Lab: Field Survey 2 - Distance Azimuth Survey and Field Navigation

Introduction/Background

Lab 2 was designed to put the students the mindset/perspective of a total station that is typically used in the field. Rather than using a total station’s ability to compute the necessary information, we put ourselves in the lens of a device called the TruPulse Rangefinder and recorded the data manually. Using this method, we can understand how the data is collected calculated digitally by more complex and higher end technology we will most likely be using in the near future.

Data Collection Procedures and Techniques

The process in which was created for this lab

Azimuth (AZ)

The azimuth is a method of angular measurement based on a 360-degree circle. It follows a ‘clockwise’ pattern starting at North (0) continuing to East (90) to South (180) West (270) and so on. The increment at which the object is compared to the measurement instrument determines the azimuth.

Survey Bearings

Your survey bearings are your angle of perspective based on the 360-degree circle, as well as cardinal direction. With north and south as the baselines of angular measurement, survey bearings are easy to figure out. (Figure 1)

Figure 1. Survey Bearing Diagram

Horizontal Distance (HD)

To create a 2D map, we need to calculate the HD, or horizontal distance between the instrument and the object. We use horizontal distance, because if we use slope distance, we would have our points plotted in the incorrect spot.

TruPulse Rangefinder

This is a tool used by surveyors to establish shots and acquire the AZ and HD values shown through the viewfinder for each shot. By using this device, we can find measurements for various shots at each control point to create a web of coordinates. (Figure 2)

Figure 2. TruPulse Rangefinder

Total Station

A total station calculates the difference in height from one point to another using trigonometry.

Data Collection… The Numbers

We recorded HD and AZ measurements from each pre-established control point location.

Each of the control points came with given values (Northing_y, Easting_x, and Elevation) to which we will base our further measurements upon. In each dataset, the Northing_y, Easting_x, and Elev values are constant. This is because we are recording the perspective from our location and cardinality starting from the same origin, just viewed in different angles.

Our HD was the distance in meters (dist_m), and the AZ was the degree in which we were facing. The distance is converted to feet to keep data consistent with our designated PCS. A short description is recorded to use as a reference when completing more complex geoprocessing tasks.

Control Point 101 Table (Figure 3)

Figure 3. Table containing various measurements collected from control point 101.

Point 101 is in the green space of the University of Wisconsin-Eau Claire’s campus mall. The representation for the data is symbolized by the magenta ducks and star icons. (Figure 11 results map)

Control Point 101 Map (Figure 4)

Figure 4. Map showing the points collected from the 101 control point.

Control Point 102 Table (Figure 5)

Point 102 is located on the Eastern Bridge on the map, denoted by the blue duck and star symbols.

Figure 5. Table containing various measurements collected from control point 102.

Control Point 102 Map (Figure 6)

Figure 6. Map showing the points collected from the 102 control point.

Control Point 103 Table (Figure 7)

Point 103 is located on the Western bridge of the campus mall. The data is represented by yellow ducks and a star.

Figure 7. Table containing various measurements collected from control point 103.

Control Point 103 Map (Figure 8)

Figure 8. Map showing the points collected from the 103 control point.

Data Processing Procedures and Techniques

ArcMap tools used in Field Survey 2 Lab

Once our data was recorded in Excel or as a text file, we were then able to import the xy data into ArcMap for further analysis and mapping. Assigning Eau Claire specific coordinates to the xy data is key because the control points from which we based our measurements on was recorded in the Eau Claire County coordinate system. If it were not to be using the same coordinate system, it wouldn’t appear where it was intended. In our case, we used the NAD 1983 (2011) WISCRS Eau Claire (US Feet) projected coordinate system.

After importing the XYZ points, we had to change the “events” layer into something more reasonable. The control points should be exported as a shapefile.

To turn the XYZ data from each control point, the bearing distance (distance in feet and bearing in azimuthal degrees in our data) must be transformed into lines. To do that, we use the Bearing Distance to Line data management tool. (Figure 9)

Figure 9. The input for the Bearing Distance to Line tool is the control point and its xyz data, the output is the line generated following computation’s location, the x/y fields are to indicate what we saved the x/y data under, as well as our distance field/units, and bearing field/units. The spatial reference system must be identical to the county system.

Once the bearings have generated a line, we must now turn the end vertices of each line into the specified target or shot location. This is done with the Feature Vertices to Points tool. (Figure 10)

Figure 11. The input for the Feature Vertices to Points tool is the line that was just created from the Bearing Distance to Line tool, the output will be the vertices’ location in the drive, and the point end that is intended to come from this tool is endpoints.

Modeling Results in ArcMap

Completed Distance Azimuth Survey and Field Navigation Map with all control points and shots. (Figure 12)

Figure 12. This map shows the compilation of all three control points and their respective points collected in a finalized map.

Shortcomings

We relied on our manual data collection skills rather than a fully functional total station. Unfortunately, some of our plotted points did not end up where they were intended. An example would be the yellow ‘duck’ that somehow waddled into the Davies center from control point 103. The result of human error is a factor that should be taken into consideration whenever data is measured and recorded by people.

Conclusion

Although not all our points turned out to be accurate, we were able to turn ourselves into manual total stations and turn that data into a comprehensible map. Further use of these skills will be important in future data collection endeavors and comprehension.

Bibliography

Klang, J. "Azimuth & Distance Survey." Lab Report. 2015.

Bergervoet, Michael. Powerpoint with detailed lab instructions provided for completion of lab exercise. 2018