# Finding Elevation Change, any method

So, I think it'd be cool - for goal setting for example - if I could keep track of my elevation change.

The problem is, the local cyclocomputers I looked at seem to use barometric pressure to determine the change. This is fine, unless some weather is moving in, which happens not infrequently in the Midwestern United States.

Or do some of them try to use an inclinometer, your speed, and some math you learn in Calculus II to keep track of your change? That would seem more accurate!

I could try to use a GPS meter, but those things are expensive - and based on back when I had service to my smart phone, not guaranteed to match my car's odometer for distance even - I've read from some other riders that the distance varies at least slightly from local measurement on a bike as well.

Alternatively, let's say that I ride along a known route. Is there any good way of plotting that route for elevation change?

Thanks!

• – amcnabb Jul 9 '13 at 16:20
• For known route, MapMyRide web app will show elevation as a graph. – Ken Hiatt Jul 9 '13 at 19:11
• Just to update this: all mobile apps now do this reasonably well. See Endomondo, MapMyRide, Strava, etc. – andy256 May 12 '15 at 11:30

The simplest on-the-road solution is to get a detailed paper (walker's?) map with contour lines. In the UK, Ordnance Survey provide these, for the USA you could try Omnimap.

Alternatively, there are plenty of online tools, like freemaptools.com which use Google Maps. You click on a point and it gives you the elevation.

Barometric pressure is not the only feasible method to track altitude, but is by far the more practical in terms of power requirements (I have a watch that lasts 2 years on a battery with altitude), size and cost.

GPS Altitude is wildly inaccurate due to the geometry of the satellites. Unfortunately to cope with very small signal errors you need a satellite below you, but the signal cannot get though the earth, so GPS altitude will never be as accurate as its position reports. However, a GPS track, overlaid on a topo map with contours gives a reasonable approximation. Be warned though that in mountainous country a few meters of error and result in significant error in reported altitude, especially in forested terrain. It comes down to the accuracy of the maps, and the GPS track - on flat / rolling ground with accurate maps, it works well.

Incline meters and Accelerometers do not work on there own. However, with a connection to the wheel for speed sensing, they can use acceleration and speed and work out incline, therefore height gain. I am not aware anyone does this...

Inertial navigation systems (based on gyros and accelerometers) can achieve what you require - after all, that is all the space shuttle had to go on, but comes at a cost and weight that blows most peoples budgets.

So this leaves us with barometric pressure and its one limitation - it is affected by weather. I have successfully use it (in conjunction with a map) while climbing mountains in complete white out (10ft visibility) to accurately navigate over a 10 hour day. The trick is to recalibrate if a weather system is likely to be affecting it, and be aware that weather systems do affect it and in what way. When you get to a point of known altitude, check what the meter is says, and either recalibrate or note the error. If you do this once every hour or two, the error will be small, unless there's a severe weather system crossing over.

There are systems that combine GPS with barometric pressure and overlay the track onto topo maps. These probably give the best solution of all.

• Do you know why sir, no one does this? I was thinking about using a raspberry pi to set up my own system, mabye with a double life cellphone battery. – user1833028 Jul 9 '13 at 21:42
• @user1833028 Plenty of sport-oriented GPS units include barometric pressure sensors. One manual states, "By default, the device is set to auto-calibrate the altimeter using GPS elevation. Auto-calibration uses the average GPS elevation as a basis for the barometric elevation". I assume this gives pretty good accuracy. – amcnabb Jul 9 '13 at 22:04
• In the absence of calibration, any starting point is better than none - Under ideal conditions, GPS Altitude is good to about a hundred feet, some due to the ellipsoid, some due to transient errors. Outside ideal conditions (under trees, in valleys, urban canyons etc), the GPS altitude is very unreliable. The Barometric reading will normally give accurate deltas - reliably 5 meter resolution and over a short (4hour or so) time frame 10 meter, and works all the time. I have personally witnessed a GPS altitude variation of 150 meters over about 1 minute(while standing still). – mattnz Jul 9 '13 at 22:52
• Barometric pressure, can be amazingly accurate. On my GPS, it will give a 1 meter difference between being on the ground, and being held near my belly. It will go up another meter if I hold it above my head. That's pretty accurate as far as I'm concerned. It may give different reading on different days due to weather, but it's hard to beat barometric pressure for measuring changes in altitude over a relatively short period. Also, I haven't noticed the start and end of my rides being at different altitudes, so the change in pressure over the length of a ride doesn't seem to be that big. – Kibbee Jul 9 '13 at 23:15
• The Garmin Edge 500 has a GPS and barometric sensor. I've set a fixed altitude point at the end of my drive so the sensor always starts at the right altitude. – James Bradbury Jul 10 '13 at 8:44

My solution to the problem is to grab my phone, record my biking trajectory with sports tracker (no data plan is needed) and get an estimation of the elevation (total number of meters uphill, and total number of meters downhill) with the help of GPS. For this you'll have to have:

• a smart phone with a gps (android, apple ios, nokia, or microsoft phone)
• install the app on your phone (with e.g., wifi)
• climb on the bike, start gps, start the app, start recording your workout
• jump off the bike, stop the workout, save and sync the workout. In case you have a data plan, it will be uploaded on the server. In case you are not - you'll need to sync the workout when you'll have the wifi connection
• open the workout in the web site of the sports tracker, check the accumulated downhill and uphill values and the elevation graph

I am afraid that you cannot see the elevation in the phone itself with the help of sports-tracker. It is computed after you upload your trajectory to their server.

