Exercise 4-Azimuth

Introduction

For this exercise we practiced another form of surveying. While the original Cartesian coordinate system, and measuring methods we created may have been good for the area we first surveyed (the sandbox), it does not lend itself so easily to larger areas. For this project our group was given a few sets of tools and told to survey a larger, quarter-hectare plot, area where we should measure at least fifty points. As a group, myself and Zach Robison, we decided to team up with another pair, Zac Womeldorf and Hannah Bristol, to collect similar points, but to use two different methods of data collection.

Methods

The first step was to become acquainted with our options for survey tools. The first option was a laser device called a TruPulse 360 (Figure-1). The TruPulse emits an invisible infrared laser which measures the distance and azimuth to a point from where you are standing. The second option was to use a compass accompanied with a ComboPro distance finder (Figures 2,3). This way we could measure the azimuth with the compass, and the distance with the ComboPro.

Figure 1-TruPulse360 and example of reading for distance purposes.

Figure 2-ComboPro Distance finder.

Figure 3-Compass used in conjunction with ComboPro to determine azimuth.

Figure 4a-Photo of data collection.

Figure 4b-Data collection

Zach Robison and myself decided to use the compass and ComboPro to take a few points outside Phillips hall. This provided us with a small sample to ensure we were able to understand and fully grasp the uses of each device.

Once we mastered the technique, we teamed up with Zac Womeldorf and Hannah Bristol to survey points on Upper campus on the north side of Horan dormitory (Figure-4). We chose this location because it seemed to give a plethora of points to survey, as well as was about the right amount of area to fit our requirements. It also seemed to be fairly out in the open, so if need be, we could check out the area from aerial photographs or in satellite images. That way, we could also compare our final data with images of the area so see how accurate or inaccurate the methods of survey were.

FIGURE 4

We then used the distance finder and compass to measure out 32 individual points within this area. Unfortunately we were unable to take 50 points because of the interference of the first 32 points we took. Trees were often blocking other objects (trees, fence posts, signs etc.) so it made reading them with the distance finder impossible. For a full list of the points surveyed, see below (Figure-5).

Figure 5-Final Data collection in excel format, Ready for import into GIS

Upon returning we were able to convert the written points and survey data into an excel table (Figure-5). We then imported this into a created geodatabase, put the table into ArcMap, and ran a spatial tool called the Bearing Distance to Line tool to map the locations of our points. This took takes the origin and uses the azimuth and distance field to calculate what direction and distance the point is from the origin. (Figures 6-10)

One error that we ran into was our spatial reference was skewed when we brought the data in. Our original Latitude and Longitude readings were not precise enough, so our origin wasn’t exactly on our true spot of measuring. We corrected this in ArcMap by using the Identify tool on the basemap provided by Bing!© maps to determine our exact latitude and longitude. This corrected our origin issue, and thus displayed the points more accurately.

Our two groups cooperated together by sharing the data we collected. Since we collected largely the same points, we thought it would be interesting to see the difference in measurements between the two measuring systems. (Zac W. and Hannah B. used the TruPulse to measure their points). We shared our data with them, and they shared theirs with us (Figures 9a, 9b). We went through the same data import process as the first time, and then were able to compare what the differences were (Figure 8). As you can see, the data did differ quite a bit. In the discussion portion we will explore this fact more closely.

Figure 6-Adding the Table in excel to the geodatabase.

Figure 7a-Using the Bearing Distance to Line Tool.

Figure 7b- Using the Bearing Distance to Line Tool.

Figure 8-Data Collection points with no spatial reference. Displayed is both collection methods and the variances between them.

Figure 9a-Data Collected by Compass and ComboPro

Figure 9b- Data collected

Figure 10-Data Points from Both Collection methods overlaid on Bing! maps basemap.

Figure11-Final Compass survey

Figure 12-Final Laser Survey

Figure 13- Compass and Laser survey data

Discussion

As you can see from the provided map, both data collection methods came up with different data as the end result, even though they were mapping the same exactly points.  You can see the error in the fact that the lines do not overlap in all places, and they both terminate in different places. We attribute this to the fact that neither data collection method is going to be perfect. For instance, we were only mapping on a 2D plane, how would the TruPulse or ComboPro react to an elevation change? And would that elevation change even show up in ArcMap?

User error may also be another explanation for point variances. It was cold, snowy and windy, nobody operates perfectly in any conditions and these adverse conditions could easily lead to a misread azimuth or distance measurement.

One source that may create small amounts of error in our survey could be the declination between magnetic north and true north. However, this is unlikely because here in Eau Claire our declination adjustment is nullified by the fact that we sit almost exactly south of both magnetic north and true north. It did, undoubtedly play a very small role in error in our data collection, though very small.

Although neither method proved to be perfect, both had good advantages. Using the ComboPro and compass was a very simple and easy method. Not a lot of equipment could have broken or been malfunctioning while in the field. The compass always will work because it doesn’t need batteries. This is perfect for situations where you can’t always replace certain items in the field, short of losing it, a compass will always work for you.

However, in more recent times the compass has been replaced with more technologically advanced survey methods, just like the TruPulse. It also is easier to go into a GIS like Google Earth and measure out points with the Distance and Declination tools. A survey like that doesn’t even require you to leave your seat.

Conclusion

In the end we are left with a Map looking something like what you see in Figure 10. The tools and skills we gained from this exercise definitely helped us create a new skill-set for surveying and displaying a plot of land. I found the exercise to be a great learning experience and know it will prove to be helpful in the future. Plus learning two different methods for survey was helpful to have a backup plan if one system were to fail while working in the field.