Field Navigation: GPS

Introduction:

In continuation with the past two week’s activities (creating a map of the navigation area and navigating using a map and compass), our task this week was to navigate the Priory in Eau Claire using only a GPS unit. The main objective of this activity was to analyze the efficiency of using a GPS unit to find points. We were also interested in comparing the efficiency of the GPS unit to the efficiency of a map and compass (distance and azimuth) to find points as we did last week. Each technique has its benefits and drawbacks. The GPS is easier to understand, but our navigation was less direct than with the map and compass. The GPS functions were not entirely accurate either—the compass in particular was unreliable.

For this activity, we were working with the same groups of three students and within the same area in the Priory as last week. However, we were given a different course than we had last week with six different navigation points to find. There was a total of six groups of three students. Two groups were assigned to each course of navigation points working in opposite directions.

Each person was provided with their own GPS unit, an etrex Legend H by Garmin (Figure 1), and coordinates of the points in UTM and latitude/longitude. We were able to find the points by comparing the given coordinates and the coordinates on our GPS units. Each group of three worked together to find their assigned points despite the fact that every individual had their own materials. We used the track log function of the GPS units to record our positions in the field (further details in the Methods section) to see how directly we traversed between points as well.

Figure 1: This is the Etrex Legend H GPS unit by Garmin that we used to do our GPS navigation for this week.

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Methods:

Before we were able to begin finding our points, we had to set up the track log function on our GPS units. The track log records the location of the GPS at a fixed time interval. For this activity, the units were recording our locations every few seconds. The time interval varied slightly between units, however, because we did not establish a decided interval before navigating. The track log was very simple to set up—we turned it on when we wanted the unit to begin recording and turned it off when we were done. It was important to make sure we turned the track log off after we finished our navigation because we would have far too many irrelevant points otherwise. We also had to make sure we had enough battery life for our GPS units before setting off.

Once we started the tracklog, we began searching for our points. With only the GPS to guide us, we were very limited. The GPS could provide the coordinates of our current location and a compass. However, the compass was extremely inaccurate and could not be relied upon.  We had our coordinates set in UTM and could orient ourselves by comparing the coordinates of the points to the coordinates on the unit (Figure 2). Knowing that our origin in the UTM coordinate system was to the southwest of our study area, we determined that the higher the X coordinates went, the further east we were traveling and the higher the Y coordinates went, the further north we were traveling. We had to test which direction we were traveling simply by walking in a certain direction and seeing if the coordinates were getting higher or lower. We would navigate to each point by comparing the coordinate values from one point to the next. For example, if Point 2 had a higher X coordinate value and lower Y coordinate value than Point 1, we would walk southwest by going in the direction that would give us higher X values and lower Y values according to the GPS. This was simple conceptually, but it proved to be tricky in the field. We eventually decided to get as close to the Y coordinate value of the point as possible first, and then try to match the X coordinates.

Figure 2: This is the data, given to us by our professor, that we used to find the  points for Course 3. We matched the GPS coordinates to the coordinates in this table to locate the points.

The next step was to load the track log points and save them as a shapefile. I connected my GPS unit to a computer using a USB cord and loaded the data into a program called DNR GPS. The program was relatively intuitive. It was important to remember to save the data in the correct coordinate system and as a point shapefile rather than a line which was the default. After saving the data as a shapefile, I created three maps of the track log data using ArcMap—one for my track log points, one for my group, and one for the entire class.

Figure 3: This is the map of my track log data. As can be seen, I was not traveling directly from point to point.

Figure 4: This is a map that includes the three track logs from my group. The track logs follow a similar route but are not exactly the same.

Figure 5: This is a map of the class track log data. It is sorted by the different courses and shows that there were many different paths taken to get to the same points.

