Activity 9: Surveying with a Topcon Total Station and GMS-2 GPS Unit

Introduction

The last couple of weeks we have been working on two different but very similar projects. Dr. Hupy assigned us to use a couple of different pieces of technology to collect elevation data of the campus mall here on the UW-Eau Claire campus between the Davies student center and Schofield Hall. The two different equipment pieces we used were the Topcon Total Station (Figure 1) and the Topcon Tesla GPS unit (Figures 2,3,4). With both of these pieces of equipment we were to collect elevation points and create interpolated surface maps with the results of each and compare the two methods of data collection. A previous activity where we collected distance/azimuth data is a simple way to do what we are doing with these high tech units however we did not collect elevation data which is vital for creating interpolated surface maps. These high tech units increase accuracy in most cases and give you that important elevation measure at a very high accuracy. These high tech units are costly however. They are expensive costing thousands of dollars and it is very time consuming and inconvenient because of the amount of equipment you have to bring with you to conduct the survey and collect the data. The complexity of these units is much greater as well so knowing when to use them compared to just doing a simple distance/azimuth survey is important.

Figure 1 This is the total station. It is used to conduct a surface survey as it can provide distance/azimuth and elevation data with high accuracy. This is a very pricey unit with a cost of 5 to 6 thousand dollars.

Figure 2 This is the Telsa GPS survey grade unit. This is the main console with all the different programs and tools installed on it. It is both WiFi and Bluetooth enabled which is why we need a MiFi console Figure 4. This is where you create files to store the data collected.

Figure 3 This is the GPS part of the unit. This communicates with the console above through Bluetooth. This will give you 2 to 3 millimeter accuracy of the location of data points being corrected. Elevation or Z values are also very accurate when collected with this unit.

Figure 4 This is a MiFi unit. This uses a 4G cellular connection to provide WiFi signal for up to 15 devices. This is used with the Tesla unit to increase location accuracy and enable wireless data transfer.

There is alot of new technology and processes to learn for this activity and that is why we spent basically a whole class period learning from Dr. Hupy how to operate these units. Set up and use of these units is a little tricky and needs to be repeated a couple of times before the work flow becomes easier. First we started with a general overview of the units and their purpose and Dr. Hupy emphasized the importance of being careful with them and handling them with care because they are very expensive. Another key point he emphasized is the importance of making sure both the Tesla and total station are level when data is being collected. This takes time. Through adjusting the tripod legs and black knobs on the total station it is leveled and when using the Tesla just tilting the pole until the circle level is inside the ring will do the same. The total station was definitely more difficult to level off. After the units are leveled Dr. Hupy explained how to collect the data which I will explain later in the Methods section of this post. 

Each group was to collect 50 points per person with the Tesla GPS unit and as many as we saw fit with the total station. My group collected 150 with the Tesla and 50 with total station. This data was then imported into ArcMap and surface maps were created from it.

Study Area

The area Dr. Hupy wanted use to collect data in is what we refer to as the campus mall Figures 5. It is a large open area in the middle of lower campus. It is fairly flat for the most part with little elevation variation however the whole area is pitched towards the south and the Little Niagara Creek Figure 6 that runs through lower campus next to the Davies student center. This activity was delayed because of  rain and poor weather in which these units should not be used in. The days data was collected were sunny spring days in the mid to upper 60s with little wind.

Figure 5 View of the campus mall from the occupy point during our total station data collection. Schofield Hall is on the right and Davies Center is on the left with the library at the end.

Figure 6 Little Niagara Creek runs through the middle of the campus mall past Davies Center.

Methods

Total Station Collection

First step to collecting our data was check out the equipment from the Geography department here on campus. We then walked from Phillips Hall to the campus mall to set up the total station. Before the total station was put in place and leveled two points had to collected with the Tesla. These two points are called the occupy and bascksight points. The occupy point is where the total station would be set directly above and stay during the duration of the data collection. The backsight point is recorded to give the total station a zero point from which to calculate the azimuth values. This backsight point is what the total station will record as North. Once the location of these two points is recorded the total station can be setup and leveled off to start data collection. The first step in setting up the total station is opening up and tripod that the station sits on. Then the station is mounted to the top and screwed into place. Then using the built in laser on the station we made sure that the station was directly over the occupy point location collected earlier. Once this is done then the tripod legs can be pushed into the ground and the leveling processing can begin. There is a circle level on the tripod stand and the key to making sure the stand is level is to get the bubble into the center ring of the level. This is done by slowly sliding the tripod legs one at a time up or down. Once the stand is level the next step is to level the total station itself. There are two tubular levels one on each side of the unit. There are 3 black knobs on the bottom of the unit at each corner. When turned these move the unit up and down slightly allowing you to level the unit. 

