Assignment 7: Navigation with GPS

Exercise conducted on: March 11th, 2013.

Introduction

Again, we were at the Priory for our field exercise. And again, the weather decided to dump even more snow on us the day before and of our field navigation. Whereas last week we navigated the course with a map and compass, this time we navigated only with a GPS unit. We also rotated courses, so that no group did the same course a second time, as they would already have a general idea of where the points were. Armed with a Garmin GPS, we were to navigate the course while recording a track log, which we would upload once back in the lab. Once we uploaded the data, we were required to create three maps: One with only our track log, one with the track logs of our whole team, and one with everyone’s track log.


Methods

Upon arriving at the Priory we were issued our Garmin GPS units and our course number (Fig. 1). While waiting for our final group member to arrive, we were given a short introduction on how to use the Garmin eTrex GPS unit. After about five to ten minutes of waiting we were instructed to start our endeavor, and our final group member would have to catch up with us. We went to our starting point and began to figure out how the UTM coordinates changed as we moved around the area.

Figure 1: Garmin eTrex GPS unit we used to conduct our exercise.

As mentioned in a prior blog entry, a Universal Transverse Mercator (UTM) zone is a 6 degree longitudinal section of the Earth with a meridian down the center (there are a total of 60 UTM zones). For example, our mapping area is in UTM zone 15N, which has a longitudinal range of 90-96 degrees West, with the meridian being at 93 degrees. The N refers to being north of the equator (S indicates south). To remove negative values, a false easting is applied.

So, as we walked around we noticed that when heading north, the northing increased, and when heading east, the easting increased. Since the two numbers were not labeled on the GPS, it was easy to forget which number was which. For this reason, we decided it would be easiest to match one number first, and then match the second. This resulted in us walking slightly greater distances since we wouldn't be walking straight towards the target location.

After figuring out our GPS, it was time to head to our first point. Moving down the hill was interesting with the amount of snow and the way it accumulates on the hillside. With every step down we would be up to our knees or higher in snow. This made the pace slow quite slow, and it didn't take long to become tired and out of breath.

A few steps after we found our first point, Beatriz and I heard people coming down the hill behind us, following our tracks, so we stopped and waited to see who it was. It turned out to be our missing group member, Joel, who was late due to the original vehicle they were going to drive to the Priory being stuck in their driveway due to the snow. With him was Drew Peterson, who realized when they found us that his group was going on the same course, but going in the opposite direction. So, rather than run and try to catch up to a group 20 minutes ahead, he decided to stick with us.

Figure 2: Drew in snow up to his knees. This is what we had to walk through
for the vast majority of the exercise. The only respites from this depth of snow were
paths of other students and a road that is on part of the Priory.

Figure 3: This is an image of me monitoring our UTM coordinates as we navigate
from one point to another. As can be seen, I too have been in snow
up to my knees. 

After we found our second point and were taking a short break, Joel started playing with his GPS and noticed that he could set waypoints. He set a waypoint for our third point and found out that it would draw a line to that point and give the distance and direction to the point. This provided for a more efficient mode of travel, and didn’t require us to pay as close attention to our GPS unit. We decided to use this for the remainder of the time since we all understood how to use the UTM coordinates for navigation, and we would conserve time and energy.

Figure 4: Beatriz taking a short break and comparing the UTM coordinates of her GPS with mine.
We found that despite only standing about 1 meter apart, our GPS differed by 10m
in northing and 6m in easting. 

Figure 5: Joel entering our next waypoint. 
This made our travel substantially more efficient. 

After locating all of our points, it was time to head back and upload our GPS data to ArcMap and create maps of our travel. To upload the data I had to connect the GPS unit to the computer via USB, and then extract the data using DNR software. From there I was able to export the points as a point shapefile. I then created a file geodatabase in ArcCatalog so I would be able to use ArcMap to export the shapefile data as a feature class. Once completed, I then projected the points, which were in WGS 1984, to NAD83 UTM Zone 15N. We then emailed our file locations to our professor so he could import every students feature class into a dataset. When all of the students finished this part, we were able to begin creating the maps. The first map is only the track log from my GPS. The second map contains the track logs of everyone in my group (Beatriz, Joel, and myself), and the final map includes the track logs of everyone in the class.

Figure 6: This is the track log of my GPS, showing my path of travel through Course 2. My path
almost appears to be a solid line, when in actuality it is over 4000 points. I failed
to check the settings on my GPS, so it was set to track my location every second.
This resulted in my track log being 47% full and battery depleting over 50%,
all in less than 2 hours.