Results:

In comparison with last week’s navigation exercise, using the GPS seemed to be much more difficult than using the map and compass. Without a map and properly working compass, it was hard to orient ourselves, and we found ourselves looping around our own tracks—those woods began to feel like the twilight zone after a while (Figure 6). As seen in Figure 5, there was a lot of variation between groups that were navigating the same route because it was hard to keep track of the direction we were traveling. There was variation among the track logs within our group as well, which may be due to problems with the GPS units or slight variation in the paths we were taking (Figure 7). Without the luxury of a map we also were unable to anticipate the type of elevation changes and terrain we would be going through. We found ourselves crossing a rather steep gorge at one point. The upside to the GPS unit is that it can be quick to set up and easy to understand. The track log function is another added benefit to a GPS because it can record exactly where the user is traveling, and the data can be used to create maps.

Figure 6: This is the area that we looped around to get to Point 4. We went around this loop  clockwise meaning that we went way out of our way to get to the point and crossed our own tracks on the way to Point 5.

Figure 7: This is one example of an area that the track logs varied among my group. It is also showing the difference in the time intervals that were used. The yellow track log (mine) had a time interval that was larger than the other two so the points are more spread out.

There we similar challenges between this week and last week in terms of the nature of the field. There was quite a bit of snow cover (Figure 8), though somehow there was even more snow than last week (I remembered my snow pants this week though—score!). The brush was also bothersome. Unfortunately, keeping an eye on the GPS meant that I was not looking out for tree branches and walked into a couple solid branches along the way. We had to navigate around certain features in the field as well, which threw off our navigation as we lost track of the direction we were going.

Figure 8: This is a photo of one of my group members walking through a clear area in the Priory. It  gives a slight idea as to the depth of snow we were walking through.

Conclusion:

This week’s activity consisted of using only a GPS unit to navigate in the field. We learned how to use the track log function on the GPS to record our locations and save the data as a shapefile to be used in ArcMap. Working in groups of three, we navigated to six points in a large wooded area by matching the coordinates on our GPS units to the given coordinates of the points. We found that using a GPS has both benefits and drawbacks while navigating. I thought that the GPS was more difficult to use than the map and compass for navigation because we could not orient ourselves properly and were less aware of our surroundings. We were definitely not travelling directly from point to point as we were with the distance and azimuth technique because of this.

Field Navigation: Distance and Azimuth

Introduction:

The purpose of this week’s activity was to learn how to navigate in the field using traditional methods—distance and azimuth. Azimuth is the angle between magnetic North and a point on the Earth's surface. Using the maps we made last week, a compass, and the coordinates of certain points, we were able to find these specific points in the field. We were given a laminated card to punch at each point so as to prove that we navigated to all of the correct points. The field for this activity was a hilly, wooded, one hundred acre plot known as the Priory in Eau Claire (Figure 1).  Though we ran into several road bumps along the way, my group was able to find these points relatively easily.

Figure 1: This is an aerial photo of the Priory in which we were to find our points.

Methods:

Before we were able to go out into the field, we had to plot our points and learn how to use the compass to find azimuth. We were given six points in a course with their X and Y coordinates (in a UTM coordinate system) to plot on the maps we selected from last week. Unfortunately, the maps we chose to use either did not include a grid system, or the grid system was in the wrong coordinate system. My map was the one that was in the incorrect coordinate system. Though I could swear I had the grid in UTM, it clearly was not, and couldn’t be used for navigation (Figure 2 and Figure 3). We were forced to use an extra map our professor had printed out (which was lucky that he had done so) instead (Figure 4).

Figure 2: This is a portion of my elevation map used for the field navigation. As can be seen with the labels on this grid, the coordinate system is not in UTM like Figure 2. The coordinate system here is unknown.

Figure 3: This is a portion of my elevation navigation map for the Priory that is in the correct coordinate system--UTM. The labels here are correct and can be compared to those in Figure 1.

Figure 4: This is the map we ended up using to do our mapping. It was created by another student and is in the correct coordinate system.