Estimating the elevation is a tricky problem and may be quite inaccurate (in contrast to lat/lon estimation of the GPS coordinates). In case you need something a lot more precise, you may export your path in sports tracker as gmx track, import that into google maps and get a bit better estimate.

If you ever plan to move to Europe/Germany then you could use open route service developed by some Academic institution (but which one?), save your trajectory as gmx file, and get the elevation visualized with the help of e.g. GPS Visualizer. See screenshorts below.

Hope you find the post useful.

• I Completely agree with this kind of solution, I would like to suggest other applications that can be useful in the same Manner: Wikiloc: App + website oriented to route sharing, also free. Endomondo: App + website, free and "premium" options. Oriented to workout tracking, offers several statistics. Finally: GPS Logger: App Only, just records gps track files (KML, GPX) that can be later loaded into Google Maps, Endomondo, Google Earth, or many other. Has the advantage that it shows the altitude instantly while recording so you can know it without further analisys. – Jahaziel Jul 9 '13 at 20:05
• @Jahaziel: GPS Altitude is wildly inaccurate for this purpose due to the limitations of having all the satellites above you. – mattnz Jul 9 '13 at 21:15
• @mattnz: Frankly speaking, I do not think that the estimation of the altitute from the satelites directly can yield any good estimate. If the satelites are above you, one may expect a slightly better estimate (in this case the x/y coordinates would be severely messed up). Even in this case I would not bet on the estimate. Estimating the altitute using the estimated lat/long and maps is a different subject though. High definition maps for lat/long with altitute (e.g., google) exists yielding a lot better estimates – arthur Jul 10 '13 at 14:16
• As I commented in my answer - there are limitations of using maps - especially in mountainous terrain (think where 10 meters sideways could be 50meters vertical). As long as you account for such limitations its a reasonable method. – mattnz Jul 11 '13 at 1:23

Since you state that "any method" would do, and taking into account that there are several arguments against GPS, I would suggest a couple of non technology solutions to the problem you have with barometric altitude.

You want to use altitude information for goal setting, which I assume requires more precision than simple route tracking, for which GPS imprecision of 10 meter over a climb of 500 meters is barely an issue.

Method 1: An assistant, a second barometric altimeter and means of communicating with the assistant. Easy as cake: you calibrate both altimeters (cycle computer with altimeter) at the base of your climb, and leave one with your assistant, whom is supposed to remain at the same spot (or at least at the same altitude) and take the other on the bike. When you finish your climb communicate with your assistant, asking him or her to annotate both altitude readings and possibly timing data and any other factors.

Hopefully, even if the weather changes during your climb, you should't be so far away that the two altimeters are in different weather zones... Or maybe you and your assistant can also share actual weather observations and roughly combine that with weather information to discard, let's say a low pressure weave sweeping over only one of the altimeters...

Method 2: If your ride is a closed loop, or you descend using the same route that you climb and if it is possible to descend real quick, you can annotate the altitude at the low point when you begin, a the high point when you finish climbing, then descend as fast as you safely (and enjoyably) can, and note the low point altitude again. With this third lecture you can tell if there really was a barometric pressure shift during your climb.

Of course this assumes you descend quickly enough as to disregard weather changes, and that your goal was just to climb a relatively short distance. (i.e. not day after day travelling).

Method 3: Known Routes. If you are travelling known routes the best approach would be to get maps that contain the appropriate elevation information. In this cases, you can use GPS location data just to find your spot in the map, but then relying on the altitude information on the map. Use common sense to overcome imprecision from your gps device (the least expensive are the less precise), for example, use cue points located in big, roughly level areas, or points that may already be marked in the map, like sightpoints, train stations, teleferic stations, etc.

These suggestions are only trying to get the most accurate elevation change possible. But the precision required varies with the way you want to meter your goals. Most of us, do our training on repetitive routes, so it is only necessary to measure elevation once, after that, the goal usually is simply to either climb as fast as possible, or to climb within a given timeframe. Given this, you may not even need to measure altitude while actually riding the bike, you may do it using a car, a motorcycle, an ATV, etc. This allows you to dedicate just a couple of days to measure a set of cue points to construct a personal database for diverse altitudes with high precision for your locale, which may not be readily available for you at the moment.

However, there may not be a necessity for such high precision, specially for longish rides that climb over 500 meters (1640.42 feet). What I say is, 6 meters (20 feet) is almost a two story (or storey, a floor or level of a building) height from the ground which can be climbed in a matter of seconds in a fairly pronounced slope, buy may take so much longer in a not so steep incline, that is, time can be a much more significant measure for goal setting, and clocks are so easy to find...

I agree that GPS may be imprecise, but within a range of 15 meters (50 feet), which represent two minutes from a 45 minute ride, I find it absolutely acceptable, since I rely more on a simple stopwatch than any other method. In that regard, the GPS data that me and my group are gathering in our routes allows us to compare routes, and to roughly predict how difficult should be for us to ride a trail that somebody else shared. For that, GPS is more than enough.

RideWithGps.com does exactly what you want; you can plot a route ahead of time and it will show you the elevation profile.