With the advancements in Geospatial Technology, many new and innovative techniques are available to complete surveys and collect data. In this lab, we were able to collect data using two methods. These methods included the Topcon Tesla GPS Unit connected to a Hiper SR Receiver and the Topcon Total Station. Both methods are great for topographic surveys, but both definitely have their pros and cons.
Study Area
The study are for these studies was the University of Wisconsin-Eau Claire (UWEC) Campus Mall area (Fig 1). This is an area that is very wide open and includes elevation changes that can be easily surveyed. Our first area surveyed with the Topcon Tesla was the Little Niagara Creek banks along the campus mall area. The second area surveyed with the Topcon Total Station was the green space of the campus mall. Both days of data collection were Partly Cloudy, and mid 50 degree weather.
Figure 1. Aerial image of UWEC campus mall area.
Methods
The objective of both of these tomographic studies was to collect elevation data. The first study used the Topcon Tesla GPS Unit (Fig 2) that was connected to the Topcon Hiper SR (Fig 3) thru a Bluetooth connection. This connection was possible by using a wireless 4G connection available through the local cell provider.
Figure 3. Example of the Topcon Hiper SR Positioning Unit.
The Tesla and the Hyper SR were both mounted to a survey pole (Fig 4) that made data collection easy and accurate. To start data collection, a new job had to be made on the Tesla unit. By creating a new job, the job has a unique name for saving and options for coordinate systems and projections. For this exercise, our group created a job called GROUP6_TOPO. Once the job is set up, it also allows you to set the connections you will be using to collect data. In this case we wanted the Tesla to connect to the Hyper SR through the Bluetooth option.
Once the job was created and all connections made, it was now time for data collection. The Survey tool on the device was used, then the Topo option. The device lets you create a personalized point number and also a classification for the point. There are preset classifications that can be used or you can create your own depending on what you are collecting. We were collecting elevation data, so the ELEV option was chosen.
Now that the device is ready for data collection, the pole (tripod) must be properly leveled and the "Save" button on the device can be hit to collect the data point. In the options we set the device up to collect 5 data points then average them for the final value.
We were to collect 100 points from any area on the campus mall. We chose to do the Little Niagara Creek embankments.
Figure 4. A field technician collecting data using a similar Topcon Tesla and Hyper SR system. In the study, we also used a similar GPS rod to hold and position the device for accurate data collection.
The second part of the study used the Topcon Total Station (Fig 5) to collect elevation points. The Total Station stays in one location on a set-up, leveled tripod over a predefined point (Occupied Point) . For the device to work, a Backsight point must be set for the device to define which way is north for proper mapping. To set the OCC and the Backsight points, we once again used the Tesla and the Hyper SR. There are other techniques that could be used like a predefined point set in a field or location, but in our case this was the easier method to use. Once the OCC and Backsight points were taken and marked, it was time to set the Total Station up.
The tripod for the total station needed to be set up directly over the OCC point. First it is best to rough set up the tripod and firmly attach the total station to the tripod. By turning on the Total Station and selecting the laser from the option menu, the laser from the Total Station to the Ground can be turned on. This laser should be right on the OCC point.
Next, we needed to turn on the Bluetooth. Just like with the Hyper SR Unit, the Total Station is also connected to the Tesla Unit by Bluetooth. Like in Part 1 of the exercise, we wanted to create a new job and choose the Total Station as our connection. It is important though when setting up the job that the points are set for the OCC and the Backsight. Since the Total Station also uses a Prism to collect data, you must also enter the height of the Prism rod. In our case, it was 2m. The last interval to enter is the distance from the ground (the OCC point) to the established marker line on the Total Station. These all play a vital role when the Total Station is collecting the data points.
Now that the set up work is finished, just like earlier the Tesla will be used since it is connected to the Total Station. One partner must take the Prism rod to the point of interesting and level the rod straight up. The second person must alone the optical of the Total Station to the Prism Rod and hit the Save button on the Tesla for the point to be collected. The Total Station will send a beam to the Prism rod, which then will be reflected and collected.
Once data from both parts of the exercise were collected, the data was loaded off of the Tesla Unit in a text file (.txt) (Fig 6/7). This file can be easily imported into a geodatabase and loaded into ArcMap by using the Add X-Y data option (Fig 8). Once feature classes of the data were made, the IDW raster interpolation method was used to see the elevation differences of the area surveyed.
Figure 5. Example of the Topcon Total Station used in the second week of the study.
Figure 6. The original text file downloaded from the Topcon Tesla Unit after the first data collection exercise.
Figure 7. The original text file downloaded from the Topcon Tesla Unit after the second data collection exercise. The Total Station was used for collection, but the Tesla Unit received and stored the data.
Figure 8. Screen shot of the "Add X-Y Data" window that was used to import the text files and create a feature class of the data. The X/Y fields are the Longitude and Latitude Values, while the Z value is the height (elevation).
Results
The results of the survey show small elevation changes in both areas. Looking at the scales of both maps, you can see that the changes are within 1 to 2 m. The Little Niagara Creek banks did not show up as steep on planned, but changes can be seen from the base to the top (Fig 9). By using ArcScene, this IDW data was also loaded to make a 3-D image (Fig 10.)
The survey of the Campus Green Space showed rising elevations as we moved farther away (Fig 11) This was due to the banking of the landscape near the library and Schofield Hall. This could also be due to having water flow downwards towards the creek.
Figure 9. Map of the elevation data of the Little Niagara Creek banks on the UWEC Campus Mall. The data points were processed using the IDW raster interpolation method and collected using the Tesla and Hyper SR units.
Figure 10. Image of the IDW data in ArcScene for 3-D visualization. The lighter the color, the lower the elevation. The white shows the creek, while the darker purples are showing the embankments.
Figure 11. Map of the elevation data of the UWEC Campus Mall green space. The data points were processed using the IDW raster interpolation method and collecting using the Total Station.
Discussion
Both methods were able to easily collect topographic data, but both definitely had their pros and cons. The Total Station definitely has a lot of set-up time and implications, but once collecting data it is easy to use. Another con of the Total Station is that it requires two people to operate. By the unit staying in one place, the Prism is much lighter to carry and also the Bluetooth signal does not flux since the unit stays put.
The Tesla and tripod were easy to set up and can easily be used by one person. It is much accurate since multiple points can be taken and averaged for a final value, but this also requires you to be steady. The tripod is easy to move around, but is heavier to carry and sometimes you can have trouble keeping the Bluetooth signal connected.
Overall, I thought that this exercise was very knowledgeable. These are both common ways of completing surveys and depending on the company you work for it could be one or the other.
Both methods were able to easily collect topographic data, but both definitely had their pros and cons. The Total Station definitely has a lot of set-up time and implications, but once collecting data it is easy to use. Another con of the Total Station is that it requires two people to operate. By the unit staying in one place, the Prism is much lighter to carry and also the Bluetooth signal does not flux since the unit stays put.
The Tesla and tripod were easy to set up and can easily be used by one person. It is much accurate since multiple points can be taken and averaged for a final value, but this also requires you to be steady. The tripod is easy to move around, but is heavier to carry and sometimes you can have trouble keeping the Bluetooth signal connected.
Overall, I thought that this exercise was very knowledgeable. These are both common ways of completing surveys and depending on the company you work for it could be one or the other.
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