Topographic Survey vs. Total Station Elevation Survey Techniques

Introduction

Gathering elevation data using GPS can be done in many ways. In this lab we explored the use of using topographic surveying with a dual-frequency GPS and surveying using a total station. The topographic survey requires a tripod, Topcon telsa field controller, topcon hiper SR positioning unit, and the MiFi. The total station survey requires the topcon telsa field controller, topcon hiper SR positioning unit, the MiFi, and the Prism pole. Both methods have advantages and disadvantages which we explored in this lab.


Study Area

• Date: 12 November 2015 and 23 November 2015
• University of Wisconsin-Eau Claire Campus Mall (area between Little Niagara that run through campus and Schofield Admissions Building)
• Conditions: Partly sunny with some wind, Average temp. 44°F (retrieved from weather underground)

Methods
Materials
Topcon Telsa Field Controller
Topcon Hiper SR Positioning Unit
Topcon Total Station
MiFi
Tripod stand (with level)
Prism Pole

Figure 1. Telsa Unit

In order to start collecting data, the Topcon Telsa unit needed to be set up. We created a new job and entered the necessary information. Note that we used the projected coordinate system UTM 15N and recorded our units in meters. Otherwise, our group used the default settings while creating a new job.

For our elevation survey we created a code "ELEV" so that the points taken were recorded under this code and given a unique number.

After the job was created, we connected the Telsa controller to the Hiper unit using a blutooth connection. With the Hiper attached to the top of the tripod unit and the Telsa attached as well we could start data collection.

During the second part of the lab the total station tripod and unit was used and connected to the telsa unit through a blutooth connection. To achieve the connection a MiFi portable wireless device was used just like in the topographic survey.

Figure 2. Total Station Unit

Data Collection 
On the Telsa unit there are two ways to collect the data (precise or quick). We chose to have the telsa take the average of 10 points using the quick option. Each time we collected a data point we needed to move and level the tripod to collect accurate points.

We took 100 points throughout the campus mall. Our strategy for taking the points was to zig-zag the mall area and avoid the large stones (as they would skew the elevation data).


The second part of the lab we used the total station to take elevation data by setting up an occupied point, and one back site. The purpose of the occupied site is that you only have to level the total station once to collect points versus with the topographic survey needing to move the whole unit 100 times.

Figure. Leveling the total station

Twenty-four points were gathered using the total station method. The back site and occupied point were first recorded using the topographic method. This is done because the total station sits atop of the occupied point and uses the back site as a reference in case you want to collect data beyond the scope of the original occupied point.

Figure 3. Troubleshooting the
blutooth of the total station

To set up the total station we first had to level the whole unit using the three round knobs on each side of the unit. Later, we used the laser to ensure we were right on top of the occupied point.

Collecting data with the total station, it is required to find the cross hairs from the prism pole exactly in the middle while looking through total station lens. From there you are able to collect the point data by selecting the save button on the telsa unit.




Analysis

Figure 4. Successful data collection!

We imported the data from the telsa unit to a notepad file on a flashdrive. From there we were able to display the X,Y data. We set our header line as follows, Lat (Y), Long (X), and Elev (Z) to avoid confusion when exporting the data as a feature class.

For both the topographic survey and total station survey the kriging, natural neighbor, spline, IDW, and TIN tools were run for all of the points. In the topographic survey data from the entire class was used to display the elevation of the UW-Eau Claire campus mall area. In the total station lab only points from our group were displayed.

Metadata

Who: Ally Hillstrom and Morgan Freeburg

What: Collecting elevation data by using dual frequency GPS

Where: UW-Eau Claire Campus Mall 

When: 12 November 2015

Why: To practice gathering elevation data with GPS  

Metadata

Who: Josie Markham, Drake Bortolameolli, and Morgan Freeburg

What: Collecting elevation data using total station equipment

Where: UW-Eau Claire Campus Mall
When: 23 November 2015

Why: To utilize another way of collecting elevation data

Discussion

The topographic survey was an easy method of collecting elevation data, however, compared to using a total station unit, the topo survey was quite slow. Below in figures 5 and 6 are the spline analysis layered over a topographic basemap of the UW-Eau Claire Mall. I chose spline to represent both datasets because after analyzing all of the tools spline displayed the topography of the study area the best. 

