This exercise revolves around using a sampling technique to create a small-scale digital elevation surface derived from a sand-box. Sampling is a quick and effective method for investigating an entire population of a specific area. The process involves collecting data on a small section of a whole sampling frame, and in turn, it can assist in configuring the rest of the picture.Various types of sampling techniques include:
- Systematic Sampling (Point, Line, and Area)
- Random Sampling (Point, Line, and Area)
- Stratified Sampling (Systematic, Random)
- Cluster Sampling
- Multistage Sampling
After choosing one of the sampling techniques, the objective is to construct a Ridge, Hill, Depression, Valley, and Plain by utilizing the sand (seen in Figure 1 below). The final process will be mapping out the elevated surface using the original survey technique.
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| Figure 2 displays the features mention above. |
Methods:
Group two chose to use the systematic sampling technique due to its even distribution of various points, making the Digital Elevation Map more accurate. Methods similar to this technique are.
The location of Group Two's sample plot was located east of Phillips hall right off the other side of Roosevelt avenue. The area was approximately 30 meters from the loading dock, and in the middle of the three sandboxes. Group Two used a meter stick, strings, and tacks to create an accurate and evenly dispersed grid.
The Group made a total of 23 points on the Y-axis, and 23 points on the X-axis spread out at five centimeter intervals as seen in Figure 2 below.
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| Figure 2 displays the first half of the grid with lines parallel to the X-Axis |
Next, the group decided sea level would equal the lowest point of their Digital Elevation Model. Then they created a table with three columns labeled X, Y and Z. The elevation (Z) was recorded by measuring the distance from the sand to the string every five centimeter interval of the x-axis and y-axis rounding to the nearest millimeter. Once group member measures each point, while another records the data. The group choose this method because it was quick and effective.
Results/Discussion:
There were a a total of 576 points recorded on the grid for group two. The range of of the sample points varied from a minimum of 4.5 cm to 19.6 cm. The mean was 12.8 cm with a standard deviation that comes out to be roughly 2.81. Group Two found that the systematic method was closely related to the sampling, and would have not chosen another method. Therefore the group stuck to the original plan the whole time. The only problem this group found was losing track of which point was being measured. However, it was an easily fixed by simply restarting the measuring from the beginning of the row.
Conclusion:
The systematic sampling technique utilized by group two relates to the definition of sampling because they were able to investigate most of the population. However, rather than doing a small section of a sampling plane the group did the whole thing. Sampling is used in spatial situations because it nullifies any biases one would have while collecting data. This activity related to sampling spatial data over larger areas because if you can sample a smaller area you can do the same technique with a larger one. This group found that their survey did an exceptional job of sampling the area within the sand box due to the widely distributed elevation of the points properly representing its features. This survey could be refined by adding more points. This group also could have found a more precise mean of measuring the elevation due to the meter stick pushing the sand down a different amount every measurement.
References:
"Sampling Techniques." Sampling Techniques. N.P., n.d. Web. 09
Sept. 2017. http://www.rgs.org/OurWork/Schools/Fieldwork+and+local+learning/Fieldwork+techniques/ Sampling+techniques.htm
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