Surveying Point Features using Dual Frequency GPS

Introduction

Each of us in groups of two went out on campus and surveyed various objects with a high precision GPS unit. My partner and I surveyed one tree, one fire hydrant and the five light poles in the parking lot behind the Phillips building. This survey was much different than the distance/azimuth survey taken last week, while that showed the general location of trees, these maps show highly precise locations of certain features. 

Study Area

This study took place in Eau Claire, Wisconsin on the UW-Eau Claire campus in the area behind the Davies building and Phillips building. 

Methods

Groups of two went out behind Phillips in the parking lot to survey objects, each group of two took turns going outside surveying 4-5 features. With my partner, we were the sixth group to head out and take the survey. We simply went out on campus in the parking lot to meet our professor Joe Hupy, who then taught us how to work with and record points on the GPS. My partner and I recorded one tree, one fire hydrant and five light poles. With the tree we recorded one attribute and that was the diameter of the tree. This data was later unable to transfer so it is not mapped below. This GPS would take 20-30 points and then take the average of those points for the location. It would do this process fairly quickly and then record and save the data.



Figure 1: The entire GPS unit

Figure 2: Screen of the GPS while recording the location of an object. 

Results

Below are the maps created from this GPS survey. It shows the various objects we recorded including fire hydrants, garbage cans, light poles, mailboxes, signs, telephones, and trees. Added was a topographic map of campus and each feature is exactly where it is supposed to be. If you were to compare these maps to the maps of last week, there are some major differences. In the distance/azimuth maps the trees appear to be in the Phillips building but using this high tech GPS it places the features where there are in the real world.

Figure 3: Map showing features recorded, color coded.

Figure 4: Unique symbols map of the objects recorded

Conclusion

It depends on what you're surveying but if the technology is available and its working opt to use it. Although distance/azimuth surveys are excellent to use if wondering about the general location of objects,  the high precision GPS worked for this survey method because we wanted to know the precise location of these objects and to learn another way to take a survey.