The data analysis is similar in accuracy between the two methods. The total station map would appear more segregated if there were more points to run the spline analysis with. Because the accuracy is comparable, the total station method seems much quicker and you could gather many more points in less time than the topographic survey.   

Getting to the end point of the maps was no walk in the park, especially with the total station lab. In both labs my groups struggled to work the telsa unit. We spent a lot of time troubleshooting. This goes to tell it is necessary to be prepared for complications in the field. Regarding the total station data collection we had to go out to the field three times in order to successfully collect the elevation data. Each time we went out we would get stuck on the next step. 

Our first challenge was the blutooth of the total station would not hold its signal. We had all the equipment set up and ready to go; the blutooth was even conected to the telsa unit. Once we tried shooting our back site the connection to the blutooth was lost. After that we spent fourty-five minutes turning the telsa and total station on and off (alternating the order) and trying to find our mistake in the settings. 

The next time we went out to the field we had all the equipment set out again, blutooth connection secure and the telsa turned off and would not respond. Finally, our third time in the field we were able to correctly arrange the equipment and the connections, but the telsa would not capture the point. Thankfully, it took less time to figure out the issue was focusing the crosshairs, and we were able to collect all of our points. Through our frustrations we became experts in setting up the total station over the occupied point in one try and leveling unit, but the telsa is the object that held us back. Unfortunately, technology fails sometimes.

Figure 5. Points collected from topographic survey and analyzed using the spline tool of ArcMap. 

Figure 6. Points collected from total station survey and analyzed using the spline tool of ArcMap.

Conclusion

Even though my group had our fair share of frustrations through out this activity it was incredibly useful to see the difference between the topo survey method and the total station survey method. Once again we learned technology is not perfect and may take a lot of troubleshooting, but in the end when it does work it makes collecting data much easier and efficient. The advantages of the topographic survey was it could be carried out with one person and does not require as much initial set up time. Again, I would favor the total station even though it requires at least two people and has greater set up parameters, but the ease of collection after is so much more efficient.

Priory Navigation Maps: Part Two

Introduction

As a continuation from last week's lab we used the maps we created to navigate a predetermined course given to us only using a compass. It is necessary to be able to calculate the the correct headings, and know your pace count before embarking on a course where you only have a compass and map to lead you.

Study Area
Date: 26 October 2015, 3-6pm
Location: Land plot surrounding Priory Hall, 1190 Priory Rd, Eau Claire, 54701

Conditions: Overcast, Average Temp. 53°F

Methods

Figure 1. Creating headings and pace
counts for the course at the Priory. 

First, we were assigned a course based on a UTM grid scale. We plotted the points on our UTM maps we made of the priory the week before and double checked with our group members to see if we plotted them correctly.

Firgue 2. Distances measured
between each point to
calculate pace counts. 

Next, we chose a starting point. Since the parking lot had been updated since the basemap was created we chose to start at the Northeast corner of the Priory's garage. Here we sat down and worked out all of the headings to each point, and roughly calculated the distance based on the pace count, we had determined earlier. To find the headings we lined up the orienting lines with our UTM grid of the map and made sure the north arrow matched north on the map (we made sure that the compass was set to north with 0 degrees). Lines were drawn to and from each point to clearly see the path and to find the degrees of each point.  After, we used the ruler on the compass to measure the distance between each point to calculate the approximate number of paces would be required to each course point.

With this information we were ready to start our course. Matt was our leap frogger, who was pointed in the right direction and moved towards the next point. Alyssa was the pace counter for Matt, and notified me when Matt got to the destination or landmark. I was the azimuth controller; I would ensure the heading was correct and point Matt in the right direction.

