1) What does the DEM layer show? What is the cell size and how do you know? Why is the cell size important?
The DEM layer shows an elevation model for the Three Sister’s region of Oregon. Each raster cell contains the elevation in a 10 meter area; ArcMap maps the elevation data to a color-ramp so that it can be visualized. I found the cell size by looking at the file title. I confirmed this by looking in the raster layer properties in ArcMap where is gave the exact size as 32.79768284 feet. The cell size is important so that the change in elevation can be correctly correlated to distance.
2) Why reclassify water in this way? How will the value of the water affect the resulting cost surface?
In this scenario we want travel across water to be prohibitively expensive to travel across. By reclassifying it as binary values of 0 (no water) and 100 (water) the areas with no water won’t affect the cost of the land travel, and one cell of water will be 10 times more expensive to travel across than the steepest slope–guaranteeing that the computer will (most likely) find a path that doesn’t take the mushroomer through the middle of a lake.
3) What other data could be used to generate a cost surface? Do you think our slope/water cost surface is the most realistic representation of how difficult it is to travel from one grid cell to another? Why or why not?
Some other data that could be used might be vegetation cover, road or trail locations, slope direction (uphill vs downhill). I think that slope and water is a good approximation of travel difficulty for this scenario. I wouldn’t want to try and get too scientific because the project is time sensitive. If too much time and effort is spent getting an exact least cost, which is time wasted looking for the lost mushroomer—especially considering that a human won’t necessarily take the least cost route.
4) What does the attribute table of the Observer Points raster tell you? How would you determine which cells can be seen from which lookout?
The attribute table tells me which field belongs to which observation point, as well as where they overlap. I used the name of the observation point, and I double checked by selecting each field and making sure that I was correct.
5) Based on the results of your observation points analysis and the least cost path you generated, which lookout would you recommend the Forest Service use to the mushroom hunter? Why?
I would recommend that they use Lookout 1 because it allows for a larger viewshed in the direction that the mushroomer was headed (Nash Lake).
6) With reference to each map, explain which areas you would prioritize in searching for the mushroom hunter. Make sure to also explain the steps you took to conduct your analysis, including any limitations or caveats of the techniques you used.
Based on the information gathered from my analysis, I would recommend that ground searches focus along the computer-generated least cost path, as well as the neighboring valleys to the east of Cougar Reservoir. Someone should be sent to ‘Lookout 1’ and scan toward the east. Additional searches should be sent to the valleys that the Lookout 1 cannot cover (the two branches forming Horse Creek).
The least cost path that the computer chose is helpful, but does not take into account the decisions that our mushroomer would be making as she traversed the landscape. For example, the least cost path immediately goes up a steep hill in order to access the ultimately cheaper neighboring valley, but if she chose to be dropped off in the more southern valley, we might assume that she meant to travel up it toward Karl Lake, which would change the predicted least cost path. Some other questions: Would she avoid trails and roads in order to locate the rarer mushrooms? Was she heading for a specific trail that would take her to Nash Lake but took a wrong turn? How many days was she planning on being gone – which would help us know how circuitous of a route she might have planned on taking.
The observation fields do not take into account the forest cover. I tried to show that on the map with the green and white coloring. All of the area that the hiker is probably lost in is covered in forest. Hopefully she will start a fire and the lookout might be able to see it and point the ground search in that direction.
