For our first exercise we were given the task of creating a terrain inside a sandbox in the Phillips Hall courtyard. We were to create the terrain using snow and come up with our own techniques of measuring the elevation of the terrain. We needed to create terrain that included a hill, depression, ridge, valley and plain. After we get our measurements we go on to create a digital model of the terrain in the next exercise.
Methods
First we constructed our terrain by shoveling snow into the sandbox and packing it down into different geographic features that included a hill, canyon, valley, plain, and ridge (fig. 1). The terrain sat below the top of the sandbox with the highest point level with it so we used the top of the sandbox as our sea level.
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| Building the terrain in the sandbox with snow. (fig. 1) |
We then measured out the edges of the box which was 120 cm by 236 cm. we then measured out markers on each side of the box and placed tacks every 10 cm (fig. 2). There was 12 tacks on one side and 23 tacks on the other. We numbered the long side (1-23) and used letters for the shorter side (A-L).
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| The grid we created using tacks and string along the side of the box. (fig. 2) |
Next we used string to create a grid on top of the terrain by winding the string between the tacks. We were short on string however, so we had to measure the sandbox one half at a time. We then went through each point of the intersecting string and measured the height (in centimeters) below the top of the sandbox. One person would use a ruler to measure while another would write down the data in a table (fig. 3).
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| Joe measuring the data points and me recording the measurements. (fig. 3) |
We then took that table of data and created a excel data sheet with all of our z-values being below zero. The numbers were used as the y-axis and the letters were used as the x-axis (fig. 4). The intervals between these points were 10 cm with the the last interval in the x-axis being only 2 cm and the last interval in the y-axis being 6 cm. We chose to exclude the extra length at the ends of the box to create a more perfect grid.
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| Data table. (fig. 4) |
Discussion
During this activity we need to keep discussing and thinking about how we were to go about completing the task using the previous semesters blog posts as guidance. We then had to figure out in the next exercise how to use the data table we made in this part in ArcGIS and put it in a language that could be mapped. To do this we will need to have the x and y axes in centimeters and bring the lowest point of the terrain as our 0 or sea level.
Conclusion
Figuring out how to map a three-dimensional terrain involves a great deal of spatial thinking and coming up with ways to organize the data we were collecting. Finding how to get this data into ArcGIS also had to be a factor when collecting and organizing the data. The next step is to create a elevation model in ArcGIS in the second exercise.
