Distance Azimuth Survey

Introduction:

While it is important to have an understanding of the latest technology when conducting field research, it is just as important to understand how to conduct research the "old fashioned way" when technology fails. This was the central theme of this exercise i which the students conducted a Distance Azimuth survey of trees in Putnam Park on the University of Wisconsin- Eau Claire campus. This survey technique is basic but effective, using a range finder and compass to calculate distance and azimuth (measured in degrees between 0-360) respectively students were broken up in groups of three or four to collect the data, which was then uploaded into Arcmap for further processing.

Study Area:

Figure 1
Study Area Map 

The data for this exercise was collected in a small section of Putnam park on the UW-Eau Claire campus near the Davies student center and the Phillips Science Hall. The area is primarily low in elevation as can seen in its swampy terrain. On the other side of the wetland is a walking trail and a large ridge with a stairway leading to upper campus. The study area included a variety of deciduous trees such as birch, basswood, oak and maple. 

Figure 2
Study Area site with swamp (left of image) and ridge (right of image) 

Methods: 

Using a variety of tools, the distance and Azimuth to each tree was collected from a central point and recorded in a field notebook. The data was then entered into an Excel spreadsheet to be uploaded into ArcMap.

To begin, the GPS coordinates were collected for the survey point using a Garmin Etrex GPS device. This step is important because it is necessary to have an accurate point of reference for a survey.

Figure 3
Garmin etrex Device

Once the reference point coordinates were collected, the distance and azimuth was measured from this point to ten nearby trees. This was done using a laser distance finder device. One group member stood on the reference point to take the measurements and then reported them to the other members who recorded them in a field notebook.  The device is easy to use, simply requiring the user to switch to the setting for what they wish to measure (in this case distance and azimuth) and point a laser at the target to obtain a reading.

Figure 4
Example of Distance Finding Device

Unfortunately, one device had some technical issues and was giving inaccurate azimuth readings. As a result, an survey compass needed to be used. Unlike a traditional compass, an survey compass has a small viewfinder the user looks through which shows the azimuth the compass is pointed in.

Figure 5
Example of a Survey grade Compass

The tree diameter was also recorded as well as the tree type. This information is important because it may be used to make observations regarding tree size in relation to its location.

Once the data was collected, it was entered into an Excel spreadsheet with each field getting placed in its own column and uploaded into a geodatabase on ArcMap. Once uploaded the Bearing Distance to Line tool was used to show where the trees were located in reference to the survey point. A tool was then used to convert the vertices of the lines to points so the trees themselves could be symbolized.

Results:

Figure 6
Map of Tree location and Azimuth from the central measurement point.

Once the data was processed in ArcMap, the trees locations could be mapped by converting the vertices of the azimuth lines to points.