they have also developed their own height databases based on analysing the millions of users' sessions which have been created with barometric altimeter equipped watches. These data cover popular running and cycle areas only. For the remote areas they will use the public height databases which are quite low resolution (e.g. one point every 50m) and tend to smooth out the terrain. Not a problem if you are covering a large distance on your session but can result in errors when the hill is only 100m long. As Strava and Garmin have their own elevation databases, they usually don't give the same elevation gain result. Submit the result and link from which ever app gives the highest elevation reading (Garmin Connect or Strava).

Garmin and Strava have also developed their own algorithms to try to correct the elevation for GPS positioning error. You will notice that even if you run up and down the same bit of road, the GPS track is a squiggly line which does not follow the same path each time. Garmin and Strava analyse this and decide that you probably were running up the same bit of road and use exactly the same altitude data for each ascent and descent to give the same smooth hill on each ascent. Of course, if you really are running a squiggly course up the road, to pick a steeper bit of terrain, this may not be captured! Furthermore, Strava (don't know about Garmin) have developed algorithms that compare your position to street and footpath maps. If it looks like you are very close to a road or path that is used by other Stava users, they look up the elevation data for that road or path and use that. So, the other day one member walked up a very steep grassy slope in EK which was very close to a footpath that went around the hill rather than up it. Strava recorded only a couple of metres elevation gain whereas it should probably have been about 10m. It is likely that Strava assumed he was on the path, which only climbed a couple of metres, rather than on the grassy bank beside the path. Therefore, for the vertical challenge, stick to hills that are on roads, pavements and well defined paths otherwise you may suffer from Strava being too smart for its own good.

Another Harrier tested the same steep hill on a road in EK 3 times (Glenburn). The first time she ran up 150m, then 200m and finally 250m. The height gain for all 3 ascents was 15m on Garmin Connect and in this instance Garmin Connect gave a higher height gain than Strava. It therefore makes sense to only run 150m up this hill and to use the result from Garmin Connect. Do a recce and walk or jog various distances up the same hill, download your data to Garmin/Strava and check how little distance you can get away with for the same elevation gain. The shorter the hill, the more reps you might manage.

The elevation gain you are to submit to Scottish Athletics is the one on the main screen of your Garmin (67m in this esample) or Strava (54m in this example) session as shown below.

The Scottish Athletics instructions for uploading your results (the same as for the previous challenges) are in this pdf document. Make sure that your session is "public" before copying the link otherwise Scottish Athletics won't be able to view it.

The specific rules for the event are here.

Finally, set up your watch in the same way as we did for the 30 minute challenge as shown in this post/video. This avoids any button press errors when suffering from altitude sickness at the end of the session! Note that you could also set it up using the interval function on the watch as e.g. 2 x 7.5 minute reps with 2 x 7.5 minute recoveries no warm-up and no cool down. This will run for 30 minutes and stop automatically. All you have to do is remember to save the session!

Thanks to everyone for all the enthusiasm you have shown for this and the other virtual challenges we have done. Have a good one!
Alan