Exercise 1: Terrain Survey

Introduction

The first assignment of the semester had students create a miniature landscape out of snow and then survey the data to create 3D terrain models. A number of sandboxes located in the Phillips courtyard were the areas of interest chosen for this exercise. Students were split into groups of 4 or 5 and sent out without any specific instructions for measuring the terrain, which lead to many different surveying and digitizing techniques throughout the class. 

Methods

The first order of business was deciding how to arrange the landforms within our sandbox. Each group had to incorporate a ridge, a hill, a valley, a depression, and a plain. We decided to arrange our landforms in a way that made the most geographical sense; we created a U-shaped valley opening away from the hill as if a glacier once carved its way through, we created a ridge which connected the hill to another point of elevation, we formed a depression(lake) at the bottom of the hill, and smoothed out some plains after the location where the glacier retreated. Instead of just throwing each of the five landforms in a sandbox, we felt that we had truly created a realistic physical landscape. 

Constructing the landscape

The next task was to decide on a coordinate system to use in order to survey the terrain quickly and efficiently. Since our landscape included some steep changes in elevation, we chose to create a grid using 5cm increments on both axes as opposed to a less detailed increment of 10cm. Thumbtacks were inserted along all sides of the box in 5cm increments and labeled accordingly. String was stretched across the box to each thumbtack resulting in a grid of squares 5cm wide. The width of the box was approximately 110cm(22 zones) and the length of the box was approximately 240cm(48 zones), which gave us 1056 zones or points of elevation to collect. These zones were then replicated in a spreadsheet and printed out for elevation data collection.

Once the grid was constructed, elevation data could be measured. To collect the elevation data, one person simply lowered a meterstick into each gap and another person would read out the measurement(the point on the meterstick that the string lined up with) and record it onto the spreadsheet. Working in pairs, our group had two teams consisting of a surveyor and data recorder working simultaneously. Unfortunately, the weather did not make data collection very easy for us. Temperatures were rarely above zero for the entire duration of this project and constant wind made collecting the elevation data extremely difficult and time consuming. All 1056 points were eventually recorded after working in hour long chunks throughout the week. At the end of each data recording shift, we would cover the sandbox in large trash bags to avoid having our terrain manipulated by the elements. 

All 1056 zones were measured by hand

With the table complete, we could finally go inside and try to recover from the Siberian temperatures of the courtyard. The numbers were crammed into the computers and translated into a 3-column table consisting of the x coordinate, the y coordinate, and the depth of each zone. This format would allow us to seamlessly bring the numbers into a GIS and digitize our work the following week. 

Discussion

I learned a lot from this first exercise; it was open-ended and challenging and required many ideas from different people in order to complete it. Everyone in our group had their different strengths and whether we were surveying, creating the coordinate system, or entering data, there was no doubt that we knew exactly what we were doing. Our group worked great together and although some members couldn't participate as much as others, we made sure to always send out data through email and keep everyone in the loop with the next meeting time. 

The skills learned from this exercise are directly applicable to the real world. It was intriguing  to see how the terrain surveying process works, even though we did it on such a small scale. 

Conclusion

In conclusion, this exercise forced our group to be extremely methodical and precise with each stage of the process. If I could have changed one thing about our process, I would have had us collect the elevation data in the XYZ columns to begin with. The large table was nice during the collection process, but we had to convert it to columns in the end anyway.