When I first bought a GPS system it was all about not getting lost. I was riding some trails that were not well mapped and the GPS helped me get a birds eye view for where I was going. Once I became familiar with the trails and settled into a regular rotation, the GPS became overkill and I stopped carrying it.
Well, Dr. P (a regular riding buddy and one time GC contributor) received a new GPS system from his lovely wife this past weekend for his birthday. We took it out on a trail that we have ridden a hundred times. Now Dr. P is a data guy. Once he got that bad boy back home he instantly downloaded the data and began slicing and dicing it like crazy. He dumped it into Excel and began calculating the tangent of the cosign of the hypotenuse of the derivative of 2/3 of a rhombus to the 2nd power.
Whoa...whoa...whoa...Dr. my head is spinning...
There's got to be an easier way. Well the software didn't help much since it was largely built for GIS users or cartographers. So we turned to the 'net to find out the formulas for such common measurements as hill steepness or "grade."
Grade is the easy one. It's simply:
grade = vertical_climb / horizontal_distance
Grade is reported in the form of a percentage. But once you get the number, now what? I really like Bike Hudson Valley's explanation:
0% grade is exactly flat (and a negative grade, less then zero, is downhill).
2% grade does not seem very steep, but it's enough to substantially reduce forward speed, and for most riders it will absorb more than half their power output.
6% grade is enough to cut speed to well under half, and absorb more than 80% of a rider's power output (leaving less than 20% to fight air resistance and rolling friction).
10% grade, and anyone who is not a fit and frequent rider is off their bike walking -- and anyone who is not a racer is reaching for all the extra power they've got.
Still, there are nuances. These numbers must be put into context and Bike Hudson Valley tries to do just that by explaining the tricks to computing total vertical climb and by proposing a total "hill index" for the entire route.
Once this data was surfaced it really gave me a new perspective on my "home" trail. For example (some of the locals may appreciate this one), I learned that the climb up to the Cricket Fields on the Colts Neck loop trail is a grade of 12% (you know...where you cross the stream...navigate the ruts of mud...finagle the parallel roots, while setting yourself up for the perpendicular root...around the bend...and mash up to the cricket fields). While not a particularly long climb it is fairly steep and the ease at which you climb is a good indicator of your overall fitness for the day.
The bottom line is that I will no longer look at my GPS as simply a mapping tool. Instead it will also be a tool to help me compare and contrast my rides across all of my favorite trails. Now I can't wait to measure the grade of the red loop climb at Greenbrier and calculate the hill index for Fountainhead.
Although, I tend to be more of a right-brain type than left, I must say that the good doctor is sometimes correct. Data, while interesting, can sometimes be useful.