Lab 11: GPS Topographic Survey

Introduction

The purpose of this lab was to gain experience in collecting data with a high precision GPS unit.  The study area was a grassy knoll located on the UW-Eau Claire campus. 

Methods

In this lab, data was collected using a Topcon HiPer high precision GPS unit with a Tesla field controller (see Figure 1).  Due to complications with the geography department's ArcGIS account, the class was only able to collect 20 elevation points total.  Points were collected by two students at a time in a random survey throughout the grassy knoll.  Each student took a turn operating the Topcon HiPer and the field controller.  After all of the data was collected, the instructor was imported as a text file for future use in ArcGIS. 

To better visualize the elevation of the knoll, a number of interpolation methods were used, namely TIN, Natural Neighbor, Spline, IDW, and Kriging interpolation. 

Figure 1: Picture showing class members operating the Topcon HiPer

Results & Discussion

The results of the interpolations all were different, with various advantages and disadvantages.  To read more about the pros and cons of each interpolation method, check out Lab 5: Visualizing Terrain Survey.  The spline interpolation appears to provide the best visualization of the actual terrain. 

One of the main sources of error in the interpolation maps was the fact that the data was entered in as if it was in UTM Zone 16, when it should have been Zone 15.  This caused some distortion.  After importing the data as a text file, some of the fields were also mislabeled, which caused some confusion.  Despite this, all of the interpolations were performed successfully. 

Figure 2: TIN interpolation

Figure 3: IDW interpolation

Figure 4: Kriging interpolation

Figure 5: Natural Neighbor interpolation

Figure 6: Spline interpolation

Conclusion

This lab provided a good introduction to using a high precision GPS unit.  Ideally, each student would have been able to collect more than just two points to gain more experience, but the class made do.  Additionally, the UTM zone fiasco proved that it is important to be very careful when setting everything up for data entry on the field controller.