Activity 7: Distance/Azimuth Survey

Introduction

This week the focus was turned on to learning how to conduct field work without the reliance on technology. Technology is generally very useful and helps speed up the process of performing field work, but it might not always be reliable or available. So it is important to learn new techniques for data gathering for if and when technology is not practical or when technology fails. Technology could fail due to a number of reasons, such as extreme weather conditions, a device freezing up, running out of batter, etc. Access to a given study area may only be permitted for a short period of time, so it is important to be aware of different survey techniques that could be used if technology were to fail. For this field activity,  two different types of rangefinders were used to map out various trees on campus. The first surveying method required two separate instruments to find the distance and the azimuth such as a rangefinder (figure 1) and a compass (figure 2). The second surveying method utilized an instrument that could measure both the distance and the azimuth (figure 3). 

figure 1: This image shows a Vector Optics laser rangefinder device that was used in the field to collect distance data. This device requires two users where one user holds a device at a desired location and the second user points the unit at the window of the device to determine the horizontal distance between the two devices. 

figure 2: Here is a Suunto compass which was used to find the azimuth by looking through the hole and pointing it at a desired object. 

figure 3: The TruPulse laser shown above was used to collect both the horizontal distance and the azimuth in the field. The user points the unit at a desired object through the eye piece and then fires a laser in order to acquire the corresponding data. This unit is handy because a user is allowed to find both the horizontal distance and the azimuth by using a single device. On top of that, the TruPulse can also be used to determine the height of an object as well as other pertinent information.

Methods

As a class we went near the side of Phillips, an academic building on campus, to conduct the survey using the two methods stated above. A corner of the sidewalk was designated as the point where each of us would stand to collect the distance and azimuth data for the two devices, which was recorded as the x,y location. The class had gathered distance and azimuth data for 17 trees in total along the Little Niagara creek near the side of the building. The tree species and DBH (Diameter at Breast Height) were also recorded. The data for each tree was compiled in a table in each of our notebooks during this field activity, to get accustomed to not using any technology. This data was then transferred into an excel spreadsheet (figure 4).

figure 4: Excel table of data gathered in the field.

Before we could transfer the data into excel, we had to convert our point of origin from degrees, minutes, seconds, into decimal degrees in order to properly and accurately represent the data on ArcMap. In order to do this, we divided the minutes by 60 to give us a precise decimal value. It was important to classify the X, Y and as well as the other fields as "numeric" in excel rather than just "general" so the values could be properly represented in ArcMap.

Once the excel file was imported to ArcMap, a tool "bearing distance to line" was used to display the distance and azimuth data from the table as lines on the map from the point of origin (figure 5).

figure 5: The end result from running the "bearing distance to line" tool on ArcMap.

The next step was to convert the data into points by using the "feature vertices to points" tool. This tool gives the end of the lines an endpoint which helps one to visualize the end of the line on the map (figure 6).

figure 6: The end product from running the "feature vertices to points" tool.

After the endpoints were added, a basemap could be used to show the accuracy of these surveying methods that did not require the use of technology (figure 7).

figure 7: The final result with the use of a basemap to show the accuracy of this method.

Discussion

This lab was very useful because it gave us base knowledge and understanding on ways to conduct field research if our technology were to fail. It was interesting to see how the horizontal distance was consistently different between the two units we had used and to see how accuracy is the limiting factor for the survey. A survey such as the one our class conducted does not need to be very accurate, however. A surveyor needs to mainly gather a liberal amount of data points that provide a general understanding of a study area. For instance, a tree on a survey map does not need to be in the exact location that tree is in the real world. The tree just needs to be in the general vicinity to allow for one to be able to interpret the study area. What is more important are the data and fields collected. The number of bird nests or the species of trees in the general location, for example, are more crucial than the exact location of those features. In order to avoid as discrepancies though, it is important for a user or multiple users to follow the same data collection techniques. It would not be in one's best interest if one user who is tall in stature were to hold a rangefinder right next to their chest and another shorter user were to hold a rangefinder lower to the ground and away from their chest. It is important to have uniform collection techniques in order to avoid as many discrepancies in the data as possible. Because the weather was not ideal, it is also important to take into consideration the way a user takes field notes. The use of a pencil is crucial to use in rainy or wet conditions. Pens tend to bleed and run when exposed to water. A small field notebook with waterproof paper would also be useful to have. To be aware of and make simple changes like those could save a lot of time and headache while working in the field. So as always, it is important to be well prepared for a task at hand before going out into the field. As a class we had mixed up our X and Y data so the data was not properly represented in ArcMap at first. So in order to continue, I needed to switch the X and Y values accordingly and also needed to add a negative sign to the X values based on the the longitude of Eau Claire.

Conclusion

This lab was very informative and helpful. Being able to use this new method of locating and plotting points will be extremely beneficial in the future when technology will let me down. I looked online at the rangefinders and noticed that they were quite expensive. So this method could also be applied to the use of a measuring tape and compass to find distance and azimuth of features. Being able to use TruPulse, Vector Optics, and Suunto are more tools I am now familiar with and the continued use of Excel and ArcMap are greatly helping me understand and be familiar with the two platforms.