Activity 6 Navigation: Priory Navigation

Introduction

This week's lab is a continuation of last week's development of navigational maps exercise. For this lab, the class was split in groups of 3 and used the maps created from last week's lab to navigate through the Priory in Eau Claire, Wisconsin. Our objective was to find 5 locations previously marked by the professor and other classes with pink ribbons labeled with a site number. To do so, we were limited to our maps and a standard compass equipped with a ruler, only using a GPS (Fig.2) to log our trail for later evaluation and in cases where no marked location could be found (as the locations were marked in previous years, ribbons may have fallen off or blown away by the wind). The intention of this lab was to help us gain experience using basic navigational tools for situations in which either newer technology fails or is inaccessible. We also used this lab to evaluate the effectiveness of our maps created from the previous lab.

Fig. 1: Standard compass (left) equipped with ruler on the edge to plan our routes and
navigate and a GPS unit (right) to log our track.

Methods

The first step was to mark on our maps the coordinates of the five locations given to us by the professor (Fig. 3). We then compared our mapped locations with each group members' locations to assure we correctly marked each location. We then chose a starting point from which to navigate to our first location. We chose to start from a tree near the access of the parking lot closest to the forested area of the priory as this was an easily found location on the map and we could correctly determine the distance and direction we would need to travel to find our first marked location.

Fig. 3: Mapping coordinates of our 5 locations and determining routes.

After mapping our locations and determining a starting point from which to navigate to our locations, we had to plan our routes to each of the 5 locations. This was done by using the compass edge to draw straight lines between each point location on the map and measuring the length of that route and convert it from centimeters to meters using the scale on the map (1 cm: 35 m) (Fig. 4). The pace count was determined as we navigated from point to point as the person counting paces and keeping direction using the compass switched periodically throughout the lab. This was important to determine pace count between locations on the fly as opposed to at the beginning of the lab as each person has a different pace count. For instance, I walked 67 steps per 100 meters while another groupmate, Katie, walked 65 steps per 100 meters.

Fig. 5: Scott connecting each point location and measuring route length to plan our routes.

Next, we began navigating through the forest to our 5 locations. We used our UTM map as opposed to our Decimal Degrees map as it was easier and more accurate to calculate our distances in meters and pace count conversions using UTM. It is important to note here that each group member played a different role during the navigation portion of this exercise. One person would count paces holding the compass close to their body to make sure they were walking in the correct direction while keeping track of the distance traveled. Another person would stay behind and make sure the person navigating would be traveling in the correct direction as sometimes if the person must avoid brush or trees, they can skew their angle of direction. The last person would either walk with the navigator keeping count of paces and assure direction or remove brush in the path ahead. Normally the third person would be holding the compass and walking with the person counting paces, however, we thought it was easier for the person counting paces to be looking at the compass themselves and for another person to help clear the path as the terrain was fairly rugged and we wanted to limit the amount of error coming from pace changes due to obstacles en route.

Our route to point one was calculated to be approximately 280 meters in length as the line drawn on the map from our starting point to point 1 was 8cm (8cm * 35m/1cm=280m). I was the first to count paces and navigate, so we used my pace count (67 steps/meter) to calculate the amount of paces it would take to reach 280 meters and determined it would take approximately 188steps (280m * 67/100m= 187.6m). After the bearing was set in the correct direction towards the first location, I started navigating towards the first point with the compass held to my chest and counting paces while my groupmates made sure I was heading in the same direction as I had started heading and clearing the path in front of me as best they could (Fig. 6). We followed this same method for locating the remaining 4 locations, but switching roles periodically.

Fig. 6: Navigating to the first location with Katie in front clearing the brush, myself counting paces and keeping an eye on the compass, and Scott making sure we did not alter our direction unknowingly.

Some routes between locations were across steep ravines. In these instances, we estimated approximately how much the slope would change our pace count by looking at the distance between our feet upon taking a first step on the slope and comparing it to the distance between our feet on a normal step in a flatter terrain.

In instances where trees both upright and fallen were creating obstacles in the direction we needed to travel, we would stop to visualize a path that was the most straight-lined possible and chose an easily recognizable feature in the line of bearing to assure we were staying true to the bearing and to help eliminate some pace count error while avoiding obstacles.

Results

We were able to successfully locate only 3 of our 5 marked locations and not all were found right away. For the first location, after walking the correct amount of paces in what thought to have been the correct direction, the marker was no where to be found. Katie had wondered ahead to find the marker while Scott and I stayed back to keep our current position so as to not get lost. Katie had found a marker. However, we figured, looking at the map contour lines, that this was not the correct marker we were searching for. We consulted the GPS unit and found we were headed in the correct direction, but we had not traveled enough steps in the direction to reach the correct marked location. We continued on to find another marker. From here, we calculated the amount of paces to the next location with Scott as the navigator and pace counter. However, upon arrival of the next location, we figured this was actually our location 1 marker as opposed to our location 2 marker. Because these locations were in a similar bearing from the origin location, we must not have traveled far enough still to get to our location 1 marker. From here, we readjusted our bearing and used the same pace calculations to reach our location 2 marker.

Upon reaching the supposed location of our second marker, it was no where to be seen either. We again consulted the GPS unit to discover our pace count was correct despite the steep ravines that were traversed in the process, but we had traveled slightly more to the west than was needed. We headed toward the correct direction, but was still unable to locate the marker until we used the GPS unit entirely as opposed to following the compass to find the marker.

Our 3rd location marker was found with little difficulty, having the correct distance in paces, but were only minimally off from the bearing. Our fourth marker was never found, however, we found a tree in the exact location the marker should have been--using the GPS to verify. This must mean that we had found the location without trouble, but the marker had disappeared. For location marker 5, we experienced the same problem--finding the location it was supposed to be in, but having no marker. From here, we navigated back to our origin point successfully. 

Discussion

After navigating to our designated locations, I felt the maps we used required adjusting. Though ornamental, the imagery basemap did not aid in helping our navigation through the wooded regions and was less important than I had originally assumed. Though it was help in finding an origin point from which to start the navigation process to each of our marked locations. However, our contour lines, which we relied on the most, could stand to be of higher precision as a big problem we faced was the accuracy of our pace counting over steep terrain. This could have also helped us locate the first and second marked locations as we should have been able to tell by the slopes of the terrain where we were in relation to the marked locations. 

Conclusion

This lab allowed us to practice useful navigation techniques using more traditional pace counting and compass methods and operation of GPS in the field. The more traditional methods of pace counting and compass reading can be used in situations where a GPS can not receive a signal. One thing to always consider when navigating using this technique is to always adjust estimated pace count distances according to the slope of the terrain and the amount of obstacles in your straight path. Using landmarks such as distinct trees and rocks is useful in maintaining a straight course. It is always useful to make sure prior planning is also done correctly and in a detailed manner. If you are selecting or creating your own map to navigate a study area, make sure the information and the type of projection is suitable for our study area.