Distance Azimuth Assignment

Introduction

GPS technology has improved a significant amount throughout the years. At this point, it would not be ideal to leave your GPS technology at home when conducting a survey. However, there are situations where GPS technology and equipment will not be available and a knowledge of manual survey techniques is very important to have. Surveying with a grid based coordinate system will but in many cases, it will not be the ideal survey method. In this lab, a basic survey technique with distance and azimuth was used to map out the locations of trees in Putnam park at the UW-Eau Claire campus. 

Study Area

The study area of this project was Putnam park in the UW-Eau Claire campus. The surveying took place on Putnam Trail located behind the Davies Student center. This was an ideal location to survey different tree locations because of its interesting geographical location. One side of the trail is located in a flood plain that turns into a swampy land in the spring. The other side of the trail is part of the famous hill on the Eau Claire campus. Figure 1 is a map of the study area and where the surveying took place on the campus. 

Figure 1. This is a map that shows the study area of a
survey of tree locations in Putnam park. The study area
is shown by the green box. 

Methods

The class divided into three different groups. Each group had their own origin location where the distance and azimuth was calculated from. Varying forms of technology were given to each group. Some of the equipment that was used was a basic GPS unit to find our origin point, a tape measure to measure out the diameter of the trees that were mapped, a tape measure or a rangefinder to map the distance each tree was from the origin point, and a compass that could calculate the azimuth by looking through it. All of the data was recorded into a notebook to ensure that it could be kept and entered into a spreadsheet later. 

The methods to collecting the data were relatively straight forward. One or two team members would be standing at the origin point in order to collect the initial latitude and longitude of the point. Those team members would also measure the distance each tree was from the origin point as well as collect the azimuth angle. One or two other team members would be located at the tree that was being surveyed. These team members would identify the tree species as well as measure the DBH (diameter at breast height) of the surveyed tree. The remaining team members would be standing by to record the surveyed data. Team members rotated duties so that everybody was able to get experience with each responsibility. Once the required ten trees were surveyed, the group shared the collected data so that everyone had their own hard copy. 

Once all of the groups had completed the survey, all of the data was collaborated into a single spreadsheet. The collaborated data was imported into ArcMap so that the survey could be represented with a map. The Bearing Distance to Line tool in ArcMap used the table that was created to map out the azimuth and distance in a vector format. A line stemmed out from the origin and pointed to each surveyed tree. The next step was to use the Feature Vertices to Points tool to show the origin point along with each of the surveyed trees. 

Results

The original results of this survey were not ideal. Figure 2 shows the original mapping of our points. As you are able to see, the points are not all located inside of the study area. One set of surveyed trees shows up miles south of the study area. It is hard to tell at this point if the reason for error is human error or technological error. There is potential for error in both. It is very easy to incorrectly record the collected data into the spreadsheet. It is also very possible that the GPS was giving an inaccurate location. Regardless There were two sources of error in our original data. One of the sources I am very confident that it was human error and one of our origin points had two numbers mixed up in the X value. Because the study area is such a small scale, minor errors like that can throw off the data to a large degree. 

Figure 2. This map shows the error in the original survey data.
Luckily the errors were easily fixed and the final data is
much more accurate. 

The final map created includes the fix to the large error as well as a smaller error that offset an origin point less than 100 meters. Luckily the errors that were found in the data were easily fixed. Figure 3 shows the spreadsheet of data that was collected out int the field. Figure 4 shows the final map of the study area and the surveyed trees in the study area. The trees are represented by green triangles and the distance and azimuth data is shown by the orange lines. 

Figure 3. This is the final spreadsheet of data that was collected
in the survey. 

Figure 4. This is the final map of the survey showing the azimuths from the origin points
and the surrounding trees that were surveyed.

Conclusion

It was interesting to learn about azimuths and how we can use them to create maps when we are without technology in the field. For the most part, I think that the data that was collected was pretty accurate. I do believe that the errors that were encountered were due to the data entering process. Fortunately, we only were using three origin points. This made it easy to find where the errors were coming from. I think that this lab helped me to learn about other ways to collect data when technology isn't available for use. This is very important in this field because technology is great, but we can not rely on it. If you rely on technology and it fails, you are going to want to be able to work around that.