Once we had a suitable map, plotting the points was fairly simple. Our points were on the second course of three created by our professor. Since we had six groups of three people in our class, two groups were assigned to each course. For each course, one group would navigate the points in numerical order, while the second group would go in reverse order. We walked the points in numerical order. Once we knew which points we were assigned and which direction we would be navigating them, we were able to match the UTM coordinates given to us by our professor to the X and Y coordinates on the map (Figure 5). The grid on this map was fifty meters by fifty meters, so we had to do some estimating for the location of the points, but we were fairly confident that the points were in the correct location. Each group member located the points individually and then compared them to the others in order to ensure that the points we plotted were as accurate as possible.

Figure 5: This is a table of the relevant information for each of our navigation points in the Priory. The last point does not have distance or pace information because these were not necessary to find our way back to the main building on the plot.

Next, we learned how to use the compass. The steps to finding the azimuth from one point to the next on our map go as follows:

1. Draw lines from one point to the next on our map. This makes it easier when it comes time to measure the angle and distance.
2. Line up North on the compass with the top of our map. The grid lines we had on the map were not perfectly straight and couldn’t be used as a reference.
3. Line up the black arrow on the compass with the line drawn from point to point (Step 1).
4. Find the correlating angle. If the black arrow is lined up correctly with the line from point to point, and the North on the compass is pointing towards the top of the map, there should be an angle number indicated by a small white line on the compass that is the azimuth from one point to the next.

Figure 6: This is a picture of the compass we used to do our navigation in the Priory. 

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We repeated this process between each of the six points, working from one point to the next in the direction we would be walking, and then from our last point back to home base. We double checked our angles for each point to ensure accuracy as well. Because our magnetic declination (the angle between magnetic north and geographic north from a certain point on Earth) in Eau Claire is practically zero, we did not have to adjust our compasses for this.

The next step was to determine the approximate distance from one point to the next. We used the scale bar included with the map to make tick marks on a blank piece of paper with labels indicating the distance they represented. Then we lined up the marks on the paper with the lines we drew between points to find the distance. We weren’t overly concerned with the accuracy on this, because we knew that if we were following the correct azimuth, we would eventually find the next point. It was just nice to know about how long we would be traveling between points. The distances ranged from about seventy meters to two hundred and seventy-five meters (Figure 5).

We then determined the role of each member. One member would need to use the compass to find the azimuth and direct the other two members (reference Figure 6). This also required several steps to follow:

1. Line up North as labeled on the compass turntable with the black heading arrow.
2.  Hold the compass flat and away from your body or any metal objects as they can throw off the compass needle.
3.  Keep “red in the shed”. This means that the red part of the compass needle should be within the red North arrow on the compass turntable.
4. Find the correct azimuth for the points you are navigating between and direct other members in that direction.

Another member would “scout” ahead in the direction indicated by the member with the compass to a landmark and line up perfectly with the azimuth. Then, the third member would use their pace count and walk towards the second member in a straight line. The pace count was used to approximate our distance in the field. A pace count is the number of steps taken over a specified distance which is usually one hundred meters. We found our pace counts last week outside of the science building. The team member that had the most consistent pace count out of three trials was selected to use their pace count in the field. Kory had the most consistent count--around sixty-five steps per one hundred meters.

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Finally, we were ready to head out into the field. Our professor led us to our first point—a dumpster in the parking lot outside of the main building on the Priory property. From there we went out into the woods to find our points. This went pretty smoothly. Our distances and azimuth values were accurate and we could usually see the points from about twenty meters away. The points were marked with blaze orange flags which stood out very clearly against the snow on the ground. We then punched our laminated sheet to prove that we navigated to our points. Each point had a unique punch so it was clear whether or not we went to the correct points. We followed the same procedure for all points.

Discussion:

As stated previously, our navigation went pretty smoothly once we were out in the field. The most difficult part of being in the field was simply fighting against the snow. We had the great fortune of being out in the field in the beginning of a snow storm (though it truly wasn’t too bad). The area we were navigating was very hilly with a lot of brush and snow cover, so we had to be careful not to slide down any hills or step in any holes. I also whacked my head against quite a few branches along the way and snapped a few branches into the person behind me. We had to look out for bears that are notorious for living in this area as I informed my team member from Milwaukee as well.