Once the unit is leveled the collection can begin. The total station is connected via Bluetooth to the Tesla console (Figure 2) which caused a lot of headaches for most groups. Once connected a new job is created where the data points will be stored. In order for the collection locations to be accurate the occupy and backsight point are entered in the file setup. It also asks for a height of the station off the ground as well as the height of the reflector (Figure 7) off the ground. In our collection the total station was 1.55 meters off the ground and the reflector was 2 meters up. Making sure these heights stay consistent during data collection is vital for accurate elevation measurements. Once this is all set up point collection begins. 3 person groups are ideal for this exercise so that one person can focus the total station, one can walk with the reflector pole and one can record the points in the Tesla console. Point collection was fairly easy after setup was complete. To collect a point the person holding the reflector picks a location and then holds as still as possible facing the reflector as straight back at the total station as possible. The person at the total station then uses the top sight to find the general location of the reflector. Then looking through the scope and using the adjustment knobs to move the scope up, down, left and right the cross hairs are placed on the center point of the reflector. Once the crosshairs are locked on the person on the Tesla console taps the collect point button. The total station will then collect the azimuth, distance and elevation for that point. This process is repeated for as many points as the user desires. We collected 50 points in approximately 30. Getting the crosshairs locked in is the most difficult and time consuming part of collection but the more you do it the better you become at locating the reflector and locking on.

Figure 7 This is the reflector that the total station shoots the laser beam at to calculate distance when taking the survey. It is hard to see but there are 3 lines that intersect in the middle of the scope and that point is where you want to line up the crosshairs of the total station scope on to get an accurate reading.

Tesla GPS Collection

The data collection with the Tesla GPS unit was much simpler and quicker. The GPS unit Figure 3 is mounted on the tripod with the MiFi velcrod to the pole and console either attached to the pole or carried. The MiFi, GPS and console are all powered up. Once the console is connected to the MiFi connection the GPS can be connected to the console via Bluetooth just like with the total station. Once everything is connected the next step is to create a new file to store the collected data in. Then inside that file collection begins. In order to collect the points the tripod is leveled using the circle level attached to the tripod. Once it is level all you have to do to collect a point is tap the collect point button on the console. We did this for a 150 points throughout the mall. It took about 2 hours to collect the points just because there were so many. The setup is simple and collection is easy.

Results

Once the data was collected using each method the files were dumped onto a computer in the form of a text or .txt file. This files include the latitude, longitude, height and name of each point that was collected in the field. Once the text files are of the console they are imported into ArcMap. They show up as a bunch of points on the map but when the interpolation tool is used a surface elevation map is created in both 2D and 3D. Figures 8,9,10 and 11 below are the resulting maps from the two surveys.

Figure 8 This is the interpolation of the points collected with the Tesla GPS unit. I used the Kriging interpolation method to create this map. You can see the elevation change of the campus mall from this 2D map.

Figure 9 This is the interpolation of the points collected with the total station. I used the Kriging interpolation method to create this map. You can see the elevation change of the campus mall from this 2D map.



Figure 10 This is the 3D surface map of the campus mall collected with the Tesla GPS unit. I exaggerated it by 2 to make the elevation change more apparent because it is really hard to see using the actual elevation values. This unit captures the surface a little better probably because there are 3 times the number of points in this model than there are in the total station model.  As you can see the campus mall is a pretty flat area.




Figure 11 This is the 3D surface map of the campus mall collected with the total station. I exaggerated it by 2 to make the elevation change more apparent because it is really hard to see using the actual elevation values. This representation isn't as accurate because there are much fewer points used in this model. The weird point that is in this image is most likely where the total station was sitting while collecting this data. That point is obviously an error created by ArcScene.

Discussion

Both of these units and data collection methods are important to know how to do and very applicable in real world situations. One is obviously easier to do than the other. The total station has a much higher cost associated with it. Not only does it cost a large amount of money but the time and knowledge that is required to use is also very high. The frustration and time wasted while trying to get it all set up properly and get everything on the total station and the Tesla console to work together was a big annoyance and set back. It took us about twice as long to get everything set up and working than it did to collect our survey data. This goes back to what Dr. Hupy told us a couple of weeks ago that the more technology you are relying on the better chance that it won't work. That is why knowing how to do a distance/azimuth survey with very little technology is a good skill to have. Even when Dr.Hupy was doing demonstrations in class of how to use the units they weren't always working right. He wasn't doing anything wrong that is just what happens many times when working with high tech equipment. The biggest problem we ran into is getting the Tesla console to connect to the total station via Bluetooth. I turned them both on and off a couple of times before they finally connected to each other. Once it was connected everything went smoothly. Setting up the tripod for the total station was also a little tougher than I thought it would be. Getting it level was difficult. Overall the total station is a longer more involved and frustrating process.
Using the Tesla GPS was much easier in my opinion. Everything connected the first time we tried and with this unit one person could have collected all the data. You don't need three people. The data collection went much faster because you didn't have to find the reflector every time you collected a point. Getting the tripod level was the biggest part of the work for this method. This process can be sped up by not using two of the legs on the tripod and just using the center pole with the level on. Simply holding that middle pole and leveling it allows you to move much more quickly than trying to level out all three legs at every point. Being careful to keep the pole steady while collecting the points is the biggest concern when collecting data in this way. The Tesla GPS overall was much quicker and user friendly in my opinion there was much less equipment to bring with you, fewer moving parts, less back and forth between devices and less human input required.

