Cycling Path Profiler

Go straight to profiler.

I like cycling and I often use GoogleEarth to plan my rides. Though GoogleEarth lets me draw a path, it is annoying that I have to go to separate third party tools to work out the total distance and the elevation profile, especially when some of the elevation tools are deliberately throttled back . So in the end what I did is write my own.

I have used SRTM3 files from ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3/. These files contain elevations 90 metres apart for a large sections of the globe. TIP: Try to put a data point about every 90m, especially if the terrain is undulating . Add extra data points around the crest of a hill and the floor of a dip. At the moment I have only downloaded the srtm files for South East Queensland, where I do most of my riding. If you contact me at l.rathbone at uq dot edu dot au and ask nicely I might upload the files for your area :).

You need to save your path as a KML file. Just right click on the name of the path and chose "Save Place As". Make sure you save as KML.

It's not perfect but it works for me. You can try it here. You should get an image the looks like:

Profile image

That is supposed to be a 3D effect. I thought it looked cute.

What's a Climb?

I have used red to highlight the harder climbs. It is more difficult than you might think to define a climb. Firstly the elevation points are only accurate to within 45m of the path. (The grid points are 90m apart and you could be right in the middle.) So sometimes where I know a climb is continuous the data will show a decline (the nearest elevation might be over the edge of that cliff!) So I have tried to make allowance for this with an error margin between readings. I have played with this a lot and it seems to be reasonable around 1m. So if from one reading to the next there is a drop of upto 1m it is ignored and it is still considered a climb.

Next, what rise in elevation constitutes a climb? 1100m l'Alpe d'Huez? I eventually decided upon 30m. Your average garden variety cyclist is going to know they are climbing if it is around this figure. This brought in a problem when there really was a decline. To counter this I set a "flat section" threshold of 100m (more than one grid section if in a straight line) and if the path continued to decline or remain flat for more than this length the climb is considered over. Of course on steep hills the roads tend to loop back rather than be straight so the threshold is just a guess. I played with a number of rides I am familiar with and it seemed to mark the tougher climbs.

On inclines of 6% and above I have put a little label, just to let you know about the joy ahead. The percentages are probably less than you might expect because I take the measurement from the very start of the rise - which might be gradual before it kicks up. (In the Mt Glorious example above, the 6% climb is Split Yard Ck. It has a incline of about 15% for a short period)

The image is sized so that you can print it out and tape it to the top tube of your bike. It will give you a good idea of what to expect. Then you can really enjoy hitting those hills! Unfortunately, it won't make you go faster.

I hope you find it useful.

Mention l'Alpe d'Huez and I had to try it out. Interestingly the program thought there were a couple of flat spots? I haven't been there - maybe just some anomalies in my path.

L'Alpe D'huez Profile image

This file last modified Monday March 23, 2009

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