Figure 7: This map shows the track logs of my whole group. The map makes it apparent that
each of our GPS settings were different because the interval between points is
different for each of us. The map also shows the variance in positional accuracy,
as our points do not always match up. At the top of the map at point 4a, you can also
see that Beatriz's GPS shows her as being almost on the shoulder of the highway,
which she obviously was not.

Figure 8: This map shows the track logs of everyone in the class. Rather than having 18 different colors
showing the track log of each individual, I chose to place everyone into their respective
groups and make their symbols the same color. 

Discussion

It was immediately apparent how much of a difference a GPS unit can make. Without a GPS we had to spend time using a map to find the bearing to the next point, have one person always walking ahead and lining them up with the bearing, and we needed to count our pace in order to have an idea of the distance we traveled. With a GPS, each of us could merely walk and monitor the UTM coordinates on our GPS. Once we found the that we could set waypoints, it became even easier since all we had to do was follow the arrow and it counted down the distance to the point. This time we didn't have any difficulties finding the flags because we were lead practically right to them, whereas last week we didn't complete the course because we didn't have full trust in our bearing and didn't keep track of our pace well. Given how difficult it was to traverse the terrain, even on a level surface, it was nice to be able to just set a waypoint and follow the arrow.

The discrepancy between the number and accuracy of points collected by each GPS is apparent in the Group Map (Figure 7). The number of points was due to the fact that we forgot to examine the settings on our GPS, and so each of our GPS's were collecting points at a different rate. My GPS, it turns out, was tracking the location every second, which explains why I had over 4000 points and it almost looks like a solid line. Joel and Beatriz had less than a quarter of the number of points as I did. This is an important lesson. In a matter of 2 hours, my batteries depleted almost 50% and my storage was 47% full, whereas the other two were less than 5% full and didn't use up anywhere close to as much of the battery. Since we were all walking in a single file line, all of the points should be on top of one another. Unfortunately, GPS are not that accurate, as is demonstrated by the map. Since we were walking in a forest, the dense vegetation and tree canopy assisted in hindering the positional accuracy.

By looking at the map of all track logs (Figure 8), you can see that the other groups did not check their settings as well. It can also be seen that everyone followed relatively direct paths, as the curves in a path were mostly the following of the terrain for ease of travel.


Conclusion

Much to our delight, this exercise went much smoother than the week prior. We completed the course in under two hours without a single issue, substantial improvement over last week. However, as shown, a GPS has issues of its own. It requires batteries, has many settings that must be checked to ensure appropriate data collection, and its positional accuracy can vary depending on environmental factors. For this reason it is important to plan ahead and have at least a one other method of data collection available, in case the primary fails, has issues, or is confiscated by Customs.

Assignment 6: Navigation with Map and Compass

Exercise conducted on: March 4th, 2013.

Introduction

This week we had to meet at the Priory, a 112 acre area recently purchased by the University. The maps we made last week were printed out and provided to us upon arrival. The intent of this week's assignment is to learn how to use a map and compass to navigate. Though it was not snowing or raining this time, we still had knee-deep snow to walk through for much of the trip.

Methods

Upon arriving at the Priory, we were instructed to go inside and gather our maps. We were then given a sheet of paper with UTM coordinates on them. The coordinates corresponded to the course we were going to be on. The professor had designed three navigation courses, each with six points. My group was assigned to the first course, and so those were the points we plotted on our map (Figures 1-3). Once each of us plotted our points we were given a briefing on how to use a compass and determine bearing.

Figure 1: Me, plotting our course markers on a map.  We were given a sheet of paper
with a list of each course and the respective UTM coordinates.  

Figure 2: Joel comparing his points on the map with mine, to verify that we each have our
points place correctly.  Two points were placed incorrectly, so it was good that we
compared our maps, otherwise we would have had to fix it in the field.

Figure 3: Beatriz finding the bearing to each point on the map.

When it comes to using a compass for navigation, it is important to know azimuth as well.  The azimuth, or bearing, is an angular measurement based on a circle, and is measured in degrees.  On a compass, North is 0 degrees (or 360), East is 90, South is 180, and West is 270.  Magnetic declination would be taken into consideration, however, Eau Claire, Wisconsin is incredibly close to zero declination.  The compass would then be placed on the map, with the travel arrow parallel with the intended path.  Then, the compass housing is turned parallel with North on the map.

