Survey Using Distance and Azimuth

Introduction
     The point of this lab is to use survey equipment to find exact location of tress in real life. This method of Distance/Azimuth surveying is an excellent way to survey the locations of objects in real life without using GPS units. It is also a good back up plan for when equipment fails in the field. The study area for this project was in Putnam park, a park that runs through the University of Wisconsin - Eau Claire lower campus.

Methods
     Equipment
     - Laser Distance Finder
     - Distance Finder
     - Compass
     - GPS Unit
     - Notebook and Pencil

     The compass is a device that is able to find North and can measure the azimuth from north. The Laser Distance Finder is the most high tech device that was used and it can measure the distance that something is away from the user, the azimuth of that object, as well as variety of other things. The distance finder is a two part device that contains a transmitter and a receiver. The transmitter sends out a signal that is received by the receiver. The receiver is able to measure the distance that the signal traveled. The notebook and pencil were used to take notes in the field.
     The Distance/Azimuth survey method is a method that is very convenient when their is a lack of advanced technology. It is a simple matter of setting up a survey area. Then using a simple GPS unit or a smart phone, if their is service, to get the location of the origin point. When the origin point is set find north. North will be the starting point, or 0 degrees, in measuring the Azimuth. Next step is to find the location of the object that needs to be mapped. Use the compass or laser distance finder to get the Azimuth or the degrees away from north that the object is. The next step is to find the distance from the origin point that the object is by using a laser distance finder or a distance finder. With the latitude and longitude of the origin point, the azimuth and the distance of the object from the origin point it is possible to create a map of the tree locations without GPS. 10 tree locations were taken from three different origin points. The point to the furthest north and the middle origin points used the Laser Distance Finder to find the location of the 10 trees, while the last location used the compass and distance finder to get the location of the trees. The attributes that were collected include the origin latitude and longitude, the distance from the origin point each tree was in meters, the azimuth of each tree in degress, the diameter at breast height (DBH) in centimeters, and the tree type. A portion of the data is displayed in figure 1 below.

(Figure 1: A table containing all of the attribute data needed to map out the locations of trees in Putnam Park.)

      The data was collected in three different groups and compiled into a google docs spread sheet. This data was then download and imported into ArcMaps. The Bearing Distance to Line tool was used to create a feature class of lines from the origin point to the location of the trees. The other tool that was used was the Feature Vertices to Point tool. This created a point at the end of each line that represented the location of the trees. Figure 2 below is an image of the data flow model that was used to create the features used in the map.

(Figure 2: A data flow model that shows the progression of the data from the original google docs table through both the Bearing Distance to Line tool and the Feature Vertices to Points tool.)

Results
     There was one major issue that occurred in this project. The second origins latitude was incorrect and the features appeared in the parking lot 20 meters north of the actual location. This problem was remedied by trial and error. The latitudes were lowered slightly to try and get the features in the proper location. Figure 3 is an image of a map that show the incorrect positioning of the second origin point.

(Figure 3: A map of the incorrect positioning of the second origin points group of trees.)

This map shows a group of points and lines north of the park and on the edge of the parking lot. The actual location was in the middle of the other two groups of lines and points. The reason that the group of trees for the second origin point were not in the correct location could be due to a few reasons. The most likely is the ridge that forms to the south of this study area affecting the GPS device that was used. Which is another reason why this method is so important, the only technical device that was used failed one out of three times. Another possibility is that the latitude was marked down incorrectly. The second option is less likely due to the fact that numerous different people all wrote down the same latitudes and longitudes. Figure 4 below shows an image of the same area but with the second origin point with a more accurate latitude. 

(Figure 4: An image of the study area with a corrected origin point for the second origin point.)

Unfortunately even with the better location of the second group it is still not accurate. The longest line going in a northern direction should be to the right of the path going through the woods not to the left. So while this method can give a general idea of where objects are located relative to other objects, it is subject to the accuracy of the origin point. Other factors that may lead to inaccurate results include human error. An improper read of one of the devices will lead to wrong results. 

Conclusion

   Overall this method is excellent if a representation of where thing are in relation to other things is all that is needed. However if absolute accuracy is needed in measuring the location of objects this method is subject to many types of errors or inconsistencies that will through off the results but can be useful when in a bind.