Activity #1: Terrain Survey

Introduction



This activity had several objectives. Not only were groups tasked with creating and surveying terrain  in sand/snow boxes, which would introduce students to bringing real world data into a computer without the use of digital tools, but also forced students to use critical thinking strategies to accomplish the assignment. Students were given little direction on how to do build and survey the locations, so working together with groups was key to finding the best way to manually survey the locations.

Methods

The activity called for groups of five to build a terrain that included a ridge, hill, depression, valley and a plain in the planter boxes located in the Phillips Hall courtyard on the University of Wisconsin- Eau Claire campus. We had access to meter sticks and tape measures, as well as any other equipment we had ourselves.

It was originally difficult to find a time to meet, due to schedules and sub-zero weather. Much of the week had a wind chill advisory for our area. The first day we were going to meet ended up snowing heavily, so we postponed until Saturday.

First, we decided that we would set "sea-level" at where the frozen dirt was (beneath the snow), and build our terrain on top of that. After excavating the snow, however, we found that the dirt underneath was not at all level (Figure 1). Instead, we decided to set our temporary "sea-level" at the rim of the box. This would mean that the depressions and valleys would get negative values, but we would be able to set "sea-level" to any point below our lowest point later, allowing us to use only positive values when importing data into ArcGIS.

Figure 1 - Non-level initial sea-level

 Once that was decided, we filled the box back in with snow and leveled it off. From there, we built the terrain. The valley we carved into the snow meandering across the box. We put in a ridge in one of the corners, a depression in a different corner, and two hills on opposite sides of the valley. We left one corner open as a plain (Figure 2).

Figure 2 - Finished terrain



Figure 3 - Measuring and marking our grid

Once the terrain was sculpted, we needed to decide on a coordinate system. We settled on grids that were 8x8cm. This was because the x-axis (the shorter end of the rectangle) was divisible by 8 (112cm). The y-axis could not divide by 8, but we simply ignored the last row of half squares. In the end, our coordinate system ended up being a 29x14 grid of 8x8cm squares. We measured the distances and marked them on the wooden frame of the box (Figure 3).

Next came the difficult part. We had to figure out how to survey the features. With us, we had two meter sticks, string, pencils and pens, thumb tacks, and a notebook. The biggest problem we encountered was that our features were built higher than the rim of the box. This meant that putting anything level across the box to form the grid would ruin our terrain.

Figure 4 - Setting up string grid

Our original idea (when we were still planning on using the dirt as the base ground level) was to have a grid of string stretched over our features, who's highest peak would not have passed the top of the box. This obviously wouldn't work.

We settled on allowing the string to lay on the terrain, following the curves (except of the deep valley, which the string bridged across). Figure 4 shows process of setting up the string and figure 5 is the finished product.







Figure 5 - Finished sting grid

To survey, we used the meter sticks and measured (in cm) the highest point of every square. Many of the squares had no positive or negative elevations, and so we didn't need to measure. I didn't get any pictures during this portion of the exercise because we were all active at the time. After being out in the frigid weather for several hours, we wanted to finish as quickly as possible.











Figure 7 - Data organized in a way that could be
imported into ArcGIS

Once we collated our data into excel, we could visually get an idea of how it would look (Figure 6). The problem was that having the data organized like this was pretty much useless. Instead, we needed a table that had the x,y, and z values in separate columns (Figure 7).




Figure 6 - Original raw data

















Figure 8 - Survey data
with all values
increased by 12.

The last thing we wanted to do before bringing our data into ArcGIS was to change where sea-level was. We thought it would be easier to deal with the data if we did not have to worry about negative numbers. To change this, we simply added 12cm (our lowest measurement was -11cm) to all measurements. Our "sea-level" was 12cm below the edge of the box. Figure 8 shows this transformation. In the 'z' column, anything that shows '12' was actually level with the sandbox rim.














 

Discussion

Critical thinking and teamwork were very important during this exercise. From looking through the blogs from last semester, we had a general idea of what and how to accomplish the goals. But this still left a lot of wiggle room. We encountered several issues and problems (only one of which was the unforgiving cold), but working together we were able to gather our data.

In the next post, I will be uploading this data to ArcGIS and trying to create a 3-dimensional image of our terrain. Hopefully our survey method worked well enough.

Conclusion

This lab did a good job of not only getting us used to thinking critically and do some problem solving, but also forced us to think spatially. It seemed like after every step, there seemed to be some little problem in our way. We would brainstorm and decide the best solution. This even included the best way to write down numbers while keeping fingers warm. I'm looking forward to completing the next lab and see how accurate our data ended up being.