Conclusion 

This semester we have now learned the low tech way (azimuth/distance) and high tech way (total station and Tesla GPS) to conduct a survey. Both ways have advantages and disadvantages and the usefulness of each is dependent on the situation. However if it is accuracy that you want which is the case most of the time I would chose the high tech method. Even though it can be more time consuming and frustrating the results tend to be much more accurate and reliable. It also provides you with elevation data without which creating surface models like we did in this activity would be much harder or even impossible. This activity taught us how to use these new technologies, work together in teams and again do some more work in a GIS sharpening those skills. Overall a good exercise it was frustrating at times but the end result that can be created from this highly accurate data what makes the activity useful.

Activity 8:Conducting a Distance Azimuth Survey

Introduction

This week Joe Hupy gave the class the assignment conducting a survey through the use of the distance and azimuth method. The most important part of this method is finding a base point. Once you have that point it is used to map out all the features in relation of distance and azimuth to it. This is a low tech method that can be used when technology and more advanced methods fail or are not possible. This could be caused be bad weather like extreme cold or hot temps that cause the instruments to malfunction or something as simple as running out of battery. Technology does and will fail and this method gives you an easy and effective alternative. There a couple of different ways the data could be collected for this exercise. You could two separate instruments to find the distance and azimuth such as a range finder (Figure 1) and a compass (Figure 2). In our case we got to use a instrument that can do both at the same time. This was very handy and a big time saver. We used a TruPulse laser (Figure 3).


This is a Vector Optics laser range finder. By looking through the lenses and placing the crosshairs on your target it will read the distance you are from that object. (Figure 1)



This is a Suunto compass. You can find azimuth by looking through the hole on the compass and when you point it at the object you want to find the azimuth for it will display in that hole. (Figure 2)

This TruPulse laser unit will find both azimuth and distance at the same time. These are the units we used for this exercise. (Figure 3)

Joe Hupy took us outside into the Phillips Hall court yard here on campus and gave a quick demo on how to use this equipment. He then split us into our groups for the week and gave us the assignment. We were to find a study are that was 1/4 to 1 hectare in size to collect our data in. In this area we were supposed to collect at least 100 data points recording their distance, azimuth and a couple other attributes of our choice for each one. After the data is collected it will be imported back into ArcMap where it will be used to make maps of the collected points.

One thing Joe told us to consider is Magnetic Declination. It is the angle between magnetic north and the true north which changes as the earth's magnetic field varies based on location and time. I looked on line and found a website dedicated to Magnetic Declimation values based on your search location and it said that on the day our data was collected the declination for Eau Claire was one degree west. This means our recorded data will be one degree less than true north. This isn't a huge factor here in Eau Claire but in other areas of the world this declination value can be much higher.

Methods

Study Area

The first step of the assignment and data collection was to choose a study area. Our group decided that the parking lot area behind Davis Center and Phillips Hall here on campus would be a good location (Figure 4). We were interested in collecting car data so this was a very well suited location. There are lots of cars in a relatively small area making the collection of 100 points pretty easy. In order to find a base location we opened up Google Earth and looked for easily identifiable objects in the this area that would also give us a good view of the parking lot. We also found the latitude and longitude for our base locations which will be used at a later time in ArcMap when creating our maps. We determined that one of the statues behind Phillips Hall and a sewer cap down by Davis Center would be the best location for our base points. They were both raised platforms which made the cars easy to see and not only see one row but multiple rows of cars. Figures 5 and 6 are panoramic views from our two base locations.

Figure 4
The red rectangle in the image shows our study area behind Phillips Hall and the Davis Center.

 

Figure 5
Panorama view of base point 1

Figure 6
Panorama view of base point 2

Survey Process

In order to collect our data and get values for distance and azimuth that were as accurate as possible we mounted the TruPulse laser to a tripod for stability and base point location accuracy. Keeping the laser unit in the same base location while collecting data is essential to getting accurate readings. We took turns locating cars and firing the laser to gather our distance and azimuth values. The other team member was recording these reading as well as our other attributes such as car color and brand. The distance was recorded in units of meters and the azimuth was collected in decimal degrees. We gathered the data in increments of 10 to 20 cars row by row to make it easy to keep track of what cars we had done. In some cases it was difficult to get the TruPulse to get an accurate reading on the distances of the cars. Shadows and reflection from the sun were likely contributors to this problem. Keeping the TruPulse steady was difficult at times as well which also contributed to less accurate or more time consuming readings.

