Navigating the Spearhead Traverse
2. Propose the Best Route for the Spearhead Traverse
Huts
- The proposed locations for the new huts for the traverse are all displayed on Google Earth images at The Spearhead Huts Project. Using these images as guides the huts were each added as individual new point feature classes on top of the DEM. The points were added on top of the DEM because it most closely resembled the Google Earth images and thus it was the easiest layer to match up with those images. Personal experience on the Spearhead Traverse helped to inform this process as I have a good sense of where these proposed hut locations are.
Cost Surface
- Reclassified the PADS as a step to create a friction surface for travelers. The point of this component of the cost surface is to suggest a route that is the safest and so high danger areas were presented as being high cost areas to travel through. PADS categories 2, 3, and 4, were reclassified as 10, 75, and 100, respectively. PADS category 1 remained at a value of 1 to mean that traveling in "very low risk, totally safe" zones were at relatively no cost to the travelers.
- Reclassified the landcover classes as a second step to create a friction surface for travelers. The point of this component of the cost surface is to suggest a route that is the fastest and most efficient and so landcover categories that are decidely more difficult to navigate through were presented as being high cost areas to travel through. Landcover categories Sparse Trees, Open Trees, and Dense Trees, were reclassified as 5, 10, and 20, respectively. The category Open Land was reclassified to be 1 to mean that traveling through open land is at relatively no cost to travelers.
- Using the 'Raster Calculator' tool the two above friction surfaces were combined into a usable cost surface (henceforth known as Avalanche Landcover Cost Surface (ALCS)).
Path Distance with the Cost Surface
- The final step was to calculate the cost distance from one end of the traverse to each one of the huts in succession and ending at the other end of the traverse. The 'Path Distance' tool allowed for a new cost surface (henceforth called 'path distance surface') to be calculated using the ALCS in addition to the terrain of the Spearhead Range described by the DEM. A path distance surface had to be created from each of the points along the traverse (the start/end points and the huts). The use of the tool is depicted below.
- The center of each path distance surface was entered as the input feature source
- The ALCS was entered as the optional input cost raster. This is a key component to the use of this tool because it means that the first created cost surface will be used in the final analysis.
- The DEM of the Spearhead Range was included as the option input surface raster. This ensures that the distance and elevation changes were included in analyzing the cost path. This aims to make the proposed route energy efficient instead of steering travelers towards intensely steep slopes.
- The optional vertical factor parameters were based around the DEM as well. The angles of +/- 60° were set as maximum and minimum slope angles that could be crossed and the vertical factor (relationship between cost factor and vertical relative moving angle) was set to be linear. This means that traveling up a 60° slope is the most costly terrain to cross, traveling across a surface of a 0° slope is not costly, and traveling down a slope of 60° is the most energy efficient.
1.
4.
3.
2.
The path distance surfaces from each point. The point the path distance surface originates from is drawn as red with the other huts or start/end points drawn in green. The darker the shade on the map the less costly it is to travel there based on the ALCS and the terrain as described above.
Map 1. - Whistler Symphony Ridge Start Zone
Map 2. - Russet Lake Hut
Map 3. Mt. MacBeth Hut
Map 4. Mt. Pattison Hut
Cost Path
- With all of the path distance surfaces created the cost paths could be created. The cost paths were made using the path distance surfaces as the cost surface rasters.
- The proposed route is displayed below as a blue line over the ALCS. The huts are circled in a light blue for ease of identification. A more polished version is displayed in the Results Page.
