Introduction - What Is Scale?

Scale refers to the spatial and temporal dimension of natural phenomena and provides context for observations and measurement of objects, time, processes, and other phenomena (Turner and Gardner 2015). All observations have a spatial and temporal scale. Changing scales allow us to zoom in our out in time and space. In time, this is like looking at a day in hour increments and then zooming into an hour with minute increments. In space, this is like zooming in or out of a google map. The two components of scale are grain and extent (Weins 1989). Understanding how to properly apply scale is fundamental to measuring, understanding, and interpreting the world around us.

Grain is the size or duration of the individual units of observation (Weins 1989). Often referring to a plot size, pixel resolution, or the minimum unit of time from which observations are taken from. Extent is the entire window from which all observations are taken, referring to an area or time span. Extent and grain define the upper and lower limits of resolution, respectively, and are analogous to the total area and mesh size of a fishing net (Weins 1989). Extent is reflected in the total size of the fishing net and grain is reflected in the mesh size. 

Consider the importance of using an appropriate net for catching large fish in a study. To capture large fish we need a large enough net (extent) so that a reasonable number of fish will swim into the net. We also need a mesh size (grain) that will allow the large fish to partially pass through and get stuck in the net. If the net is too small not enough fish will encounter the net. If the mesh size is too large the fish will swim through the net and escape. If the mesh size is too small the researchers will only catch small fish. In order to catch large fish, fisheries researchers need to carefully select an appropriate net, otherwise they will not get the results they desire. This illustrates the importance of selecting an appropriate scale to meet an objective. Misleading results and undesirable outcomes occur when scale is misapplied or ignored.