Lab 7/8 Topographic Survey

Introduction

The goal of this lab is to use basic topographic surveying equipment and methods to conduct a study on an area in the University of Wisconsin Campus Mall, between the Davies Student Center and Schofield Administrative Building. This lab was broken up into two major sections; the first section used the Hiper device to collect GPS field data. This section was done in a group of two where one person used the Tesla to record the points and the other person held the Hiper at the location of where the GPS point was being taken. The second part of this lab was done using the Topcon total Station and a reflective prism. This section was done using three people where one person looked/lined up the Topcon with the second person who was holding the reflective prism and the third person was working with the Tesla recording the points. Both of these exercises will teach us the basics of how to use Field Surveying equipment and also help us work with understanding different methods of collecting and exporting data.

Methods for Section 1

On the first day of working with the equipment, Dr. Joseph Hupy of the Geography and Anthropology Department at the University of Wisconsin Eau Claire taught the class how to use the equipment and delivered some tips which would prove effective once we took the equipment into the field. For this project we were going to have to gather 100 data points in the campus courtyard. This was done using four separate folders due to technical issues. In order to learn the proper way how to use the equipment which included using the Tesla and Hiper, Professor Hupy told us all the basics of how to set everything up and then instructed group 1 on how to set up all the equipment. In turn that group would then instruct the next group and so on until every group was familiar with how to use the Tesla and Hiper (image 1 and 2).

Image 1: Tesla unit used during our data collection

Image 2: Similar Hiper and Tesla unit we used during our field data collection used at an apparent construction site

The steps for this were;

                1.) On the main screen of the Tesla select the Magnet Field App

                2.) Create a new job, which is accessible from the Magnet Field Home Screen (select job)

                3.) Fill in all the information for the job. We used generic class and group names to make it                      easier for everyone to know which files were being used by which group.

                4.) Still in the new job information, several additional questions will pop up including                              Coordinate System questions and Configuration setup questions.

                5.) Using the Bluetooth capabilities, fueled by the Verizon Wireless Mi-Fi hot spot                                    (image 3), connect the Hiper to the Tesla unit.

                6.) Now we are ready for data collection. We used the code name ELEV for elevation and                        used a specific group of points so we do not experience any overlap from other groups                        once all the points are merged together.

                7.) Make sure data collection is on Fixed only. We used an average of 10 points per data                          point collection

                8.) Once all data is collected and saved, you may disconnect all the equipment and return to                       the Magnet Field home screen to export the data

Image 3: The Verizon Wireless Hot Spot, a similar model was used in the field while we were outside collecting data

While in the field collecting data one person worked the Tesla Unit while the other person made sure the Hiper, seated atop a 2 meter stand, was perfectly level while the data was being collected. Casually going through a section of the Campus Mall we collected a total of 100 data points. By hitting the save button on the Tesla Unit, it would take 10 points from the one spot and then average the points out and save it as one point. Once concluded, we exported the four files onto a jump drive. The txt file exported contained information on the northing and easting direction as well as the elevation from the point. This txt file can be imported into ArcMap and turned into a map (figure 4).

Image 4: The final product of the Hiper/Tesla data collection 

Discussion for Section 1

When looking at the map created by taking our data points we see as we move from the right side toward the left the elevation is decreasing. It is only about a 2 meter decrease but in our small study area it is seen as a large change in elevation based on the color scheme. Also as we move from the top right of the map to the bottom left we see the elevation continuing to decrease. Overall, it is clear that the campus mall is sloped downward toward the Little Niagara Creek. When looking at an aerial image of the area one would think the center circle of the amphitheater would be the lowest part, but in fact it is the area just to the east of the circle which is the lowest according to our data.

Conclusion for Section 1

In conclusion I would say that this was a fairly quick method, once all methods have been learned, to collect data. It is accurate and easy to learn. Since our study area was not done using a basic GPS tool it is difficult to say which was better at collecting data. As for the campus mall, although not a study question for this lab and something that came to a surprise to me, the circle at the center of the amphitheater is not the lowest point on Lower Campus mall, not including the land by the creek which can easily be seen as lower.

