Orienteering Exercise

This week’s class focused on using the compass skills we learned a few weeks ago in a real world setting. The location is the Priory on the south side of Eau Claire, WI just south of Interstate-94. The area is mostly wooded and is now the present site of a dormitory and the UWEC children’s center. There were maps made in an earlier blog which show the location and include a detailed account of the study area. 

Orienteering is defined as “a sport in which people use a map and a compass to travel along a route they do not know as quickly as possible” – MW dictionary. For this exercise we were given a compass, two maps with grids both in meters and degrees, and a list of checkpoints with coordinates in decimal degrees and meters. There were a few steps included in the orienteering exercise. 1, plot the coordinates on a map. 2, head to starting point and figure out azimuth and distance to first point. 3, send a “runner” ahead to a specified point. 4, a pace counter will count their steps as they head to where the runner is. This is to help estimate how much further the checkpoint is. 5, once the team arrives at a checkpoint repeat steps 1-4 for the next one.

 

Figure 1. Our pace counter on his way to where the runner was. Avoiding brush as the pace counter was difficult because it meant that his count may be inaccurate. The pace counter needed to be able to count only steps which reached the runner on a bee-line.

Figure 2. Calculating the distance traveled from the last point and the azimuth to the next point.

My group was given a list of five checkpoints to reach and an issue we ran into right away with plotting the points was that the grid for the map in degrees used seconds and minutes whereas the coordinates given were in decimal degrees so one of the group members spent extra time to convert the decimal degrees and compared his points to the points on the map in meters and found they were very similar. 

Figure 3. A map showing the location of the checkpoints with lines drawn to show the direction to each point.

Once the maps were filled with the checkpoints we started the exercise. From the starting point one member found the azimuth, my job as runner was to run ahead and help clear a path. Then the pace counter followed. The first point was easy to navigate to but we quickly learned that this exercise was not going to be fun.

Figure 4. The location of the second checkpoint was at the bottom of a ravine located under fallen brush and logs. Getting in and out of this ravine was a tremendous ordeal and not something fun.

The underbrush in the forested area was a lot thicker than I had anticipated. Luckily I wore jeans and appropriate shoes to keep my legs free of scrapes and scratches from all of the barbed bushes. Climbing out of the ravine from point two I started to slip so I reached to grab something, not looking, and grabbed a branch of something that was filled with barbs many of which broke off and stuck in my hand. A day after the exercise I found a barb still stuck in my thumb so I’m sure there are a few more barbs on me somewhere. 

We have been with the same group for almost every exercise this semester and building up our trust in one-another throughout the semester was vital to this exercise as it would have been easy to get frustrated in these conditions. The temperature wasn’t a factor as it was a nice 70 degree day but it felt worse as we began to get sweaty from walking about a mile over the rough terrain of the Priory.

Figure 5. A much smaller ravine than at point two. In the background you can see someone in a green shirt for reference of how large this ravine is. Even though this ravine was easier to cross than the last one it still helped to make the course more challenging as we were on our way to the third point.

The next time we do this exercise it would be beneficial to have a map with labeled contours instead of just contours. Since the points came with an elevation we could have estimated our height to see if we were closer or further from a point. A shirt with long sleeves and light gloves would help out with preventing cuts and scrapes. One of my friends decided to cut his jeans into shorts right before starting the course which turned out to be a major mistake for him as his legs we severely cut up by the end.

Microtopography Survey

Introduction

This week’s assignment was another surveying mission. The TopCon total Station was employed to collect elevation data for the University of Wisconsin – Eau Claire’s Campus Mall. The Total Station is a surveying tool (figure 1) which is commonly used by surveyors because of how accurate the results are (sub-meter). The Total station records in meters a northing, easting, and height. It works by shooting a laser to a prism which is held on a pole with a fixed height and by determining the angle and time it takes to travel to the prism and back it records the values.

Figure 1. The TopCon Total Station set up and ready to record survey points. The GPS unit on the front is connected via Bluetooth to the Total Station so as the total station records it is being sent to the GPS unit and plotted on a virtual map.

 We worked in a group of four to survey the campus mall which is a newly constructed green space which is along Niagara Creek. The mall is in the shape of a miniature amphitheater built with a gentle slope then once it reaches past a sidewalk it forms a steep decline to the creek.

Figure 2. UWEC's campus mall viewed from the West. From this angle you can see the gentle slope from northwest to southeast forming the amphitheater shape.

Methods

Data Collection

A total of 108 points were collected over the course of two hours. Weather conditions were chilly but tolerable. In our group of four we used a rotation which allowed everyone to gain experience using the Total Station to collect data. An occupied point was established before any data was collected. An occupied point is the position from which all other points will be measured (similar to the azimuth assignment). Data collection first used a circular patter following the sidewalks around the campus mall but then changed to a side to side method. The 108 points collected can be viewed in figure 3 below.

Figure 3. A map showing the location of all 108 points recorded and a special symbol showing where the Total Station was positioned during the survey.

Results

The kriging method was used to create a digital elevation model (DEM) from the points. Below in figure 4 is the DEM of the campus mall.

Figure 4. A DEM created using the kriging interpolation method. Notice how the slope on the mall appears to have a sharp break running almost perfectly along the NW-SE line.

Since the model has an elevation associated with it the DEM can viewed in 3D in ArcScene. ArcScene is able to create 3D models from any data set with any kind of value such as elevation or demographic info per county, block group, state, etc. A 3D model with a view from the south of the campus mall was created and includes a figure to show where the occupied point was located (figure 5)

Figure 5. The DEM displayed in ArcScene with the aerial image overlaid and clipped to the size of the DEM. This image is of the mall when viewed from the south.

 

Discussion

The goal of this lab was to familiarize ourselves with the TopCon Total Station and to learn a new form of surveying. Throughout the survey the group discussed how to better collect points and where to collect more data to capture the micro-topography. Since we switched how we were collecting data it was difficult to decipher where we needed more data collected so once we reached 100 points we collected a few more along the stream to help increase the size of the study area.

One major issue we ran into while processing the data was that once in ArcMap all of our points minus the occupied point were 180 degrees off. To correct this error we started an editing session and selected all of the point. Then we chose the rotate tool in the editor toolbar and set the occupied point as the anchor point then rotated all of the points by 180 degrees around the occupied point. This completely corrected the error then we were able to go ahead and create the DEM.

Another issue was that all of the points appeared to be over a meter north of where they were actually taken. This error could be due to numerous factors but most likely because of how the occupied point was measured with a GPS which was not up to par with the rest of the Total Station.

Conclusion

If given more time, a more thorough survey would be conducted and the points would be included with the previous survey. The error discovered while processing data was because we used the back sight instead of the front sight when setting up the Total Station. The back sight should have only been used if we were to have moved the Total Station but because there was no interference we did not need to move it. The DEM created shows the gentle slope on the campus mall and where points were taken closer together it is more accurate. The TopCon Total Station is a magnificent tool and it is no wonder why it is used in road surveys by engineers.