With all of the points mapped and the bearings determined, we headed outside to begin our adventure. We were lead to the first point to ensure that we started at the correct location, and then were left alone. We decided the best way to stay on course would be to split the responsibilities three ways. Beatriz determined the bearing, I walked ahead while she told me if I need to adjust in direction, and after a while I would stop, and then they would follow, with Joel counting the pace. This process went quite well, though it was difficult to follow a straight path due to the trees (Figure 4). In short time we found our first point (Figure 5).

Figure 4: Joel and Beatriz making their way towards me.  Ask can be seen,  it is difficult to travel in a straight
line when there are trees and branches everywhere, along with snow ranging from ankle to knee deep.

Figure 5: Joel and myself (left) at the first point.  The markers are hanging from trees and
can be seen from a fair distance away.  Our bearing took us directly to it.

The second point did not go over so well. We continued with the same method we used to find the first point, this time eventually coming to a valley, with a fairly steep slope. We double checked our map, and it showed the point as being more towards the top of the ridge around the valley. We looked down into the valley and saw nothing, so we thought we may have moved off bearing for a portion of the time. I walked to the East a ways to try and find the point. Multiple times I got my hopes up when I saw flags on trees, but unfortunately they were trees that were marked for other reasons (Figure 6). When I returned to the group we took another look at the map, and felt fairly confident that the flag was all the way down in the valley. Each of us split off and branched in different directions to find it, but to no avail. After about 30 minutes of wandering we all met back up and decided it would be best to go back to our previous point and try again. Just as we were about to head back, Martin, our field supervisor, came to check on us, and was confused as to how we hadn't found the point yet. He took us no more than 10m to the East of where we ended at the top of the valley and pointed down (Figure 7). This is when we learned the lesson to always trust your compass. Though the point appeared to be on the ridge of the valley, all we had to do was look more closely to the valley itself.

Figure 6: Tree with a flag tied to it.  There were quite a few of these out there, and several times
they got us excited thinking it was the marker.

Figure 7: The flag that hid from us.  Due to the snow it is difficult to see the slope of the ravine,
but it is pretty steep.  There were trees that assisted in obscuring it, and had we been coming
from the other side it may have been easier to spot.  However, had we only trusted our
compass we would have found it much sooner.

Unfortunately it was getting quite dark and we were running out of time for the exercise, so Martin brought us with him to show us where the next point would be and to gather the other group on the same course as us (only starting at last point). Once we found the other group we headed back to the building and were done with the exercise. We were very disappointed with having found only one flag, as most other groups finished their courses.

Discussion and Conclusion

Having only found one flag, it was a very frustrating experience. We spent at least 30 minutes wandering around looking for a flag that was right in front of us had we only looked deeper into the valley. However, there were some very important lessons learned from this experience. The first is to always trust your compass. We thought we had followed the bearing properly, but because we didn't immediately see the flag like we did the first time we assumed we must have went slightly off bearing with all of the trees in the way. Had one of us simply decided to slide down the ravine to check it out, we would have found it.

Our second lesson was to ensure we have finer contour lines for future exercises at the Priory. Our map had a two meter interval, while we did have a two foot interval at our disposal. Had we used the two foot interval instead, it is likely that the point would clearly have been in the ravine rather than what appeared to be the ridge.

On the other hand, our navigation method was quite effect. Each person was doing something and it was done in an expedient manner. We look forward to doing another course so we can use this experience excel in the future.  

Assignment 5: Creation of Topographic Map for Land Navigation Exercise

Introduction

This week's assignment was to create a topographical map, using a UTM coordinate system, to be used for land navigation. This report, along with the next couple will not be held to as high of standard, as there will be a fully encompassing report at the end of the land navigation exercises.

The purpose of the land navigation exercises is to learn how to navigate in the natural environment without the use of technology (such as GPS), as current technology relies on batteries to operate, which can be expended, leaving you stranded unless you have other means of finding your way about.

The location of the land navigation exercise is The Priory, a 112-acre mostly wooded area that was a monastery, but was purchased by UWEC in 2011 and converted to a Childcare Center.

