Conducting a Distance/Azimuth Survey
Introduction
Technology can fail. While it may be hard to believe, the technology we lean on so heavily has to potential to stop working, be inaccessible, or be too infuriating to understand. As geographers, it is easy to forget that many of the complex things we can do now for surveying and navigation were once done by measuring and using a compass. Presently, we have a plethora of technology at our fingertips that can quickly solve our problems. However, we must be ready to conduct field work without the use of a Juno or eTrex. This goal of this exercise was to better learn how to manage if technology is unavailable to us.
In order to properly conduct a distance/azimuth survey, one needs to pieces of equipment: a compass and a measuring device (tape measure, measuring wheel, etc.). The compass allows us to find the azimuth. Azimuth is described as the distance of something in relation to a 360° compass (NOAA). This can tell us the direction (0-360°) of an object in relation to our position. The measuring unit can then tell us how far away the object we are curious about is. If we know our latitude and longitude we can determine where something was on a map in relation to our position. For this exercise (ironically), we utilized a TruPulse Laser system to determine our distance and azimuth, however the procedure was the same if we had had a compass and measuring device. Using the TruPulse we were able to acquire the azimuth of an object to us and the horizontal distance of an object to us. My partner, Michael Bomber, and I chose to acquire car color and make. This survey was conducted in the parking lot behind Phillips Hall and the Davies Student Center on the University of Wisconsin Campus on April 2 at 12:30 (Figure 1). After acquiring the data, we brought the data into ArcMap for processing.
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| Figure 1. Map showing the study area that the exercise was conducted in. |
Method
Before heading into the field we created a geodatabase for our data to be put into when we returned from the field. In the field we positioned ourselves at two different locations. The first was off of the southeast corner of Phillips Hall (Figure 2). We took sixty-nine data points at this first location, recording the color and company of cars parked in the parking lot. We then moved to a vent off of the southeast corner of Davies Student Center (Figure 3). The survey was conducted by mounting the TruPulse laser rangefinder on a tripod to maintain a consistent location with this to collect our data from.
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| Figure 2. Panoramic photo of the first location data was collected from off of the southeast corner of Phillips Hall. Sixty-nine different data points were collected from this location. |
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| Figure 3. Panoramic photo of the second location data was collected from off of the southeast corner of the Davies Student Center. Thirty-one different data points were collected from this location. |
Once we returned from the field, the data was imported from Excel to ArcMap with an ObjectID field and Latitude/Longitude points for the proper points. Two different locations were used so there are two different coordinates of latitude and longitude. In ArcMap, the Bearing Distance to Line tool was used to create a series of lines based off of the starting XY coordinates, the distance field, and the azimuth (Figure 4 and Figure 5). The points collected are based off of the earth and not a projected coordinate system, so when using the tool the WGS 1984 coordinate system should be used.
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| Figure 4. The Bearing Distance to Line tool. The Excel table was the Input Table and the appropriate fields were designated from the Excel table. Bearing units were taken in Degrees, distance was taken in Meters, and the Spatial Reference was in GCS_WGS_1984. |
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| Figure 5. The study area and the result of the Bearing Distance to Line tool. The result was a series of lines originating for a common point and extending to a point based on the azimuth and distance recorded. The ends of these lines match up with the vehicles we collected data for. |
Next, the Feature Vertices to Point tool was used to create points where the end of the line was (Figure 6 and Figure 7). One thing to remember is to make sure to select the "End" under the Point Type, or the correct vertice may not be created.
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| Figure 6. The Feature Vertices to Point tool. Data from the Bearing Distance to Line tool was input and the end vertices were requested to plot. |
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| Figure 7. Result of the Feature Vertices to Point conversion. The red points are the resulting points from the end vertices. |
After the feature vertices to point tool was run the points were joined by ObjectID with the excel table to allow for color and company to be shown.
Results and Discussion
The resulting data can be expressed in a series of maps and graphs (Figures 8-12):
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| Figure 8. Graph showing the number of cars of various corresponding colors. Red, Silver, and Blue were the most common colors. |
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| Figure 9. Spatial distribution of the color of cars from where we collected them. |
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| Figure 10. Zoomed in view of the distribution of points we collected for color. |
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| Figure 11. Graph showing the number of cars of various corresponding companies. Toyota, Chevy, Ford, and Honda were by far the most common companies. |
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| Figure 12. Map showing the location of various company makes of vehicles. |
There were a few things we wanted to pay attention to when collecting our data that past courses came up against. We made sure that the object we were pointing the laser rangefinder at was not too small, too far away, or too moving. Other classes had issues with trying to collect points like this and they came up against some issues because of the difficulty of collecting points like this. We also had to make sure that the locations we used were findable on a current map of the area. The basemap we used was from 2013, so the new Davies Student Center was in place and the parking lot was mostly similar to what it is now. We were able to find the points we stood at with ease.
Conclusion
This exercise helped to teach us how to record points in the field by conducting a distance/azimuth survey instead of using a GPS device. This is a extremely helpful tool that can help us to conduct surveys if our technology was to fail or give out. Even though we used a laser rangefinder to conduct this survey we understand the method of how to conduct this survey and even used a compass a little to compare what the compass read versus what the laser rangefinder was telling us. The skills learned in this exercise help to develop a base with which to broaden our geospatial navigational skills in the remainder of this course.
References Cited
NOAA. (n.d.). Glossary - NOAA's National Weather Service. Retrieved April 5, 2015, from http://w1.weather.gov/glossary/index.php?letter=a
