Fixes some crashing when viewing the map, made graphs more visible, improved power measurement for Clydesdale riders.
In this update, I have added a total power output for the ride in watt-hours. This technically could be used to determine how many calories that one has used while riding.
While this is useful data, I don’t think that my application is the best thing to determine tailored calorie burn data. I would strongly recommend “LoseIt” if you want that data. It is what I use for calorie and weight monitoring.
The other thing that I added was total elevation. For those who have been using the iPhone for a while, you are aware of the issues with getting accurate altitude data. You might not be able to get exact elevation gained on a short-flat ride, but if you are going for a hill ride, or doing some serious climbing you should get decent overall numbers. If you want to see how to get the best possible GPS tracking data while cycling, check out my earlier post on what to turn off to get perfect GPS tracking on your iPhone.
Other improvements are mainly in the area of power. Average, peak, and watts per kilo should have improved dramatically, and as a result the GPS accuracy should have improved due to the reduced stress on the CPU.
One issue is that I have renamed the Google Spreadsheet that CycleMetrics writes to, so you may have two files. I hope these updates improve CycleMetrics’ usefulness for you! Good riding!
Some time ago I had a good friend explain to me how GPS works. It seems that it uses the CPU to create a mesh of the signals from the various GPS satellites tracking around the Earth. The signal is very faint, so it has to use DSP to improve the quality of the signal, and then begin to tighten down the mesh until the grid square that the device is in is small enough to provide reasonable accuracy. To obtain altitude, the device has to find a signal from a 4th satellite that is at something of a horizontal to you to figure out how high you are relative to sea level. Finding this satellite takes a while which is why current GPS devices are so terrible and take so long to determine altitude.
The iPhone, and other phones, get a boost in speed by using the cellular network to get a rough location, and to download the locations of the satellites instead of trying to get it from the satellite network itself. This is called aGPS, which is what the iPhone uses.
Another piece of information I discovered with a few friends a while back was that when the iPhone is either on a congested Wi-Fi network, or is hunting for Wi-Fi, in addition to draining the battery, the performance of the CPU is degraded, especially on 3D gaming.
Recently on my last ride, I put these things together and turned off 3G ( leaving EDGE on ), turned off Wi-Fi, in addition to disabling push notification and setting fetching for email to manual, turned off bluetooth, and disabled auto-lock. This left my iPhone in a near airplane mode state. After my ride, I reviewed the map and to my surprise all of the inaccuracies I was blaming on my iPhone having subpar GPS went away. The tracking was perfect, the best I’ve seen as well as having fairly little battery consumption. I’m not sure what impact 3G has on the CPU, but it is likely significant as I had done some of these other things in the past and not had such rock solid GPS tracking before.
I think I’ve found a new riding configuration, if only Apple would update the settings application to give me custom settings bundles so that I could drop it into my riding configuration with one tap. Maybe for iPhone OS 4.0?
I had always known about how Lance Armstrong continuously advocates riding with a higher cadence and in a higher gear for maximum speed on a bike. I never really appreciated how that worked until today.
I was on one of my usual rides today, but I had left my bike in a higher gear than I usually ride. I decided to stay in the gear throughout my ride. What I found is that I dropped 0.2 watts per kilo, and was off about 40 watts from my typical average power output. It could be that it was cold, but I don’t think so. I have done that ride many, many times and I am typically at around 2 watts per kilo or a little better and 200 ~ 220 watts average. I dropped to 1.6 watts per kilo, and 175 average or so.
What I expected was a minor drop in watts per kilo and average, but what I didn’t expect was the magnitude of the drop in average and max output. On my next ride, I’ll drop into my usual gear and see how it compares. It is really cool to have access to all this data.
Last night the spurious power readings that occasionally occur were bothering me, and I think I can fix it.
Mostly the problem is distinguishing stopping from accelerating. Generally to the device they are the same, however I am going to start testing a fix that I hope will make the max power reading more accurate.
If you want to get the most accurate reading however, before I deploy the fix, here are a couple of tips.
1 ) When stopping, stop gradually ( I know that this is hard in urban riding )
2 ) At the end of your ride, when you are pulling your phone out of your jersey, bring it out slowly, so as to not create any power surges.
Hopefully I will have the fix out soon.
Happy Turkey Day!