Topographic Maps and Digital Elevation Models

Chapter 6 Topographic Maps and Digital Elevaton Models 117
7. Where is the magnetic north pole today? Magnetic north is always on the move. The Canadian Geologic
Survey has set up a nice website (gsc.nrcan.gc.ca/geomag/nmp/northpole e.php) showing the magnetic north
pole's current and past positions on its journey through northern Canada. It explains why variations occur on
daily and yearly time scales and projects the future locations of the magnetic north pole. It is worth taking a
moment to check out this web site.
In Greater Depth
8. Plan a hiking excursion: British Columbia offers some of the most rugged scenery in North America. If you like hiking,
leafing through a stack of Canadian topographic maps will inspire daydreams of amazing wilderness experiences (if you avoid
the many logged out areas, that is!). Figure 6.20 shows a portion of the Wells Gray Provincial Park in central BC This park is
in the Cariboo Mountains, which are part of the Columbia Mountains. The blue lines and numbers define the I-km UTM grid.
The map symbols are similar to those of USGS maps (Fig. 6.10); the actual map key is handily printed on the back of the
original map.
Let's say your goal in visiting this part of the park is to combine geologic exploration with back-country hiking. To get there,
you portage 13 km from a lake to the south and paddle some 25 km until you reach the end of Hobson Lake, the large lake
shown in the southwestern corner of Figure 6.20. For more information and photos, visit www.wellsgray.ca.
a. First off, most of the map area is covered in green. What does this mean?
b. Your goal is to climb the large hill with a number of lakes on its top (near "FP GP"). What is a representative elevation of
the area with the many small lakes? What is the height of this area relative to the lake that you arrived on?
c. To get to this hilltop, you need to beach your canoe and hike. Based on the map symbols, what is the landscape like at the
northeastern end of the lake?
Do you think it would be an easy hike across such a landscape? Why?
d. The edges of established forests, such as along lakes or highways, often SpOt1 a dense undergrowth. Away from the edge,
the undergrowth tends to disappear and hiking is easier. In anticipation of this and other problems that can effectively block
a path, use the following guidelines to draw three possible paths leading to the lake area on top of the hill. Label each path l
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Path A: Take the shortest route from the lake shore to the hillside. Continue to the hilltop with the lakes via a route that,
while it may be long, follows the gentlest slopes. The goal is to avoid scaling a cliff.
Path B: Take the canoe up East Creek (which drains into Hobson Lake) and land where you won't have to worry about
marching through a swamp and where you get the most direct route to the lakes without climbing unnecessary elevation.
What is the average slope of your path once it starts up the hill? Express the result in meters per meter.
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Path C: Take the canoe up Hobson Creek as far as necessary to avoid swampy land and to gain access to the gentler
slopes leading to the toe of the hill near the letter "I." Avoid any closely spaced contours that indicate inconveniently
steep slopes, and avoid climbing unnecessary elevation on your way to the lakes on the hilltop.
Calculate a typical slope of this path once it starts up the hill from near the letter "1." Express the result in meters per meter.
e. Find the peak with the highest elevation on the hill with lakes and mark it with an "X." What is its elevation?