Geography Reference
In-Depth Information
Human Activity, Cost, and Distance
Life forms on our planet may be divided into plants and animals. A major difference between them
(although there are exceptions) is that plants do not move (much) and animals do. In fact, for human
beings in particular, moving themselves and their artifacts, such as clothing, weapons, and stereo
equipment, is a major activity.
Frequently, a major concern about a given human activity is its cost—cost in terms of energy, time,
money, fuel, suffering, or other parameters. Moving from one location to another is a frequent human
activity and one whose cost we often want to minimize. We usually move because we want to be in a new
location or leave an old one for some reason. (There are exceptions to this: a walk in the woods for soul
healing, a jog for exercise.) The subject of this discussion is using GIS to
Reduce the cost of going from one place to another
❏
Lower the cost of transporting artifacts
❏
Minimize the cost of building linear structures, such as roads, bridges, and tunnels
❏
The costs of moving from one place to another can be complex to calculate. In cases where the distance is
far, the trips are repeated frequently, or the cost is critical (as in the cost in time of getting an ambulance to
the scene of an accident), it may well be worth doing the computations. In this discussion, you will learn
how to deal quickly and simply with the complexity of performing the “cost of moving” calculation.
What are the factors that determine the cost of moving things, including ourselves? The one that perhaps
comes to mind most quickly is “distance.” It costs more to go from Punxsutawney, Pennsylvania to Red
lands, California than to go from your living room to your bedroom. Or from your home to your office.
We begin with a consideration of distance—distance of the simplest sort: straight-line distance (on a
Cartesian plane) from any point to a given point.
Euclidean Distances on the Raster
Distance is measured between two points. The two points used when measuring distance
on a raster (or grid) are the centers of two specific cells. That is, in the case of the raster, the
measurements are made from cell center to cell center. See Figure 8-9.
If the cell size is 50, the distance shown would be 200, spanning all or parts of five cells.
For another example, if you had a raster that had cells of size 10 and 1000 columns, the longest east-west
distance measurement would be 9990.
FIGURE 8-9 Distance is measured
from cell center to cell center
Search WWH ::
Custom Search