Field Activity #3: Conducting a Distance Azimuth Survey

Introduction:

For this experiment, a survey was conducted using the concept behind distance and azimuth. Although this is a basic survey technique, it works in many different situations. In this instance, we used sampling techniques to map point features on the University of Wisconsin Eau Claire campus, specifically trees around Phillips Hall Science Building. With today’s technology and the ability to acquire very precise location data, it is important to understand the basic techniques and tools used in field methods in order to function effectively and independent from advanced technology, such as drones.

For this exercise, a TruPulse laser distance finder was used to record the distance and azimuth readings for the data points we chose. We also used a compass that allowed us to record separate distance and azimuth readings. Although as a class we did not use the compass data, it is important to make comparisons of different technologies. We also used a distance finder or tape measure to measure the distance from our first station to the point feature (trees).

The TruPulse 360B Laser Rangefinder that was used to record our final distance and the azimuth readings for our chosen features (above-right). We also used a compass to compare azimuth readings between the two technologies.

My team and I chose to survey trees within the courtyard and surrounding Phillip Science Hall of UW-Eau Claire. Before conducting our survey, we were advised to take not of the concept of magnetic declination and how it differs from magnetic north. This refers to the magnetic pull on the compass due to earth’s magnetic field at our location on the planet, rather than what is known as “true North.” Below is a link to a video that was shown to the class for more information on magnetic declination:

Luckily, Eau Claire, WI has a small declination value of 2, so we know it would not impact our data collection. We then calculated the point features without using any coordinates, however, we will assign our starting point with GPS coordinates so that the data is usable in GIS systems.

Methods:

October 2, 2019

Cloudy, Rainy, ~ 15 degrees Celsius

Our first survey area was located within the courtyard of Philips hall, facing south towards Putnam Park trail. Once we decided our station area, we took the coordinates of that area, and began surveying from that point. We set up the TruPulse and began by taking readings of trees from right to left. Due to the bad weather that had rolled in that afternoon, our only option was to take points from the exit doors on the northeast side of the courtyard and take our survey from there. There were also heavy winds that would cause the TruPulse to shake, not allowing us to receive valid distance or azimuth readings.

This made collecting data extremely difficult, and due to time constrains, we couldn’t collect as many points as we could have. During this survey, we gathered three features. Our second survey station area was located south of the Phillips building near the bike racks and west of the large sculpture. After collecting data from this area, we had gathered a total of six point features.

After returning to the classroom, we transferred our data into an excel spreadsheet document for later use in ArcMap. Our data is shown below:

Table showing our data collected. For each point, we collected the azimuth, the distance from the station, attribute information of the trees, and the elevation of the tree.

Next, the excel file was imported into the geodatabase where we then used the “Bearing Distance Line tool to convert its information into a line feature class. 

We then converted our data to the points, using the "Feature Vertices to Points" tool.

The results of the tool and our data is shown below.

Results:

Discussion:

When looking at our map and data, it doesn’t seem like there is any input error, but that the readings from the TruPulse were off, causing our data to shift. It seems that even the smallest amount of error when calculating the azimuth will impact the resulting points. It is also possible that errors occurred when measuring subsequent readings of distance (meters) of the prominent features, especially considering the weather conditions throughout the course of this survey.

In the map above, the laser’s accuracy seems to decline as the object is farther and farther away from their actual locations. This error comes from the TruPulse’s decreasing accuracy with distance, as well as the users’ error as distance increases.

Conclusion:

Although we did use an expensive tool in gathering our data during this survey, using higher quality equipment doesn’t always mean that there will be no error. Utilizing simpler equipment may have been easier. Overall, the purpose of this experiment was to familiarize ourselves with using tools in calculating spatial relations without a coordinate system. These methods are useful in areas where there is no access to advanced global positioning and in situations of technological failure.