Methods for Section 2

This part of the project as mentioned in the introduction was done using three person groups. Again we spent the first part of class learning about how to use the proper equipment. To start off our learning experience we talked about what all was going to be done in the class room and learned some basics about how to use the surveying equipment and some basic terminology. Using the same study area as section 1 we had to gather 25 data points. These 25 points also include 1 backsight point and 1 occupation point.

                Occupation Point: It is the point of where the Topcon Total Station will be used

                Backsight Point: It is a point taken back towards a point of known elevation, it is used to                calculate the height of the surveying instrument.

The backsight and occupation points had to be collected using the Hiper and Tesla devices. Using the same methods as used in section 1 to collect points, the two points were collected and labeled correctly so we would know when processing the data which points were which. After the data was collected we could begin working with the total station. The first part we had to do was set up the tripod for the total station to be set up on. It was comprised of three legs with large stakes at the end of the legs to assure it would be able to stay firmly on the soft ground. Once the tripod was set up the total station could be screwed into the stand using a metal connector which screwed into the bottom of the piece of equipment. Once the equipment was at the desired height a laser was shot out the bottom to show the exact point it was above. Because we set our occupation point to a specific spot, we had to assure the laser was directly above that. Once at the correct height, we had to measure to make sure we knew the precise height of the total station above the ground. We used the elevation of 140 cm or 1.4 meters above the ground (figure 5).

Figure 5: The total Station set up and ready to be used for data collection

The next step was to make sure the equipment was completely level to assure the most accurate data collection. This was done by moving the legs up and down, one at a time, and using knobs beneath the total station. Once level we could begin collecting data. In order to collect data, the total station shoots out a laser toward the reflective prism, which is at an elevation of 2 meters.

Before shooting data points, all the equipment had to be connected via Bluetooth using the Verizon Wireless Mi-fi. This was done similar to the section 1 connection. This section proved to be the most difficult part of the exercise, will address issues in the evaluation of lab 7/8 in the assessments tab.

In order to collect the data points, one person would line up the total station view finder with the prism at a different location. Once lined up, the person working the Tesla Unit will capture the data by hitting the save file button on the Tesla, this would be done 23 times, in order to collect a total of 25 points. While working we experienced so many unable to capture data points and data points captured that we wouldn’t even have to talk instead we would just listen to the beeping sound the total station would make. A triple beep became our best friend in the frigid weather. Triple beep indicated a successful data capture.

Once all points were captured, we exported the file as a txt file, similar to how done in section one and would be used to create a 3D and a 2D view of the data.

Discussion for Section 2

The data once again put into a txt file was imported into ArcMap to create a visualization of the study area. When looking at the map created we see the elevation decreases as we move from the right side of the map to the left side. We also see as we move from the top of the map to the bottom of the map a decrease in elevation. The area around the Little Niagara Creek as expected is the lowest area in the study area, and the circle which looked like it was not the lowest point in section one, is confirmed not to be the lowest point on the map. The Occupation point was marked using a Green Flag to represent the starting point, and a checkered flag was used to mark the backsight point, not because it was the final point, but just to fit the theme of flags being used to mark the points (image 6).

Figure 6: The totalstation data captured in the field portrayed in a 2D map using ArcScene

A three dimensional map was also created, using the kriging method of data interpolation in ArcMap, a raster file was created and imported into ArcScene. In order to better see the change in elevation, I changed the exaggeration to 6.0. The image shows the higher elevation is away from the creek and as we get closer the elevation gets lower. There is only about a 3 meter difference between the highest point on the map and the lowest (image 7).

Figure 7: The 3D view of the total Station data captured, using ArcWorld to display data

Conclusion for Section 2

In conclusion I would say that this was a difficult method to learn and get used to, but once we learned how to do everything we became very quick at capturing data points. This method again if we could compare it to other methods in the same study area I could have an opinion on the accuracy, but since we did not do this I cannot say which is more accurate, but can assume this way is much more. Overall, this was a great method to be able to add to our collection of surveying techniques and like the other survey methods conducted, this one serves a particular purpose and is best suit for certain fields while other methods have strengths in different areas.