Welcome to BRENTACOL. This site is an off-shoot of my humble blog where I endeavored to catalog, comment on and provide gradient information for the climbs I do on my bike. I have cataloged the hills in my local area of Rhode Island quite exhaustively. Beyond Rhode Island, I have started cataloging other hills I have done that are either particularly interesting or difficult. Some I have done, some I have not.
As this site progresses, I hope to keep adding hills. If there is a hill in your local area that you think should be listed, let me know. If you can convince me of the importance or difficulty of the climb, I may do it for free. If not, I am always willing to catalog your climb and provide you with a nice gradient map of your favorite climb in exchange for a donation to the site. In addition, the ability to properly generate a gradient map and calculate gradient information is dependent on the data provided by Ride With GPS which is in turn dependent on the information it gets from the National Geological Survey and/or Google Maps. The data is great for some areas, but not for others, and is not always available. If you really want to see what's going on with the site in terms of programming (though I'll also be mentioning new hills here as well), please check out the change log.
How the maps are made
The maps are made by plotting the hill in Ride With GPS, an excellent and free route-plotting site. There is definitely a technique to a plotting your hill well. In some cases, it is helpful to view the map in topographical mode. (In some cases, as with Mount Tom in Massachusetts, it is absolutely necessary, since the Topographical view is the only one that displays the road to the summit.) You may need to experiment some to make sure that you don't get unexpected gradient spikes, and you may need to try other views, such as satellite or terrain mode. Once I have a good RGPS map, I download the .gpx file that veloroutes provides. That file is parsed by my program which then generates the gradient map and stores the relevant information (Average Gradient, Max Gradient, Distance and Cotacol Ranking).
The BRENTACOL system
BRENTACOL is based on the COTACOL system, and is a method for ranking the relative difficulty of various hills. Anyone who has done much climbing knows how difficult it is to make these sorts of comparisons. For example, what is more difficult? Lincoln Gap or Mount Washington. Washington is MUCH longer, and has a steeper average gradient. Lincoln Gap, however, contains the steepest mile of paved road you'll find anywhere in the country. Or in Rhode Island, we have two short but steep hills on the East Side. Jenckes takes more overall effort to climb than Bowen, but I've never seen anyone fall over sideways on Jenckes, which is not a rare occurance on the 30% section of Bowen. (What makes that little sections so tough are the cobblestones that you've just finished when you get to that section.)
So what I'm saying is, take the rankings with a grain of salt. Cotatol averages out some of these things and factors in others, so it adds a valuable tool to trying to judge the relative difficulty of a hill. But your subjective opinion will still be important.
A full description of the COTACOL method can be found (in Dutch) in the book 1000 Hellingen van België, a book which is in some respects the inspiration for this site. To the extent that I was able to decipher both the math and the dutch, the method factors in gradient at the resolution of 100 meters, road surface, and changes in gradient. It does not (since it would be irrelevant in Belgium) care about altitude. Similarly, cobblestones are so rare in the U.S. that I've ignored the road surface factor in my implementation.
BRENTACOL is, therefore, a bit of a work in progress. For now, it is based loosely on Cotacol, but I'll keep tweaking it to get it right. I hope to add a factor for elevation. Road surface will be difficult to automate, since there is no information of that type included in the veloroutes data. However, I may add a simple "road condition" field, and may add some sort of rating-bump for hills that feature difficult surface.
For the BRENTACOL logo, I've chosen the image of the mountain goat, a classic slang name for climbers