GPS and Total Station

Background: 

Figure 1: Topcon Tesla Unit for GPS point collection of mall at
University of Wisconsin Eau Claire

for weeks 9 and 10 our class was tasked with the objective to utilize two different methods of collecting survey grade point collection of the campus mall area. Our first collection utilized the Topcon Tesla (survey grade GPS unit figure 1) and also the Topcon Hiper SR (survey grade elevation calibrator figure 2). The week that followed our collection with the Tesla we where then to survey the mall area with the Topcon GPT-3100W total station. The total station is a stationary survey grade unit that shoots a laser to a 2 meter high reflector that allows you to collect multiple points from without having to move you collection station. After the two collections where finished we where to generate two separate continuous surface models and determine the pros and cons of each collection method to determine the best fit for each collection. 

Figure 2: Topcon Total station used in our second collection of
the mall of the University of Wisconsin Eau Claire

Methods: 

In week nine we where set out with the Tesla to collect a total of a hundred points within a 25 x 25 foot plot. Although our collection was easy there was a few stepping stones we needed to overcome before we started the collection. First was that we needed to connect to both the WiFi and the hyper unit in order to be able to collect elevation. We had a lot of complications with the connection and found that you first needed to turn on the Tesla unit before connecting to either of the other two units. Once connected we then needed to create a job to store our collection points. This was also an issue for the licensing for the Tesla had recently been canceled and we where only able to collect a total of 25 points per job. Because of this we needed to make for different jobs to collect a total of 100 points. Once the set up was complete we where able to start collecting our points. To accomplish this we needed to make sure a couple of preliminary objectives where completed. First we needed to make sure the hyper was level by shortening or extending the legs of the Hiper unit. Once level you are able to see the leveling bubble inside of the black circle meaning you are now ready to collect the point (figure 3).

Figure 3: once the Hiper is level the bubble will be centered in the black ring. 

Once the Hiper is level and set you then can run the collection. There are two options available to you when collecting one is a quick collect that will take less time but is not as accurate for it will take less points and does not run as much for mathematical algorithms in the programming. The second is a complete collection which takes more points and will average out the points to generate a more accurate and precise point collection. For this survey we mainly collected using quick points to save time and also because of the situation we did not need extremely accurate points for this collection. Once all hundred points where collected we had completed the first task and the following week we then collected the other points with the total station.
The second collection with the total station was done the week of thanksgiving on November 23. This collection would only be a total of 25 points for we still did not have full access to the licensing and Dr. Hupy decided that we would understand the process enough after 25 collection points. To collect points using the total station the equipment you needed are the same as the GPS collection including the Tesla, Hyper and WiFi, and also needed the Topcon Total station. For collection you first need to use the Tesla and locate three points. The first is the occupation site. or where the total station will be set up. The other two are back site points for the total station to use as azimuth lines and can then figure out what the coordinates of your points are. Once these three site where located using similar methods as the GPS collection we then could obtain our remaining 22 points. when using the Total station you first needed to level the station over the station over your acquired occupational site. To level the station you need to adjust all three legs to get it rough leveled then by using the three nobs located at the base of the station head unit you will adjust two at a time rotating around in a clock wise circle only adjusting one nob at a time to level the unit. A word of caution would be to try and not move the knobs that you have already adjusted so you do not continue to level the unit. Once leveled you then can obtain your points this will be completed by one team member who will carry the reflector unit out to the point that you want to connect. That person will then hold the two meter high adjustable pole with the reflector unit level so the team member can focus the stations lazer into the reflector head. Once the station has been tartgeted to shot the laser at the reflector unit the point can be collected with the same options of either the quick or standard collection. The process will be repeated until all points are collected.

Results: 

Figure 4: spline continuous raster generated from the GPS collection

The results where very interesting for I could easily see how each method would be useful depending on specific situations. For example when using the Tesla for collection it was a simple process to travel to multiple points and simple move two legs to level the unit. Where with the total station  you needed to  refocus scope and initially set up a very cumbersome unit. Some other advantages the Tesla had over the total station was that the preliminary set up was quicker and easier to set up. However, the downsides of the Tesla unit was that it needed to have access to WiFi in order for the Hiper to operate, and the unit itself was very finicky when running. On the other hand the Total station did have its advantages over the Tesla and they where that collection was very fast once all of the initial set up was completed. 

Although our original task was to compare the generated continuous surface raster with each other it was very difficult to have a true comparison, for we collected four times as many points with the Tesla than the total station making it by far more detailed and accurate. The results are as followed with figure 4 showing the map generated by the Tesla and figure 5 being the map generated from the total station.. As one can see although we only collected 25 points with the total station the results are very similar other than varying in break lines. The general trend of where the slope begins and the low areas the total station generated impressive results with such a low sample size. 

Figure 5: Spline model generated from the 25 points collected by total station

Discussion/Conclusion: 

Both of the collections where very unique to themselves for each one produced different complications. From not being able to connect with servers, to not being able to focus the laser. Both units produced many challenges that needed to be overcome. With each unit being unique each one offered different options to collecting, although the Tesla was easier to set up I could see how over a longer time frame or if more than a hundred points needed to be collected the process would take a lot longer than the total station. If I had to pick one unit over the other I could want to use the Tesla fr you did not need as much equipment, the set up was easier and the collection could potentially be done with one person. It is because of the idea that similar grade surveying could be done with less people and less room for error I Personally think this is why that method is better overall. 

Equipment: 

Topcon Tesla GPS survey grade

Topcon GPT-3100W survey grade

Topcon Hiper

MyFi unit used for wireless connection

Reflector rod for total station