Sunday, December 26, 2010

On Finding Ski Terrain

Recently, one of my Facebook friends who was following my regular postings of our ski days, asked how we found so many great runs and were we using Google Earth. The short answer is yes and no, and the long answer, well, that's the subject of this blog entry.

Finding good ski terrain requires a whole mish-mash of skills and knowledge that generally takes years to acquire - if it is acquired at all. First, you need to have a good handle on the weather, the past, the current, the forecast as well as general synoptic trends. Second, you must be able to read a map really well. Third, that map reading ability must translate into the ability to efficiently navigate mountainous terrain, and fourth, you must be willing to break a sweat and explore a little.

Synoptic weather patterns will tell you which areas, generally, receive more snow. Even in a relatively small area like the West Kootenays, precipitation amounts vary. The Rossland Range gets less of the white stuff than the Nelson Range. And, within the Nelson Range, the east side of Kootenay Pass will have less snow than right up at the Pass. The Kokanee Ranges do well for snowfall, while the Valkyr Range gets less. The storm track, in winter, runs a little north, so northern areas, like the Goat and Nakusp Ranges will often pick up more snow than ranges further south.

Moving from large scale synoptic patterns to day to day weather, things like wind strength and direction, cloud cover, presence of inversions can help you work out which aspect is going to have the best snow on any particular ski day. If it's been sunny with an inversion, you can pretty much rule out south or west aspects. Artic highs generally blow in with strong north winds, scouring north aspects so you'll have to look for either well protected north slopes or work other aspects. The best way to keep track of day to day weather is to keep your own weather log.

Thirdly, you MUST be able to read a map. A lot of people are hoping Google Earth will save them from learning to visualize a three dimensional image of terrain from a two dimensional map. But Google Earth actually depicts slope angle, something that is critically important to a skier, relatively poorly. Google Earth employs a digital elevation model to generate a 3D image from 2D photos so the quality and accuracy of the resultant 3D image depends on the accuracy, completeness and comprehensiveness of the digital elevation model used. Currently, Google Earth depictions of slope angle are not nearly as accurate as an experienced human user interpreting slope angle from map contours, particularly if the user has access to 20 metre TRIM data.

Being able to visualize three dimensional terrain at home from a map is of little use if, once in the field, you are unable to identify landmarks, locate terrain features and handrails, and efficiently navigate to your chosen destination. Blindly following a series of GPS waypoints plugged into your handy "turn off your brain" GPS does not count. Anecdotal as well as experimental evidence shows that people who use a GPS to navigate make more navigation errors, take more time, travel longer distances and take more stops than people navigating by "old-fashioned" methods such as using handrails, backstops, checkstops and other terrain features to find their way.

Finally, and probably most important, you gotta go out on a limb and push into terrain that is unknown to you. Sometimes everything comes together, you pick the perfect slope, with an ideal slope angle, with just the right aspect and vegetation coverage to suit the current, past and forecast weather conditions and you find some great skiing. Other times, you'll have a washout. The slope you thought was good was too steep, too shallow, too densely treed or facing the wrong way, and nothing seems to go right. What you do then is go home, think about what worked and what didn't work, what erroneous assumptions you'd made and you refine your criteria for next time. Most of us, learn the most important lessons when things don't go exactly as planned. So don't curse a wasted ski day, think about all the things you learnt that will help you make better choices next time.

 When it all comes together.

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