The nature of the field posed a bit of a problem for the pace counter, as well. The count was not entirely accurate because the pace counter had to walk over uneven terrain and work around trees. Luckily, we still had fairly accurate counts and didn’t have trouble finding our points. Another problem we had to work around was a large, fenced-off pond of sewage that was in the path between two of our points. Our team did not like the idea of walking all the way around the pond, so we opted for hopping the fence and walking adjacent to the pond, though we had to adjust the pace count slightly. We did this by only counting the steps taken in the direction of the next point, and not those taken perpendicular to the path.

The greatest challenge we had to face, however, was working around the fact that our maps were pretty much useless because they were in the incorrect coordinate system or didn’t have a grid. We would not have been able to find any of our points if there weren’t extra maps to be used. This underlines the importance of ensuring that data is in the correct projection and coordinate system—something that is so easy to overlook while working in ArcMap due to on-the-fly projection. After the navigation was over, I corrected my maps and made sure the grid was in the right coordinate system (Figure 7).

Figure 7: This is the elevation map that I created for the Priory with the correct coordinate system for the grid.

Other than this error, however, I would not change our selected maps. They were clear yet informative. We ended up bringing our maps out into the field for reference along with the map with the plotted points, and they proved to be somewhat helpful. Having the contour lines was perhaps the most useful in finding our location. We could compare areas on the map where the contour lines were bunched together to the steep hills we were walking over. The aerial image was also valuable—in one instance we were able to find our location using landmarks like the freeway and tree line on the map.

Conclusion:

Navigating a field using simple methods is extremely useful for a geographer. As stated in previous activities, one can never fully rely on technology, and a back-up plan should always be lined up in case of any difficulties. As we learned this week, distance and azimuth can be used to navigate a field very accurately. With only a compass and map, my group and I were able to find five different locations over a one hundred acre plot with few complications. The most important lesson I learned from this activity was ensuring that my data is in the correct coordinate system. The activity would have been impossible to complete if we weren’t given an extra map to use because my grid was not in the UTM coordinate system and the points could not have been plotted.

Field Navigation Maps

Introduction:

Our focus for class this week was to create a field navigation map. We will be using this map along with a compass to locate specific points in a wooded area known as the Priory in Eau Claire next week.  Working in groups of three, we each created two maps and later narrowed it down to two maps that we liked best. There are certain challenges that arise while making a map—one of which is balancing the amount of information included so that it has the proper amount of information and doesn’t overcrowd it. Another challenge is finding, choosing, and managing the data to suit the purposes of our project. As we went about making our maps, we encountered these issues and were able to work around them to produce useful navigation maps.

Methods:

Obtaining the data:

In order to save time and allow us to focus on the creation of our maps, we were provided data for the priory in a geodatabase created by our professor. The data included two foot contour lines(Figure 2), five meter contour lines (Figure 1), a DEM, outlines of the mapping area, and aerial photographs of the priory. If we were to find this data on our own, it would have been much more complicated. The aerial images came from a USGS seamless server and the five meter contour lines were derived from the DEM also provided by USGS. The two foot contour lines were taken from a University of Wisconsin-Eau Claire survey of the priory shortly after it was purchased by the university.

Figure 1: This is the line feature for the five meter contour lines. I wanted to compare the five meter contour lines and the two foot contour  lines to show the difference in detail. It was used in my final aerial map.

Figure 2: This is the line feature for the two foot contour lines. It is much more detailed  than the five meter contour line and was used in my final elevation map.

