Topographic Survey with total station

Introduction:

In the previous entry RTK GPS Unit was utilized to create accurate point collections. In this week we are using the RTK GPS Unit again but with some added surveying equipment. The Topcon Total Station and the Prism Laser collector. This is a useful application that is similar to the previous activity of the Distance/ Azimuth survey methods. The Major difference between the Distance/Azimuth survey and the Total Station survey methods is that this does the same surveying job but much better. This method will be used to survey points by using the total station for later use in building a micro topographic surface with the points that we have collected.

How Total Station works using Geographic Origin.

Methods:

Setting up the Topographic Survey and Total Station

This topographic Survey with total station was a group effort with another partner since one person needs to be in charge of the Prism mechanism and one person needs to enter the points into the RTK GPS Unit. Classmate Luke Prashak was here to assist in the collection of points.

To begin the setup of the RTK, Prism, and Total Station needs to be located and set into a correct designated static position. This position is called the static point or the occupied point. To correctly set up the static position of the total station due north needs to be found. This will then be taken with points that were set up with orange flags. By using the orange flags as backsight points we can now know the exact static point via the prism collection based on collecting the information on the orange flags. Because this system is dependent on mm accuracy we cannot touch the total station once it is set into the static position.

 Prof. Hupy in the field with Total Station and RTK unit 

The first step is to gather the backsights which are BS1, BS2 etc. Once the backsights are collected it is time to gather the occupied point where the Total Station will reside. In order to set up the TSS we have to ensure that the surface is clean and dirt free. After the surface is cleaned, extend all three legs equally and secure the locking mechanism for a sturdy base for the tripod. Once the base is set centered attach the tripod head over the point while remaining level. A good way to ensure centering is to drop a pebble from the center of the tripod head. Then step down firmly on the footpads to set the legs into position.

The instruments are next to set up. Center the tripod head and secure the instrument to the tripod and bring all the leveling screws to the natural position below the line on the screw post. From here look through the optical plummet for parallel and focus on the ground. With the laser plummet on, position the instrument directly over point by using leveling screws. Be sure to observe what two legs need to be adjusted to bring the bubble into the middle and do not move the third leg. Release the horizontal tangent lock and rotate the instrument until tubular level is parallel. Once everything is centered and level it is time to recheck the fine (tubular) bubble vial in position 1 and 2 and adjust as needed. If no adjustments are needed then measurements can begin to be made.

To take points we need to turn on the total station and switch on the Bluetooth which is located in the parameters portion in order for the Tesla to recognize it. Now it is possible to connect the RTK to Total Station. To begin the OCC/BS Set up go to the Home Screen for Magnet and select the Setup icon and then select the backsight icon. Enter all the needed information for the total station and for the Prism Rod. It is very important to keep the prism rod at the same measurements throughout the point capturing. If the rod needs to be moved it will have to be recorded in the Total Station that the prism was moved or it will throw the data collected and will not be nearly as accurate. Finally place the prism rod over the backsight point and gather the point. This is needed to zero out the total station for due North. Collect the GPS points with the Tesla in Magnet Using the total Station and Prism in the Survey icon screen.

Collection of Points with RTK and Total Station
The system is now ready to collect points. Looking through the viewfinder on the total station it is imperative to lock onto the prism system. After locating the prism system on the Total Station it is then possible to use the view finder to manually focus in on the prism. at the ranges we were dealing with the magnifier was not necessarily needed but it was useful to practice. We are then ready to collect the point, Signaling the person manning the RTK will then collect the point after a series of seconds the point is then collected and we can move on to the next adjacent point. The points collected will be used with additional points to later be imported into ArcGis and create a topographic map. 

Creating the map in ArcGis 

By using the data imported from the RTK and Total station in a .txt format it is possible to use the create feature tool from xy table and import the points into ArcMap. From here it is possible to use these points to create a IDW (inverse distance weighted) analysis which would include the z axis. IDW uses every point collected to create a raster that will give the analysis of height. To use this tool  import the xy and z data into the tool and then run the analysis. From this data the height is now mapped in a topographic manner. The lower the point will be green the higher the point will be red. 

Results: 
From the IDW the green points are the lower collected areas that are taken in the little Niagra river area and the higher points are the areas that are collected above the geographic origin point which is where the total station was located. This is an important tool in mapping areas that require height to be accurate to the nearest millimeter. 

collected points interpolated with IDW 

Conclusion: 
By using Total Station and RTK we can map areas with the greatest of accuracy. This is an important tool when using drones is either illegal or ill advised. The IDW tool is useful in creating a topographic map that can be used for analysis in other areas. 

Surveying of Point Features Using Duel Frequency GPS

In order to create a topographic map it is imperative to understand the Dual Frequency GPS equipment.

In order to do this we have to know what a dual frequency receiver does. This is a signal capturing system that can select and simultaneously receive signals on two frequency channels during a specific time period. This is a good system to use to gathering point data that is incredibly accurate and can accurately gather points to within a centimeter of where they were taken. In this introductory lesson we learned how to take different points and then use the data to create a map in ArcGIS.

