Field Navigation Part Three

Use of handheld GPS units for field navigation.

Introduction:

Over the last two weeks our group, Andrew Peterson, Amy Bartel and I have completed two separate exercises associated with land navigation; those exercises included the use of available data and resources to create a navigation map, and using that map to do traditional land navigation using the map and a compass. The navigation exercise was done at the Priory and the immediate surrounding area. The Priory is located approximately 5 kilometers south of the University of Wisconsin Eau Claire (UWEC) campus on Priory Road. Directions to the Priory from UWEC are as follows. From the main campus area take Roosevelt Avenue east to State Street, turn right on State Street and follow it south until you come to Lowes Creek Road, turn right on West Lowes Creek Road, you will cross over Interstate 94 then come to Priory Road, turn right on Priory Road and watch for the sign for the Priory on your right. For this week’s exercise we used modern technology (handheld GPS units) to navigate another portion of the area surrounding the Priory locating several points along the way.

Methods:

For this week we were not allowed to use a map to aid in our navigation. We were restricted to the use of handheld GPS units and given the coordinates of the points we were to locate (figure 1). The point locations were given in UTM NAD 83 coordinates. Our GPS units were also set at UTM. Again, there were three courses, each consisting of six points, to navigate and six teams navigating. One team on each course navigated the course forward (1,2,3) while the other team navigated the course in the reverse order (6,5,4).  Our group was to navigate the second course in the reverse order.

Fig.1. During this exercise we used a handheld GPS unit to
navigate to several points on one of three courses set up at
the  Priory, in Eau Claire, WI.

We began by starting a track log on the GPS to record our movements throughout the exercise. In order to locate a point we first checked the point coordinates of the point we wanted to navigate to, then we observed our coordinates on the GPS unit. Now the tricky part, we first had to get ourselves moving in the correct direction. In order to figure this out we had to ‘wander around’ a bit and figure out which way was which and get our bearings in relation to the point we wanted to navigate to. After we had a general idea of which direction we wanted to travel in we began to walk in that general direction, while walking we had to continue to watch our location on the GPS to be sure that we continued in the correct direction, adjusting our travel according to the easting and northing on the GPS (figure 2).  After we located a point we would repeat this process for each consecutive point until we finished the six point course. At the conclusion of the course we stopped the track log.

Fig.2. While navigating the course we had to
 maintain constant interaction with our GPS units in order to keep our bearings. 

After the exercise we downloaded our track logs using DNR Garmin software. We connected the units to a computer using the USB cable supplied then opened the Garmin program. We clicked on track and download. After the data were downloaded we went to file and save to our file as a shape file. Then in Arccatalog we import the shapefile to our geodatabase as a feature class and projected it in UTM, which we also saved into the Priory geodatabase for use by other students for their mapping. I added the locations of all of the points around the Priory to my existing map and then added my tracklog and created a map representing myself (figure 3). I then added the tracklogs of my teammates to the map and created a map of our combined efforts to locate our six points (figure 4). I gave each team member an individual color and shape to distinguish one from another.  Finally, I added all the available track logs from my classmates to the map in group layers. Each group was given a unique color and each member of the group was given one of three symbols, these same symbols were used for all groups. Then I finished with a map of the class’s efforts during this exercise.    

Fig.3. Map of the Priory with Stacy Camren's track log. There was a lot
of 'wandering' during this exercise. 

Fig.4. Map of the Priory with all of the track logs from the members
of my group. Note two track together and one separate from the
others, one member was late and had to navigate the course without
 the other two members.

Fig.5. Map of the Priory with all available track logs from the class.
There is at least one track (black) that does not seem to fit any of the
 courses, it was also not clearly identified in the geodatabase as to who's
track it was. 

Discussion:

There were several challenges this week; the first was getting our entire team together. One member of the team was late and we were forced to begin without them. Because of this we did not actually see the other member of our team until we were finished. The second challenge worth mentioning is both the new snow and the amount of snow present. The new snow was clinging to the trees very heavily and in some instances may have reduced the effectiveness of our GPS units by blocking or reducing satellite reception (figure 6). The amount of snow present made it incredibly difficult to walk in areas where there was a combination of a steep slope and snow cover that was more than knee deep (figure 7).

Fig.6. There was several inches of new snow , much of it
was still clinging to the tree branches and may have reduced
the accuracy of the GPS units.

Fig.7. Much of the area was covered with snow that was knee
deep and deeper making it very difficult to travel in.

The last of the large challenges was using the GPS to locate the UTM point coordinates. While navigating from point to point you naturally do not walk in a straight line. This can be cause by many things such as one leg being slightly longer or stronger than the other, or even the Coriolis Effect. But much of our deviation over these short distances was caused simply by obstructions such as trees, brush or in one instance a fence that had to be navigated around (figure 8). The difficulty was every time we made a directional change, either on purpose or not, we had to figure out what our bearing to our point should be again. This resulted in very inefficient direction of travel and a lot of misdirection; however, we did not have to be as precise when navigating around obstacles.

Fig.8. There were some areas that you are
forced to navigate around due to trees and
brush.

Overall we finished the course much faster than we did with traditional methods. Traditional methods used much more time to prepare and required more cooperation between individuals, however if done well traditional methods were much more direct.    

Conclusion:

It appears to me that each of these methods may have an appropriate use depending on time and manpower. Between these two I would choose to use traditional land navigation because of its simplicity and directness and the fact that I am comfortable with this method. If possible it would make sense to use both technologies simultaneously. It also would have made a difference to insert the navigation points as waypoints and navigate directly to them.