Assignment 11- Topographic Survey

Introduction

In assignment 11, the class went outside to use a high precision GPS unit.  20 points were taken and each student was able to collect a point using the GPS unit.  The 20 points were then used with different interpolation methods which produced image displaying elevation of the study area.

Study Area

Below in Figure 1 is the study area outlined in red for this project.  It is a grassy area on the UWEC lower campus in between the buildings.  The points were collected on November 30, 2016.  The temperature was in the mid-30's with light rain.

Figure 1: The study area for this assignment.

Methods

The class went outside to the grassy knoll on the UWEC campus where Dr. Hupy proceeded to explain how to use the GPS.  The GPS is pictured in Figure 2 being used by Heather and Sarah.   By using the random sampling method, groups of two would take a point together for a total of 20.  More points would have been taken, but technical issues only allowed 20.  After everyone received a turn to collect a point and 20 were taken, everyone headed back inside.  The points were then uploaded to a text file for the class.  From there everyone was on their own.  The points were imported into an excel file in order for it to be used in ArcMap.  It was discovered later that the points are in the wrong UTM zone.  Here in Wisconsin is in zone 15, but the points were taken in zone 16.  This produced some differences within the data, however the point still gets across what the data is supposed to look like.  The excel file was imported into ArcMap and then converted into a point feature class.  From there, five interpolation methods were used on the points.  These produced different results.  These interpolation methods were used in a previous lab in which the methods are described.  

Figure 2: Heather and Sarah using the GPS to collect a point.

Results

Below in Figures 3-7 are the images produced using the five interpolation methods.  These results are not 100% accurate because of the zone mix up.  All of these methods created different results which depict the study area in different ways.

Figure 3: IDW interpolation of the study area.

Figure 4: Kriging interpolation of the study area.

Figure 5: Nearest neighbor interpolation of the study area.

Figure 6: Spline interpolation of the study area.

Figure 7: TIN image of the study area.

Conclusion

Ultimately, none of these methods produced a highly accurate representation of the study area.  This is because of the minimal points taken within the study are.  However, nearest neighbor and TIN did a decent job of representing the area.  If more data points were taken these interpolation methods would have produced more accurate results.  The GPS that was used was also so precise that it would have been very accurate in representing the area.  It was a good introduction to using this type of GPS and looking at it's results.