Sandbox Activity

Introduction
The objective of this lab was to be introduced to sampling by using improvised surveying techniques.

Sampling definition: a shortcut method for investigating a whole population in which data is collected from a small portion of the population in order to get an idea of what the whole population is like.  Sampling from a spatial perspective means that data is collected in certain spots throughout a given area to get a better understanding of the area.  It can be done to create topographic maps, analyze population data, or observe various other types of information. 

Sampling techniques:
-Random: data is collected randomly.
-Systematic: data is collected systematically/evenly.
-Stratified: data is collected systematically, but data is collected more extensively in specified areas. 

Methods
Figure 1 shows the location of the sandbox site, on the eastern side of the Phillips science building on lower campus.  

Figure 1: This map shows the sandbox site location on UW - Eau Claire's lower campus.

The materials for this activity included: a sandbox (approx. 4ft x 4ft), tacs, string, a measuring stick, a field notebook, and a camera. 

Our group chose to use a stratified sampling technique.  We did this in order to get a more detailed survey of the area of interest.  It was a systematic approach, and we just decided to sample the central area of the sandbox with more data collection points.

Using the top of the sandbox border, we set up a grid system using the tacs and string, as seen in Figure 2.  The vertical strings were spaced every 5cm, as well as the horizontal strings in the central area of the sandbox in order to collect the most data points where the landscape had more features/variation. 

Figure 2: This image shows the strings being strung between the tacs that were distributed every 5cm on the top of the borders of the sandbox. 

Our "sea level" was at the level where the grid was strung across the top of the sandbox borders, so all of our measurements were measured in distance below "sea level". Using the measuring stick to measure at the intersection of each string as a point on the grid, each x/y coordinate was measured with a z record as elevation at that point.  This process is shown in Figure 3.

Figure 3: This image shows how the measuring stick was used to measure the distance from the "sea level" to the landscape floor at that specific point. 

One person acted at the measuring stick holder, another read each measurement aloud, and the third person recorded these measurements in a field notebook, which is shown in Figure 4.  This data would then be used later to create a digital elevation map. 

Figure 4: This image shows how each measurement was recorded into a field notebook. 

Results
Figure 5 displays the final result of this activity thus far.  Each point was entered manually into an excel spreadsheet. 

Figure 5: This image contains the final result of this activity at this time: all the measurements within an excel spreadsheet.

Once the group chose the sampling technique, that method did not change throughout the data collection process in order to not have inconsistent data.  This method worked quite well in collecting the data, and the resulting spreadsheet contains fairly consistent data.  One concern that was discovered was that the strings may not have been tight enough to remain perfectly level throughout the grid, so each string was re-tightened to account for this.  Other than that, the preparation for our data collection made the process quite smooth.  As the group proceeded, each member became faster and more efficient until all the measurements were collected.  Roles were even swapped in order to relieve each other of the more strenuous jobs. 

Conclusion
The sampling conducted in this activity was a good representation of the ways spatial sampling can be done on a much larger physical scale and with much larger data and more variables.  This sampling method allowed us to virtually map the sandbox quite accurately with just simple tools and the collection of a couple hundred data points.  This activity is just a small version of how data can be collected for a very large area.  When satellites or other aircraft capture images or lidar data of the Earth which are then used to analyze that area, they are also collecting specific information for specific points on the Earth as we did in the sandbox.  I believe our sampling did an adequate job in surveying the landscape within the sandbox.