Distance/Azimuth Survey

Introduction

For the distance/azimuth survey we learned how to make a map of the general location of trees using only distance and direction from hand held devices. The purpose of doing this was to learn about different ways of taking surveys and collecting geospatial information without the use of a GPS. Technical equipment fails all the time so learning a way that does not require this is very beneficial.

Study Area

This study took place in Eau Claire Wisconsin on the UW-Eau Claire campus. More specifically in the campus mall with our ground control point just north east of the Davies entrance and just north west of the Phillips building. Here trees were surveyed from the ground control point spanning out east. Tree attributes were collected from trees near the Phillips building on the south side of Little Niagra and on the North side of Little Niagra (this is the small stream that runs through the campus).

Methods

All students went outside Phillips to collect the tree species and tree diameter of all 17 trees collected. Materials used were:

• Sonic Electronic Measuring device
• Suunto Compass
• TruPulse 360 Laser

Figure 1: Sonic Electronic Measuring device

Figure 2: Suunto Compass

Figure 3: TruPulse 360 Laser

We took turns using the devices that measured the distance and direction from the anchor point. First we measured the distance from the ground control point to the first tree using the sonic electronic measuring device (Figure 1). This device has two parts the first part being the laser (on the left of figure 1) and the receiver (on the right of figure 1). One person holds the laser at the ground control point, another person holds the receiver at chest height in front of the tree. The laser "shoots" at the receiver allowing it to measure the distance from the laser shooter to the receiver. This number is recorded as the distance from the ground control point to the tree in meters. The next measurement recorded was the azimuth or the direction the tree was from the ground control point (recorded in degrees). For this, a student would hold the suunto compass (figure 2) up to their eye, keeping both eyes open. The azimuth was then recorded for the tree. The TruPulse 360 Laser (figure 3) was also used to measure distance and azimuth, this device can measure both at one time. It was used to double check the measurements of the other devices and to become familiar with multiple measuring devices.  Other attributes that were recorded for the tree were, tree species and tree diameter (Diameter at breast height in centimeters). These steps continued for the next 16 trees. Once all 17 trees were recorded with their specific attributes we recorded the GPS location of the ground control point which was 44.7975 degrees N and 91.5003 degrees W. This is very important for mapping the end results.

Once inside, the class collectively created an excel file with the trees and their according attributes. This was added to ArcMap by clicking File>Add Data>Add XY Data. This prompted a window where the table chosen was Direction_Azimuth3.xlsx> Sheet1$ with the X field being X (X coordinate) and the Y Field being Y (Y coordinate). The coordinate system remained Geographic Coordinate System because the ground control point was recorded in the GCS. This was added to the map where only one point was visible, this is our ground control point. To get the locations of the trees two tools had to be used. First the "Bearing Distance to Line" tool was used. This tool creates a new feature class based on line features constructed from the distance and azimuth field of our table. Once the values were entered for this tool, individual lines appeared to go out in the direction of the trees. The next tool that was used was the "Feature Vertices to Point" tool. This tool placed points at the end of each line, representing the trees we recorded. When entering point type for this tool it was important to change "All" to "End". If you used the default "All" two of every point would show up, which is not what we wanted. We only needed points for the end of each line.

Results

Figure 4: Location of Trees on Campus

Above is a map of the location of Trees recorded on campus (figure 4). It contains the ground control point, the trees recorded and the lines that represent the distance from the ground control point to the trees. It shows the general placement of the trees on campus. From the map it appears that the trees are growing in Phillips. This is not the case and the map looks this way because it is only showing the general area where these trees are located. If we were using a GPS for this particular project then we would be showing the exact location of the trees.

Figure 5: Trees labeled by species on campus

Some patterns I pick up from this is that the River Birch seems to only be located fairly close to Little Niagra. White birch are only growing on the South side of Little Niagra, but that may be because we didn't collect that many tree points.

Figure 6: Trees labeled by their diameter (cm)

Again if more points had been collected there may have been clearer patterns showing up here. With the 17 points displayed it does look like the smaller diameter trees are on the northern side of the map. This may be because these trees are located more in the campus mall which has been constructed fairly recently and had new trees added that obviously would have a small diameter. Trees with a larger diameter appear to be closer to Little Niagra and the Phillips building, possibly because not much change/construction has gone on in these areas and the trees have been able to grow for quite some time.

Conclusion 

Knowing and understanding different ways of gathering data is very important when working with geospatial information. GPS units are not always reliable to work or have a signal when out in the field. Knowing other methods such as the one we learned in this lab of recording a ground control point and then recording objects outward from that point by listing the distance and azimuth, is very important. 

Sources

• https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUxH3YyerLjhZ-C4jwVcTRIy2PmHfdItSSNTRxDUbz9elaqXhTe2D5cIjF8c7vKPkURrYVPOBZjKVU9h01zT3Pk_fMWStvbBufuKFOpFIsMZy4kWZsReW9C9PE8rctZeiWTZDXugA5nF4/s1600/distancetool.jpg (Sonic Electronic Measuring device image)
• https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-y_46xOvOmvx65uvbPfNQR17CxgaT-k5NN13LjvqFJNBVh4QELbtZuBPdUD1bu0TJf5NUbGJEpToJxICqJBKgCF7A2RGgwx8V1p6k7i80N58-Emb2Mkn9RnUHdtODqZ6dShKj7pqi3Rg/s1600/compass.jpg (Suunto Compass image)
• http://2.op.ht/365-240-ffffff/opplanet-laser-technology-trupulse-360b-01.jpg (TruPulse image)

(Look at Tim Condon's page "Field activity 4: Distance Azimuth Survey" for help)