Lab 4: Conducting a Distance Azimuth Survey

Introduction

For this week’s lab, we were tasked with mapping out point data using a variety of survey methods. While the equipment and technology used to record the distance and azimuth of each point varied, the result was in the same format to allow us to import the coordinates and values into ArcMap to map out the point data. For our survey, we chose to map trees, benches, light posts, and fire hydrants within a quarter hectare plot located in the southwest corner of Randall Park located on the 300 block on Niagara Street in Eau Claire, WI using a tripod mounted laser device that could simultaneously display distance and azimuth.

Methods

Before we went out to survey our AOI, Randall Park, we first had to become familiar with the equipment and different methods available to us. At our disposal was a compass, sonar range finder, laser device, and measuring tape. First, we learned the basics of how to determine a point features azimuth using a compass by simply holding it up to one eye and pointing it toward the object you were surveying to see the azimuth displayed within. When using a passive survey technique such as using a compass to record azimuth, magnetic declination from true north must be accounted for. Magnetic declination naturally fluctuates, but is also based on geographic location. Using this website, http://magnetic-declination.com, to view a specific locations magnetic declination, you can derive the adjusting value needed to correct your compass. Fortunately for Eau Claire, this adjusting value is so small and essentially insignificant; no adjustment to our equipment was needed for this survey.

 Next we moved on to learn how to record the distance each point was from the survey station. To do this we had two methods to use. Aside from using measuring tape to measure bearing distance, we decided to use a bit more high tech approach by using a sonar range finder. The device had two parts, a transmitter, and receiver and works by sending the transmitter down range to send a sonar pulse back to the receiver which then displays the distance between the two systems parts on the receiver. Next to stream line this process we learned how to use a laser device that could measure each component and display bearing distance and azimuth simultaneously to streamline data collection. For our survey we decide to use the laser device to expedite data collection. The device itself is highly accurate, but instead of just holding onto it when recording the point data, we decided to mount it on a tripod so every point we surveyed had the exact same coordinate of origin to maintain data integrity and accuracy.

Conclusion

            I found this lab very helpful in understand how to survey using the bearing distance and azimuth method. It showed how multiple different techniques with varying levels of technology can achieve the same result. Although our data appears to be seamless and complete when displayed on its own, when projected on top of a base-map, there are a few problems. One problem is that we “ball parked” the coordinate of origin that signified the location of our survey station by locating it on an aerial instead of using a GPS to record the exact location. Another issue we ran into was that we did not have a uniform point on the trees where the distance reading was taken. Since we were in a park with lots of things obstructing each tree, we had to rely on an unobstructed line of sight to each point feature so sometimes the distance was measured from the base of a tree, and sometimes it was measured a few feet up the trunk of the tree. Although distance data was not greatly influenced by this, it still affected accuracy. All in all, this lab demonstrated multiple different survey techniques very well, and proved very helpful in understanding how to map point features using the bearing distance and azimuth method.  

Shown here is Brandon Surveying the quarter hectare plot using the tripod mounted laser device.

Above is an image looking north east into Randall Park showing the trees and other point features surveyed.

As Brandon surveyed the AOI, he repeated the bearing distance and azimuth values displayed on the screen, and I recorded the data to later be entered into an excel spreadsheet.

To establish a quarter hectare plot, we first measured out 50 meters east and 50 meters north from the origin of our survey in the southwest corner of Randall Park.

Shown above is the tripod mounted laser device used to survey Randall Park.

Shown above looking west down Niagara street is one of the markers we used to signify the 50 meter mark away from the origin of our survey to use a reference to show the boundary of the quarter hectare plot.

The map above is the result of our survey of Randall Park using bearing distance and azimuth to record point feature data. We were only able to record 20 features within the quarter hectare plot so we continued in a radial manner to shoot and record other trees from the western edge of the plot all the way around to the southern edge.