 RTK Unit 

The study area that we have selected was the area that is outside of Davies and UWEC Phillips Science Hall. This area allowed us to collect numerous different points such as trees, garbage cans, and light polls. This was useful as an introductory course in the Surveying. The surveying equipment utilized is the RTK GPS Unit. RTK stands for Real Time Kinematic. It is used for extremely high accurate positional accuracy by using a consistent connection to the internet via Wi-Fi. Every time we collect a point using the RTK GPS Unit it collects 30 points and averages all of them out. This allows for extremely accurate data collection.

RTK Unit Screen 

When collected there is also XYZ data from the GPS unit. This can then be used in ArcGIS by selecting the tool import XY and map out the points in ArcGIS. The points can then be redone in ArcMap by selecting the projection which is UTM zone 16. The XYZ data can then be used to map where the points will be located. From here it was simply selecting the points in the attribute table by what they were in the definition which was entered into the GPS unit upon capture. From here it is simple to use this data to create a basic survey map.

The results of this data show very accurate GPS collected points using the RTK GPS Unit. This is a useful tool for surveying points that require accurate information. An example of this would be road surveying and forestry work. The results of the captured points are incredibly accurate. This RTK GPS Unit also has the added benefit of allowing us to input attribute data directly on capture versus where it would be necessary to know what to capture before surveying with other equipment.  

Collected Survey Points 

To conclude the RTK is a useful tool when accuracy is important to the application at hand. The only downside is that this a large unit and is slightly cumbersome to carry around everywhere. The GPS unit is also great since it allows on the fly attribute creation. Overall this is a very useful tool that I look forward to working with in the future. 

Distance and Azimuth Surverying

Conducting a distance Azimuth survey

Introduction: surveying with a grid based coordinate system is good on small plots but it is not ideal for many geographic circumstances. These days you can use GPS technology along with survey stations but sometimes you cannot rely on technology to come through. This is why distance and azimuth can come into play. It is a very basic technique that can work on many different conditions that can rely on sampling techniques and point quarter method. This allows us to map out linear features on a landscape from a singular point based on the azimuth of where the point was taken using the tools in ArcGIS such bearing distance to line command and feature vertices to points command. In this exercise we looked at the tree density in Putnam Park.

Azimuth Surveying in quadrants from Origin

Study Area:

The area of study for this assignment is the Putnam park area of the University of Eau Claire. In this area are new and old trees that have been planted on the grounds of the University of Eau Claire. This area is a good step for Azimuth surveying as it allows for a variety of tree species to be mapped with differing diversity and density. We will be collecting 10-20 point-quarter data collection of these locations from a centralized location that will not change.

Survey Area: Putnam Park 

Methods:

The first step in Azimuth surveying is to do the research of azimuth surveying. Azimuth surveying is an angular measurement in a spherical coordinate system that looks at the vector from an origin point which is then projected onto a reference plane. The angle between the projected vector and the reference vector is called the azimuth. An example is the North Star. The origin point can be the person looking at the point and the azimuth would be the angle between the North Star, the surface of the ground and the perpendicular projection of the ground. This can then be measured in degrees and can then be used in mapping. This is an older style of mapping without the use of relying on technology.

 Although we still rely on the technology in the form of the True Pulse 360 B.

Once we have the 360 B true pulse set up in an origin point in Putnam Park it is time to begin to take points. We are looking at trees and the azimuth of the trees as well as the distance from the point. To collect the distance we will be using a laser pathfinder and will relay the information back to the True Pulse system. This will allow use to laser designate the distance between the origin point and the point that we are collecting, this means we only have to use one latitude and longitude point which will be the origin station.

True Pulse 360 B 

After the points are collected it is time to import the data into an excel spreadsheet. The XY will be the same for all the points right now. When we enter the excel table we are adding in the diameter the azimuth, distance and tree type. From here we connect the excel table to the blank map in arcgis.

We will then convert the excel table to a usable format in arc catalog by adding the data into a geodatabase which we can then use the xy table from the excel sheet and create a point based on the xy data. It is important to mark the xy table correctly otherwise the next tools will not work. When the data was imported into excel the xy data was flipped so the Y coordinates were actually the X coordinates and the X coordinates were the Y coordinates. This meant that the data could not be used until it was corrected.

XY Data

Once this data is converted into a single point we can then run the tool bearing distance to Line command in the features tool set which creates a new feature class containing the geodetic line features constructed based on the values in a xy coordinate field as well as the distance field of the table. This will create only lines from the origin point. It is important to note that since this is a broad service WGS 1984 coordinate system needs to be utilized to make accurate readings.

Since the Bearing Distance to Line Command only creates lines from the origin point we will have to use the Feature Vertices to Points command in the features tool set to create actual points at the end of the lines. This will allow us to use the data that we collected by creating a feature class generated from the vertices of the lines. In essence it will create point data at the end of our line data.

Results:

The results of using Azimuth surveying are extremely accurate. This is a useful tool that is still in use today. It allows highly accurate data to be accumulated and does not rely on GPS or other highly advanced technology. This means that because the technology is not present it has a higher risk of not failing. The results from this azimuth survey are impressive and show that from a single origin point we can collect data that can be used for a multitude of purposes including road surveys, tree surveying and logging expeditions.

Conclusions:

Because technology can sometimes be a hindrance in field work it is important to rely on older more trusted methods like Azimuth surveying. If data needs to be collected in heavy foliage which would normally interfere with GPS systems Azimuth surveying could be used instead to create accurate maps. This is why Azimuth mapping is still used heavily for surveying work such as road construction and tree surveying.