 

Data Entry and Mapping

All of our data points were collected in a Excel spread sheet using one of the Geography departments Microsoft Surface tablets. Having that tablet in the field was super convenient because instead of having to write down the data and later transfer it into an Excel sheet we could do all that in the field as we went. Figure 7 a and b is the resulting Excel sheet which we then imported into ArcMap.

 

Figure 7b

Figure 7a

 

 

The first step of the mapping process in ArcMap was to add a basemap. This gives us a visual reference as to where our data points were collected. For my base map I used an aerial photo in the geography departments Eau Claire County data folder (Figure 8).

Figure 8
Aerial photo from Geography GIS data folder

 

 

Next a geodatabase was created to hold all the collected field data. This is where the Excel spread sheet will be imported to. We then needed to determine the location of our too base points. In order to do so we located them on Google Earth imagery and found location one to be 44.796908 N and 91.50104 W. Location 2 was 44.796408 N and 91.49952 W  (Figure 9).

 

Figure 9
Base points for data collection

 

Once we had our base locations we then imported the Excel spread sheet. In order to do this you right click on the geodatabase and hit import and then choose the Excel file. We now need to find the location of the surveyed features so that they can be mapped. We used the Bearing Distance to Line tool in ArcMap to do so (Figure 10). The tool takes the information in the Excel and turns it into a line feature class based on the an X and Y coordinate field (Longitude and Latitudinal location in decimal degrees), a bearing field or azimuth and a distance field. Figure 11 is the resulting map from running this tool.

 

Figure 10
Bearing Distance to Line tool

Figure 11
Line feature class generated by Bearing Distance to Line tool

 

This tool does not give you the actual location of the data points collected however for that a different tool must be run. Using the Feature Vertices to Points tool (Figure 12) in ArcMap points are placed at the end of the vertices giving a point for each collected data point (Figure 13).

 

Figure 12

Figure 13
Data points generated by Vertices to Points tool

 

These are only location points however we are interested in displaying the attributes we collected for each point as well. In order to this a simple join between these surveyed points and the original Excel sheet with the attribute information in it. The join is based on the ID fields. Once these are joined we were able to display not only the locations but the attributes we collected as well. Figures 14 and 15 show the collected data points sorted by color and car brand respectively.

 

Figure 14
Map showing data points by vehicle color

Figure 15
Map showing data points by vehicle brand

 

Results and Discussion

For the most part our data points seem to be quite accurate and line up with the real life aerial imagery very well. There is a row of cars that seems to be slightly off the actual arrangement of the cars in the parking lot but this could be due to old aerial imagery that has different parking spaces than the current layout of the parking lot. This also could have been user error causing inaccurate distance readings with the TruPulse unit. It also could have been incorrect entry of the distance values but this seems less likely because there seems to be a pattern to the location error. If it was incorrect data entry you would expect a point that is drastically our of place and random. Making sure the base location does not change during data collection is vital. Movement from the base point between point collection will give you inaccurate readings. Like I talked about before other errors could be caused by shadows or sun reflecting off car windows which make it harder for the TruPulse to get an accurate reading.

Data collection went very smoothly for our group. We were familiar with the technology and technique we were to use and weren't really doing trial and error to find the best way to collect the data. This cut down on the time it took to collect our data and I think it also improved our data accuracy over someone who has never used this technology or method before. From reading past years blogs we could see what worked well and what didn't. From that information we made the biggest decision of where to put our base points for collection. The key to this exercise for us was the fact that our base points were elevated location that had few if any obstacles between us and the data point locations. We were able to collect our data in just over an hour which was pretty fast for the amount of points needed. If you were going to be out in the field for extended periods of time extra batteries or potable chargers for the tablet and TruPulse would be good to have. Anything you can do to cut down on the risk of technology failure is ideal.

Once we had our data collected the analysis and map creation for this exercise were fairly easy. It took about 20 minutes to run our tools in ArcMap and get the data in a displayable format. We only did 2 attributes for our points but the detail you could collect and display for each point is endless. It all depends what the purpose of the project is.

 

Conclusion

This is a low tech method of data collection. It is handy to know how to use because we all know technology fails from time to time. (Usually when we need it most.) This activity could have been done with a measuring stick and a compass, you don't need anything fancy. We were lucky using the TruPulse instead but it can be done in many other even simpler ways. The class leaned a valuable field skill that is applicable in many situations but more than that we learned the best way to do this technique and what to watch for that could reduce accuracy of your data.