Figure 3. A tree marked with
neon tape to identify the
course points. 

The course points were marked with neon colored flags on trees. Once Matt found a course point, I would first make sure the north arrow was "red in the shed" and then changed to compass to the correct degree bearing. It was very important that the base plate was stable the entire time, that the direction-of-travel arrow was pointing directly ahead of the person. To minimize the error of these issues, the compass was kept at chest height and not tilted, or turned side to side. Only by rotating my full body was the compass pointing us in to the correct path.

Metadata

Who: Matt Brueske, Alyssa Krantz, and Morgan Freeburg

What: Navigation to course points using a map and compass

Where: Priory Land, Eau Claire, WI (1190 Priory Rd, Eau Claire, 54701)

When: 26 October 2015

Why: To use the traditional method of compass navigation to locate course points

Discussion

When it came down to navigating the course, we ran into a couple of problems. At the very beginning while we were trying to plot our points, we noticed our maps did not have many decimal places to go off of forcing us to somewhat estimate the course. Also, we did not have divisions between the major grid lines. Minor tick divisions would have saved us a lot of time and effort trying to calculate the values in our head. Plus, this would have made our course more accurate on our map.

Figure 4. Looking from the northeast side of the
Priory garage towards our first course point... 

Another issue we faced was our starting point. Although it did not interfere with the orienting to the first point it was more of a mental obstacle to start with. By selecting the northeast corner of the garage, we had to send the leap frogger right through a patch of shrubs and smaller trees. This could explain how we did not exactly find our first point. We saw a branch with a neon flag, but we later realized the first point we were supposed to find was a little more to the west. The distance and angle were close so that is why we figured it was our first point, when it was only marking a trail.

Figure 5. Course point two not marked with tape.

Navigating to our second point was extremely difficult. The course took us through a forest of knee height shrubs and tree branches trying to stop us. The downhill path was difficult to count paces through and to even take a normal pace because of all the debris in the way. We had thought we had made the approximate amount of paces but could not see the marker in sight. We searched for around five minutes, trying to troubleshoot and double checking the compass. We ran into the other group completing course five also looking for the second point. We looked compared notes and looked for another ten minutes together. Finally, we consulted the GPS we were given only to use if we were lost, and determined the flag must have been lost. We picked a tree that was closest to the what he GPS said was the correct point and used that to head off to point three.

Figure 6. Challenge of counting paces downhill
and through trees and shrubs.

After struggling with the first to points, the rest of the course was fairly easy to navigate. We were excited when the compass pointed us in the right direction, only varying by a few feet or when the pace count was dead on. The difficulties from the rest of the course were trying to explain a landmark to the leap frogger when the only feature around was trees. The "tree" at that point did not serve as an accurate landmark and got quite confusing when they all appeared to be the same height and species. Sometimes it was beneficial to point out a landmark farther in the distance because it was easier to identify, however, if there was a communication error the leap frogger was off course. If we selected close landmarks it was more tedious and it seemed as though more obstacles were in the way. The final issues we faced were trees or poky plants slightly altering our course of direction by trying to avoid them as well as going up and down hillsides altering the pace count. We did not account for this and should be taken into consideration in future courses.


Track Log

Below you can see the path we took through trying to find the points using our map and compass. In the area that is dense with points, we were lost trying to find course point two (which we later found out was unmarked). The rest of the course, however, went somewhat smoothly, especially navigating through the dense (dark green) wooded area.

Figure 7. The track log from the GPS unit we carried with us through navigating the course. 

Conclusion

In conclusion, navigating is reliant on many little nuances that if vary even a small amount can throw you off course. A great map, proper use of a compass, and pace count are all essential in the successful navigation of any course. This activity showed the importance of ALL these elements and forced us to trouble shoot when we became a bit lost.