Hey gang. Do you know of an iPhone app that will display real time the Grade-% of the current workout (bike ride)? I know some Garmin 500s or 800s can do it but I’m just thinking about an app if I can avoid buying one of those just for that Grade-% reason. Have a great event if racing this weekend! :O)
The garmin edge (500 series and up) use a barometric altimeter to get real time elevation data, then calculate grade. I suppose you could get that from an iphone app, but it would likely need to use GPS elevation data…which isn’t that reliable.
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I’d be happy to get started with a GPS-based value even if it’s not that reliable. We’ll see what the gang has to suggest! I’m pretty sure many have had this need and perhaps got started with an iPhone GPS one… we’ll see! :O)
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If it isn’t accurate (reliable), why would you want it / what is the point of seeing it?
I strapped my Garmin 310 to my kayak and went and paddled around a lake earlier this week. I’m pretty confident due to the laws of physics and fluid dynamics, that I did not experience the 207’ of elevation gain and descent it said I did 
I think people tend to forget that just because something is displayed in a digital form on a screen that it is not necessarily accurate. This is demonstrated by all of the “The certified course I ran Saturday wasn’t accurate! My GPS said it was 0.2 miles long” threads we see here on a regular basis.
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So true, my 310 is way off. To the point that I wish it didn’t even display it on garmin connect or strava. Makes it hard to compare rides. I think Stravas corrected values are even more inaccurate sometimes too which is obnoxious… especially when i start and end at the same place and I have an elevation gain or loss of hundreds of feet.
well, doesn’t look good then. :right? I guess I shouldn’t believe what I see in the movies… 
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Dont need gps data for this. Any smartphone should be able to figure out the grade in real time via their set of accelerometers. Assuming you mount it level or solid ly then zero it.
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I’m not familiar with the accelerometers in smartphones, but I very much doubt they will work. The iBike has a tough time and that is with an accelerometer and filters specifically designed for the purpose.
Instantaneous grade isn’t going to be even semi accurate with GPS… but usually decent averaging long distances. Barometric will be better over short distances, but on a long climb it will often be worse than GPS.
Which is why I ditched the iBike. It uses a barometer to adjust the tilt, and I was getting 5% scatter for grade on long climbs… too much.
grade % is something better left for calculating after the fact. Are you looking for this out of curiosity or do you think it is something you would actually use while riding?
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Elevation profile would be useful too. I’m just trying to maximize the iPhone without entering in the Edge 500/800 territory. Perhaps as previous gang members have said, the fact this mini-data processing unit (iPhone) is missing the key component to measure elevation. I read many articles about the 910xt some time ago being inaccurate on that measuring as well (even though is advertised as capable of compared to say the iPhone/Android mobile devices).
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maybe look at getting somthing slightly older, I have seen garmin 705’s go for around £70 on ebay, they do grade, have the barometric sensor, Ant+ for HRM’s cadance power etc. oh and have inbuilt OS maps and routing for if you ever do get lost.
I got miy 705 for £115 with HRM, bit clunky in comparison with the new stuffbut for the price… one of the best things Ive bought!
But if just have to know in real time, and appearance is unimportant…
http://bicycles.stackexchange.com/questions/10376/is-it-possible-to-estimate-road-grade-while-riding
That bubble meter in the second post is pretty much the bomb.
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yep - there’s technically no real ‘spot’ grade in real time, since you’ve got to calculate ‘rise over run,’ and get your grade *per *a given distance traveled. so i think even the very best/most accurate/fastest calculation of grade would by nature always have a lag, wouldn’t it?
Well, one could imagine a bike computer that measures angle directly (as in, you could just tilt the bike up without riding it and it could tell you ‘grade’, just like a digital level). The slightly tricky part would be calibrating it after installation, which would entail measuring the accelerometers with the bike facing both directions in the same spot to get the offsets zeroed.
Would it be aero? 
Same with speed Mike!
Real Time speed
vs
Point-A minus Point-B
--------------------------- = Speed
Elapsed Time
But I see your point
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Out of total curiosity, what is your interest in knowing the current grade?
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Effort related. I’ve heard my friends saying ‘this hill is % x grade’ while using these high-end Edge units (maybe theyade it up knowing that value while riding -not after the fact at home comfortably sitting). I recently got an iPhone and after managing to display most usual ride-related values (speed, hr, cadence, hr-based power -oh yeah, not owning a PM yet, etc) I (naively) thought incorporating grade was not going to be difficult but perhaps it actually is insane. I agree we can start a debate on whether or not is useful to know such value while riding compared to post-analysis!
:O)
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I would say that, in situ, % grade is not a very good measure of effort … but can be used after the fact - and in combination with other ride data - to characterize the difficulty of certain route segments. On one of my regular routes, there are multiple sections that have channeled air currents based on the topography. One long section has a sustained grade of 4-5%, but due to the prevailing wind direction I can ride up it in a relatively large gear without an appreciable increase in power. Other sections on that same route have very similar grades, but would require a much greater effort to achieve comparable results.
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Ok. See what you mean man. Similar to using HR to ‘extrapolate’ the power values which is just an approximation since other variables affect such measurement if following that route. Got it!
Before I owned a power meter I used to use grade a lot with my old Edge 305 (especially when riding in the mountains). If I was working really hard and only going 25km/hr it would be useful to know that I was climbing a 1.5% grade that just happened to look really flat. With a power meter all that matters is wattage.
I still use grade a fair bit when I am riding my rain-bike since it has disc brakes and I can’t put my powertap wheel on it. Even with the barometric altimeter in the Edge 510, the real-time grade reading is questionable. I’d say it is normally accurate within plus or minus 2 to 3 percentage points. But sometimes there are insane spikes. For example I will be climbing a 15% grade and it will shoot up to 25%, then down to 12%, then back up to 25%.
Will the iPhone app display elevation? If so, you could probably get the same feedback by observing if the elevation number is increasing or decreasing.
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so i think even the very best/most accurate/fastest calculation of grade would by nature always have a lag, wouldn’t it?
The iBike is the best thing you will find for instant grade. It uses accelerometers and it needs to be good because it uses this data to calculate power.