Activity 11:Navigation with a GPS device using a UTM Coordinate System

Introduction

This weeks activity was an addition to the activity last week of orienteering using a compass. In Activity 10 we used a compass to conduct an orienteering exercise out at the Priory which is just south of Eau Claire. This week Dr.Hupy wanted us to use a GPS unit to do a similar activity. He wanted us to see how helpful a GPS could be or how difficult it could be to use the unit because of lack of satellite signal and other issues caused by the elevation changes and heavy vegetation on the property. Dr.Hupy  also thought it would be interesting to have each group create their own orienteering course. He will be using these courses we created in the coming years for compass orienteering exercises. We used our same groups of three people from the previous weeks activity. Each person had a different task just like last week. This time one person was operating the GPS unit, a second was relating the GPS and navigation map and the third person was in charge of using the compass for orienteering and finding easier paths through the woods. Each group created and navigation their new course marking 5 trees with pink tape along the way.,

Study Area

The weather was again perfect for an outdoor activity. It was sunny with an air temperature in the mid to upper 70's and a slight breeze. The pollen content was high because trees and flowers we budding which made my allergies pretty miserable but otherwise it was a perfect day. (see Activity 10 for further study area details). We were in the same general area of the priory property for this activity however the groups spread out quite a bit to create a navigation course on each part of the property and not have them overlap too much if at all. Our course we created ended up being through a lot of very thick brush and brambles.Walking was very difficult even more so than the previous week on the property. Our course was more in the northern part of the property which has a very steep slope down into a much flatter area where our points are located. This was a much more mature forest than other parts of the property. The trees were much larger in diameter than other parts of the property and the tree canopy is pretty thick though this portion of the property which caused some problems for us with our GPS.

Methods

Before we went out we went out into the field for this activity there was some pre-planning and preparation that has to be done. One thing that had to be done was to set up a GPS unit to use in the field. For this activity like many others this semester we used a Trimble Juno GPS unit (Figure 1). This unit allows the user to load a whole map document onto the GPS. This is nice because that gives you a base map for reference as well as the ability to created layers or feature classes to the map while out in the field. We used our GPS unit mostly for keeping track and tracking what direction we were moving in and then collecting points where we taped the trees for our course. Another thing we had to do before going out in the field was to plot points where we would mark trees to create our course (Figure 2). In order to do this we went into an ArcMap document and created a new layer. It was a point file where we could place points wherever we wanted on the map. We tried to space our points about 150 meters apart to make the course a bit challenging. Once we had the layer created all we had to do is deploy the document to the Juno, When we got out in the field we looked at these points on the Juno and the little locator circle on the screen which tells you where you are and when the points we laid out were covered by this locator circle we found a large tree to place our tape and point numbers on for our course. 

Figure 1 is an image a Trimble Juno GPS unit. This is what we used to conduct this activity. This unit gives you the option of loading a whole map document onto it and editing that document right on the GPS.

 Figure 2 is the an image of the map we created with our new course location points on it. We loaded this document onto the Juno unit to aid in navigation to these points.

Before leaving the parking lot at the priory to mark our trees each group picked a part of the property to place there course in so that the courses did not overlap and most of the property had courses created on it. Once the areas were decided we plotted our points on our paper navigation maps just like we did in activity 10 the previous week. From this point on the activity this week was very similar to the one the week before. We used the compass to find our bearing keeping 'red in the shed' and 'following Fred' to find our new locations for a course. Like I said before we used also used our Juno unit to track the direction we were traveling and hep us get close to the points we previously plotted in ArcMap. This activity was also of test of how well the GPS units would do in the deep valleys and heavy canopy cover on the property. For the most part the GPS unit worked pretty (or so I thought) well which surprised me a bit. While in the field creating our course it looked liked the GPS had plenty of satellites and good signal but as I will explain later this wasn't the case. 

The process of places our points in the woods was easy. We got our bearing walked to the point we had on our Juno map and put a piece of pink marking tape around the tree. We then wrote the group number and point number on the tape so Dr.Hupy knew which group made each course and which points were part of each course. We places five points for our course and figures 3-12 are pictures of those locations.

