Assignment #1: Creation of Digital Elevation Surface using critical thinking skills and improvised survey techniques

Introduction

The goal of this project was to familiarize ourselves with the method of creating a landscape terrain map. We were instructed to build a small-scale landscape with a number of physical features and then develop a system for taking elevation points on the plot and implement the system to record the elevation data.

Methods

First we had to build the terrain up from scratch.  A garden planter box was to be our study area.  We chose to have the top of the planter act as our baseline.  The box had dirt at the bottom and snow filling it.  We leveled off the snow to our baseline and then sculpted our landscape features.  We were required to have a hill, a ridge, a plain, a depression, and a valley.  From one end of the box to the other are our hill, plain, a rather large mountain with a depression at its top, our valley and finally our ridge.  We are pleased with our efforts.

Our finished landscape.  Note our hill in the bottom left, our plain in the bottom right, our mountain with depression in the center, our valley beyond it, and our ridge feature near the top.

Next we had to devise our method for surveying the landscape.  We decided to make a grid on the surface with 5 centimeter increments.  We marked the grid lines on the edge of the planter in marker.   The plot’s dimensions are 110 cm by 235 cm, so we had 22 marks width-wise and 47 marks lengthwise, each mark spaced five centimeters apart, equaling 1,034 grid points.  The bottom right corner of the box plot was the origin point with x,y coordinates of 0,0.  X values went from 0 on the right to 110 on the left.  Y values went from 0 on the bottom to 235 on the top.  When this was completed, we were faced with the somewhat daunting task of taking the measurements for each of those points.

We began by laying a string across the surface of the landscape at each lengthwise grid line, from 0 cm at the bottom (where the hill is) to 235 cm (the end with the ridge).  This marked a line on the snow surface.  We then began our first method of taking the measurements, which was to hold a meter stick vertically over each grid point and press down into the snow until the stick reached the hard-packed baseline, and then read the depth off of the meter stick.  The data was recorded as x,y,z points, where x and y describe the two dimensional grid point and z describes the height.  

Here we are using our first method for measuring the elevation of our grid points.  This method only employed two team members at a time.  Jeremy, seen in this picture, took the measurement and read it off, while another team member recorded it.

We employed this method to measure the elevation of the hill and plain.  This method would not have been effective for measuring the mountain, so we adopted a new method. This new method involved two meter sticks.  One was held vertically on the edge of the planter at each lengthwise grid line, while the second was held horizontally and extended out to the width-wise grid point.  The elevation of the horizontal meter stick in relation to the vertical meter stick was recorded.  

Here we are using our second method.  This method was much more efficient, and required the use of more of our team members.  Shown here, from left to right, are Blake, recording the data directly into Excel, Cody, holding the vertical meter stick steady, Jeremy, positioning the horizontal meter stick, and Zach, reading and calling out the measurement for Blake.

This method was better in two ways.  It was more precise, as we were not estimating the depth of our baseline with every measurement as we had with the first method, and it was also quicker, as we were able to simply slide the horizontal meter stick along to each new point.

Discussion and Results

The day that we did this work, it was 10 degrees outside and there was a decent freezing wind to contend with.  As a result, we needed to take several breaks from the measuring process to go inside and warm up.  This increased the amount of time that this process took. 

The skills used in this exercise are applicable for use in a real life situation, albeit on a much larger scale and with more accurate tools for measurement.  The use of a grid ensures that points are taken everywhere on the plot and at equal distances, which will help out with the mapping.