Distance Azimuth Survey Method Activity

Introduction

This activity was conducted in order to learn how to conduct a survey using the concepts of distance and azimuth (direction).  These methods can be used to fall back on if other more advanced technology is not being reliable.  It works in many different circumstances and conditions and is quite simple, so knowing these methods could end up becoming useful in the field.

The objective of this activity was to work with a partner to collect spatial data in the field with a partner and create a map of the location and other attributes of the chosen trees.

Definitions:
Distance - the amount of space between two objects.

Azimuth - the horizontal angle or direction of a compass bearing.

Circumference - the girth or distance around an object.

Diameter - the distance of a straight line passing through the center of a circle to each side of the circle.

Methods

For this activity the two partners chose two sites along Putnam Drive on UW-Eau Claire's campus from which to locate, measure, and collect data about ten trees nearby.  The site map in Figure 1 shows the location of my group's two chosen sites.  The conditions of the day were sunny, humid, and warm, with most of Putnam Drive being shaded by the forest.

Figure 1: This site map shows the location of each site on UW-Eau Claire's lower campus along Putnam Drive.  

The tools used included: measuring tape, compass, GPS Pro device, distance laser, field notebook, and camera.  These items are shown in Figure 2.  The measuring tape was used to measure the circumference of the tree.  The compass was used to find the azimuth from the origin point to each chosen tree.  The GPS Pro device was used to mark the location of the origin.  The distance laser was used to measure the exact distance from the origin point to each chosen tree.  All the information collected was organized and recorded in the field notebook, and the camera took the pictures for the report.

Figure 2.01: The measuring tape was used to measure circumference of the trees.

Figure 2.02: The compass was used to find the azimuth.  

Figure 2.03: The GPS Pro unit was used to mark the point of origin.  

Figure 2.04: The distance laser was used to measure the exact distance from the point of origin to each tree.  

Site 1 was chosen by setting down the leather compass case and recording the coordinates of that spot with the GPS Pro.  This can be seen in Figure 3.  One student would stand directly above that spot and hold the distance laser to his/her chest and point the laser at the desired tree to get the distance to the tree.  That same person would stay in the same position and use the compass to find the azimuth from that spot to the same tree.  The other student would at the same time go to each tree and use the measuring tape to find the circumference of the tree and also try to determine the type/species of the tree if possible.  All this information was recorded in the field notebook.  This same method was used at Site 2.  One tip for recording trees is to go in order in one direction, say from left to right.  This way if any attributes are missed you can easily find which tree you need to remeasure or what have you.

Figure 3: Morgan is using the GPS Pro to find the location of the point of origin at Site 1.  

Once all the tree data was collected it was then manually put into an excel sheet, as shown in Figure 4.  The circumference was then used to find the diameter of each tree using a simple formula.  Also since the angles that the compass gave were divided into quadrants, each azimuth must be calculated into the corresponding angle within 360 degrees, with North being 0 degrees.

Figure 4: This image shows the excel sheet that was created to organize the data collected in the field.  

Next, a database was created using ArcCatalog as a place to import the data in the excel sheet as a table and to store all the results.  Each point was then brought onto the map by right clicking on the table in the table of contents, and setting the x field as longitude and the y field as the latitude.  The geographic coordinate system should be set as GCS_WGS_1984.  This can be seen in Figure 5.

Figure 5: This is the step to display the XY data as points on the map.  

Next the Feature Vertices To Points command was used to create a feature class containing the location of the trees as points.  The search bar was used to find this tool, as shown in Figure 6.  A basemap was also added to give context to the location of the points and the sites.

Figure 6: The Search bar was used to locate and use the Feature Vertices to Points tool. 

Then the Bearing Distance To Line command was used to connect the points of each tree to the origin point with a line, which was also found using the Search bar as seen in Figure 7.

Figure 7: The Search bar was used to locate and use the Bearing Distance to Line tool.  

Now that the data has been mapped it can be made into a more aesthetically pleasing map to be used to analyze the accuracy of the methods used in this activity.

Results

Figure 8 shows the final map created in ArcMap.

Figure 8: This is the final map result of the collected data in the field.  

This map shows that the point of origin for Site 1 was not accurate.  Each site has on the actual dirt road, and Site 1 in the map shows it being in the woods, off the road.  Site 2 seems to be accurate.

Because all the trees chosen in this activity were deciduous and the exact species of every tree was not known, the type was not specified in this map.

The distance and angle of each tree's azimuth in reference to the point of origin seems quite accurate however, and representing them by size was easy to display using ArcMap.

Conclusion

The azimuth distance survey methods incorporated in this activity were useful in locating features around a given point of origin.  The precision of the GPS unit will however affect the accuracy of the final product when brought into ArcMap.  These basic methods could be used in the field if the more advanced technology fails.