Figure 3  This is the first point marked
 1:1 for group 1 point number 1.

Figure 4 This is the location of the first point.
It is on a rather large tree in a fairly open area.

Figure 5 This is the second point
marked 1:2 for group 1 point 2.

   

Figure 6 This is the location of the second 

point. It is on a medium size tree in another 

pretty open area.

Figure 8 This is the location of third point.
It is on a bigger tree with a large knot on
the side. This tree is in a thicker vegetation
area of the forest.

Figure 7 This is the third points
marked 1:3 for group 1 point 3.

Figure 9 is the fourth point in
 our course.It is labeled 1:4 for
group 1 point 4.

Figure 10 This is the location of the fourth point.
On another medium size tree in an open area where
it is easily visible.

Figure 12 This is the location of the fifth and final
point. It is fairly close to the parking lot and close to a
large clearing, It is on the only large tree in the area.

Figure 11 is the fifth and final point
 in the course. It is marked like the
other  1:5 for group 1 and point 5.

Discussion

As I mentioned before, when we were out in the field placing the markers and recording the GPS location of the 5 points I though the GPS was working well and collecting accurate data. When we got back and I put the collected locations of the new course points into ArcMap they are not accurate at all. There are 3 of the points that are in the general area but the other two points are way way out of place. Figure 13 is the map I created with the collected GPS points which are supposed to be where we marked trees for the navigation map but I would not trust these GPS locations at all. One reason for this awful GPS accuracy is the change in elevations throughout the Priory property as well as the thick vegetation canopy. The e combination of these two factors makes it very difficult for the GPS to record accurate information. The signal from the satellites gets bounced around off of trees and elevation above you causing large error in the collected data. For all of the locations where we collected this makes sense because we were down in a large gully that was at least 20 meters lower in elevation than the upper part of the property. I also mentioned that the area we were walking through had very thick vegetation. There was low ground vegetation just above our heads and another layer of tree top canopy. Both of these vegetation layers cause interference with the GPS readings. Another reason for possible error was that we could not get the GPS to collect points while we had our navigation map open on the unit. To fix this we manually collected the GPS locations for each point by looking at the GPS which gives latitude and longitude all the time for your current location. The lat long was collected in a cell phone memo sheet and later put into an Excel spreadsheet (Figure 14). Once it was in that Excel sheet it was then imported into ArcMap and assigned a coordinate system. This was much more time consuming and frustrating than it would have been if we had been able to just record the locations with the GPS itself and load the locations into ArcMap with a coordinate system and everything all set up.

Figure 13 This is a map of the location that we collected with the GPS of where our navigation course points were supposed to be. Points 2,3 and 4 are fairly close, within 10 meter or so of where they should be however points 1 and especially 5 are way out of place. This could be caused by high interference with the GPS signal or possible human error when we were collecting the points. The green box on the map is around the Priory property so you can see that the points were not even close to that property.

Figure 14 is the Excel table that I created with the Latitude and Longitude of the points we collected. What you see is not lat long but decimal degrees which are used with UTM system. Using an online converter I was able to take the lat long and get the decimal degrees for each point.

This data that we collected in figure 13 will most likely have to be recollected using a different GPS unit. In order to do this we will have to use our orienteering skills previously learned in this class to essentially run our own course we created and find our points. An accurate GPS location will be collected so that Dr.Hupy can actually use this course and know where the points are in the woods on the property. Figure 15 is a map showing the comparison of the plotted points and the GPS locations we collected. These points should be exactly the same or at least very close but they are not even close and that is why the locations need to be recollected.

Figure 15 This is just a map of both sets of points to show how far off our GPS collected points were.

 Conclusion

This activity was good because it made us use multiple skill sets we have learned during the semester. We used our knowledge of a Trimble Juno unit along with ArcMap, our orienteering knowledge from last week as well the process of creating a navigation map again with our plotted course points. Again the pre planning came into play more than other activities this semester and we see again how technology does not always make things easier. Human error and attention to detail were also important to the success of this activity. It appears as though our group may have made some mistakes in data recording but it is also possible that our GPS unit failed us. The only way to know is to take another GPS unit to the location and repeat the collection of the new course points.