Creating a Digital Elevation Surface

Introduction:

        Technology often fails-- this was an underlying theme presented to us in our first assignment of geog336. In times where technology fails, it is crucial to have the ability to think critically to overcome our reliance on the plethora of gadgets making up our field research arsenal.  Simply put, the most important skill to acquire through higher education is the ability to think critically.

Methods:

  In our first assignment, we were to use improvised survey techniques to create an elevation model in the form of a sand table. Our study area for this assignment was a gardening box measuring roughly 8 x 4 feet.
We began our survey by creating various terrain features such as hills, valleys, depressions, streams, etc.. Sea level was initially defined as being level with the top surface of the 2 x 8's creating the gardening box.  To simplify the process of importing the data into ArcGIS we kept all values positive and chose to change what was considered sea level.
        To record the elevation data we needed to create a method of identifying where each feature was located.  We designed a grid coordinate system with x,y, and z values with cells being 6 x 6 in. Each cell was recorded in relation to the origin on the northeast corner of the box. Once the layout was created we used a tape measure to find and record our elevation data. Measurements were taken from where the ruler touched the terrain surface to where it intersected with our grid.  After our data was recorded we went to the computer lab and entered it into a spread sheet to be imported into a GIS.

 Beatriz and Nick measuring our grid 

Discussion:

Having the opportunity to conduct field work in our discipline is very important.  It helps you to realize that things don't always work out as they do on pen and paper.  This emphasizes the importance of being able to think critically in overcoming any dilemmas you encounter.   Going into the project I had an elaborate idea of how I wanted to conduct the survey; however, it didn't turn out exactly as planned.  Instead of using nails to anchor the string for our cells, I figured tape would work fine.  I didn't take into consideration the below zero temperatures would make it difficult for the adhesive to bond.
A concern of mine related to the data gathering process is the amount of error that will likely have occurred.  If elevation values weren't recorded exactly in the center of our cells our results could be thrown off. Also, our cells measuring 6 x 6 inches doesn't allow for very precise data, especially considering we only recorded one elevation per cell. Two ways to alleviate this problem would be to either make smaller cells or to measure in multiple areas in each cell and calculate the mean.  The GIS software has the ability to interpolate new data points; however, you need to provide a large enough sample for it to work well.  During the second phase of this project, it is likely that our data set will have to be altered in a way to make it resemble interval data. As is our data is somewhat confusing since larger numbers actually represent areas of lower elevation.

Above is our data sample. Note: the larger the number the lower the elevation this may present a problem. 

Conclusion:

        This assignment provided a great opportunity to think critically when given the bare minimum of instructions. How we completed the project was left entirely up to us and there were no linear paths to follow. Many classes provide all the instructions from start to finish and, more often than not, the skills you learn are difficult to retain. In the second part of this assignment, we will be Importing our data to see how it spatially turns out. During this process it will be much more clear whether or not our methods were successful.