Preparing Data in ArcGIS:

Again, we were fortunately provided with the data already formatted for the most part by our professor. However, if were to obtain the raw data, we would have to take several steps before we could work with it in ArcGIS. Firstly, we would have to make sure the data was in a file format that can be used with ESRI products. If we were to create the two foot contour lines for example, we would have had to extract them from the DEM and save them as a separate line feature. Then, we would need to make sure all of the data is in the projection we wanted. We chose to use UTM as our coordinate system as opposed to a geographic coordinate system so as to reduce distortion for our area of interest, the priory, and have map units that can be measured. UTM is much better suited for large scale projects like the one we are working on. The zone for our area is UTM Zone 15 North.

For the most part, we did not have any issues with the projection of the data as on-the-fly projection in ArcMap corrected the differences in coordinate systems (five meter contour lines were in GCS North American 1983, aerial was in NAD 1983 Wisconsin Transverse Mercator, navigation boundary was in NAD 1983 UTM Zone 15 North). The on-the-fly projection uses the coordinate system of the first feature brought into ArcMap and sets each subsequent feature to the same coordinate system so they may be viewed together. We did run into some problems with the two foot contour lines, however, because they had an undefined coordinate system. Therefore, they were unable to be projected using on-the-fly and would not be displayed with the other data. We were able to resolve the issue by starting a new ArcMap session and adding the two foot contour lines immediately after adding the clipped aerial image. In this case, ArcMap was able to use the on-the-fly projection for the two foot contour lines. The layer coordinate system was set to UTM so that the grid had the correct units and all the layers were in the correct context.

Creating the Map:

Once these steps were taken to prepare the data, we were able to start making our maps. Before deciding on making two maps, I tried to make one map including all of the features I thought pertinent (Figure 3). After seeing the result, an extremely congested map, I created two maps each to be used for a slightly different application. My first map was centered on the aerial photograph of the priory (Figure 4). I added the five meter contour lines so as to have a general idea of elevation and a polygon outlining even more specifically the area that we will be working in. I also included a twenty by twenty meter grid to use as a reference. I had previously chosen a ten meter by ten meter grid, but this was unnecessarily small and crowded up the map.  My second map centered on elevation of the area (Figure 5). I used the DEM and the aerial photo, but set the aerial at a fifty percent transparency so that only major features were visible (Compare Figure 6 and Figure 7). I also added the polygon and grid for this map so as to more easily compare specific points with my first map. Each map also includes a scale bar, north arrow, information on sources, and coordinate system information.

Figure 3: This is a map that includes all of the data given to us from our professor to create a field navigation map of the Priory in Eau Claire. As can be seen, this map is very cluttered and difficult to read.

Figure 4: This is one of my final maps for the field navigation project. It  is based on an aerial photograph of the priory.

Figure 5: This is my other final map for the field navigation project. It is based on elevation data of the priory.

Figure 6: This is the DEM I used to make the elevation map in Figure 5 before I  added the aerial photo. It is difficult to ascertain any sort of position on the map and would still be even if a grid were provided.

Figure 7: This is the DEM with an overlay of the aerial photograph of the priory for the field navigation project. It is much easier to locate a position as compared to the DEM in Figure 6.

Final Selection/Results:

For our final maps, my group and I had to decide which maps would best suit our needs in the field next week. In comparing our maps, we noticed that they were very similar and the selection came down to very fine details because each map included the same features in the same format.. For our aerial map, we chose another group member’s because it was cartographically pleasing (Figure 8).  For the elevation map, we chose the one I created simply because it had the aerial overlay to more easily compare maps (Figure 5).

Figure 8: This is the final aerial map created by my group member Kory Dercks for our field navigation project.

Conclusion:

Through the creation of our maps, we learned that there is quite a bit of work that goes into creating an accurate and efficient map. Collecting data can be complicated as it can come from many different sources and formats. Projecting the data is another very important element in making a map, as we learned after encountering issues with the two foot contour lines. Lastly, it is vital that the map has a sufficient amount of data without overcrowding the map. It must be easy to read while still including all the information necessary for the map reader. We will be testing the two maps our group chose as we navigate the priory next week.