Method

The first step we had to accomplish was establishing a pace count. This is necessary for having a semi-accurate idea of how far you are traveling from one location to another when not using high-tech equipment. To do this we measured out a 100 meter distance using our distance surveyor like we used last week, and then counted the number of paces it took us to travel that 100 meter distance. A pace is started from a stand-still and you lead with your left foot, counting with every step of your right foot. Each student did this three or four times to determine their average. My average pace was 64 per 100 meters. This pace count, however, will not be quite as accurate in the field due to the fact that this was on level terrain. Once we are at the Priory, the varied terrain and snow will cause our numbers to increase.

Next, we went into the lab to begin making our maps. The professor provided all of the data we needed to make our map. The data consisted of: a navigational boundary of the Priory, a point boundary which is where the points we will have to locate will be in, 5 meter contour lines, a 2-foot contour DWG file (CAD file), and aerial photographs of the area. The DWG files were obtained in a UWEC survey upon acquisition of the land. The 5 meter contour was created from a 1/3 arc second DEM, which was downloaded from the USGS seamless server. The aerial photographs were obtained from the Wisconsin Regional Orthophotography Consortium (WROC). With all the data provided, we were allowed to choose what we wanted to use.

In order to use all of the data effectively, it is important to ensure all of the data is in the same projection. This is sometimes easy to forget in ArcGIS 10.1, as data is projected on-the-fly. Though this is nice at times, if you forget to check and start running analyses with on-the-fly projections, you can quickly run into errors. Having all of your data in the same coordinate system is vital to the usefulness and accuracy of your maps. While most people are aware of the latitude/longitude coordinate systems, these cannot be used effectively to measure distances between points as their units of measurement are degrees. In order to measure distance, you need a coordinate system that is measured in meters or feet. Being in Wisconsin, we essentially had three useful options: UTM, State system, and State Plane system. In Wisconsin, the state is split between UTM Zone 15 and 16, but Eau Claire is well within Zone 15. State systems and State Plane systems provide greater accuracy in a small area, and are especially good for areas that are near the edge or between two UTM zones. We used UTM Zone 15N with NAD83 datum reference.

With the projection decided, it was time to either ensure the data was already UTM Zone 15N, or project it using the Project tool. It is very important to not confuse Project with Define Projection. Define Projection merely overwrites the coordinate system information, and is intended to be used on datasets that have either unknown or an incorrect coordinate system define. In order to actually convert a dataset from one coordinate system to another, the Project tool must be used. An issue arose with our 2ft contour file, which was a DWG (CAD file). This dataset had an unknown coordinate system, but was unable to have a projection defined. In order to properly load the file we had to add our projected orthoimage first, which set the data frame projection to UTM Zone 15N. In ArcMap 10.1, this means that any further layers are projected on the fly to UTM Zone 15N. As discussed earlier, this is not the ideal method to use, but for what we are doing it will work.

With all of the datasets in the proper projection, it was time to create maps to be used next week in the field. Each of us in the group needed to create at least one map, which we would discuss with our group and decide on which one we wanted to be printed out for use. Both of my maps used the 2-foot contour to provide us with the best idea of what the terrain was like. Figures 1 and 2 show my maps, with Figure 1 having the orthoimage as the bottom layer to show the environment.

Figure 1: Map of the area of interest, using the orthoimage of the area as the bottom layer. The 2-foot
contour lines are used to provide elevation.  A grid system with UTM coordinates overlay the map
to provide a way to navigate the area.

Figure 2: Map of the area of interest, with only the 2-foot contour lines for elevation.  The exlusion
of the orthoimage is intended to provide a simpler map that will be easier to read.  This map also
contains a grid system with UTM coordinates in order to navigate the area.

Discussion

After completing my maps, it was time to meet with the group and decide which maps we wanted to use. We decided on using Joel's maps, as we all liked his use of the colored DEM to show elevation (Figure 3). His second map was also simple and clear, using just the 2-meter and 5-meter contours to show elevation (Figure 4).

Figure 3: Joel's first map that uses a transparent, color-coded DEM to show elevation, and the
orthoimage underneath to assist in visual referencing.

Figure 4: Joel's second map contains 2-meter and 5-meter contours for elevation, and
also shows the location of buildings and the pond.  A grid system with UTM coordinates
is also provided for navigation.

Conclusion

This assignment demonstrated the importance and necessity of ensuring all datasets being used are in the same coordinate system. At the same time it showed the malleability of cartography, which was seen in the differences in the maps each group member made. While the data being used follows strict guidelines, the map itself is a creative endeavor that can have many useful results.