Surveying of point features using Dual Frequency GPS

Field Activity #9

Introduction-

    This weeks lab taught how to engage in a survey of various point features on campus using a high precision GPS unit. Features will be selected based off of codes that are already created for this project. The collection of these points allows of maps to be created for the study area on lower campus.

Study Area-

    The study area that was being focused on was the lower portion of campus for University Wisconsin- Eau Claire. Click here to see the study area of the lower campus portion. One thing to note of is that sometimes GPS units can be thrown off when standing under trees when they are full of leaves. Since this field activity is being conducted in early spring, there won't be an issue with collecting the points and possibly have even a higher accuracy then if this was conducted in the middle of summer.

Methods/ Results-

    With the class being broken into teams, each team would collect points outside on campus of either light poles, trees, garbage cans, or bike racks. The dual frequency GPS unit used to collect these points was called the Topcon HiPer (figure 1).

Fig 1. the Topcon HiPer located on top of the pole and the Tesla which is attached at the middle/ handheld.

The Tesla is the handheld device used to store the points collected in this field activity. One major key to note is making sure that the devices were as level as possible, mainly the HiPer. Without the HiPer being level, it would cause for the data to be skewed. When the data was ready to be collected, the Tesla was activated  to collect the GPS point wirelessly from the HiPer through Bluetooth. While the HiPer was collecting, it would give a reading of horizontal and vertical distance of how much it was off. The Tesla would continue to record 20 points in the same location as the horizontal and vertical distance continued to shift (figure 2). It would then take the average and give the reading of the point.

Fig. 2 Rachel collecting a light pole point. She is waiting for the 20 points to average out so she can save the point.

After completing the collection process of the various points, the data was then exported as points in a '.txt' file (figure 3).

Fig. 3 is the location of all the points recorded from the class.

This file would give X and Y coordinates allowing it to be used with the import XY tool to bring the points into ArcMap. After the point coordinates were brought in, an interpolation tool was used allowing the points to show the different elevations of the lower campus portion. The interpolation tool that was used was the triangulated irregular network or TIN (figure 4).

Fig. 4 is of the TIN showing the different elevation of the points we gathered, mostly of the parking lot.

 Looking closer at figure four, some interesting features are shown. There is a high spot relatively in the middle of the parking lot, assuming this is for drainage purposes. The high point is only a meter above the low point run offs, but that is all that is needed to keep the water flowing. There is also a high spot in the northwest corner of the study area. Here was an elevation increase from the sidewalk and landscaping made to this area. This area allows for drainage then to run along the base of it to different lower areas. Figure 5 compared to figure 4, shows just the points collected in the parking lot area of Davies. This gives a relative reference to show why certain areas have higher elevation than others.

Fig. 5 giving locations of the points in the Davies parking lot.

Conclusion-
    After completing this field activity there were a few things that were learned. Using the Topcon HiPer and Tesla is a good way of recording points if one has a wifi connection. Without that connection there would be a problem with trying to save the points of the location. This device is used to get very accurate data.