Field Activity #7: Navigation with a GPS Unit

Introduction

This week’s field activity was a continuation of the last two weeks field activities, which involved creating a navigational map and learning to navigate using that map and a compass. The purpose of this week’s field activity was to learn how to navigate using a global positioning system (GPS) unit, without the assistance of a map. To do this our professor provided each person with a sheet of paper that contained a series of points with their latitude and longitude (lat/long) coordinate locations (image 1). Every person was also provided with GPS unit (image 2).

Image 1: Sheet provided to us by our professor with the point’s lat/long coordinate location

 

Image 2: GPS unit used for navigation

 

The area which we navigated had to total of three courses that were all overlapping one another. Two teams traversed on one course at a time with one team navigating from point 1 to point 6, while the other team traversed backwards from point 1 back around to point 2. Navigating from point to point involved matching the lat/long location on the sheet of paper to the lat/long on the GPS unit (image 3). Latitude measures your location north and south, while longitude measures location east and west. Because of this a compass provided in the GPS came in very handy (image 4).

Image 3: Location of lat/long coordinates on the GPS unit

 

Image 4: Compass on GPS used for traversing from point to point

 

 

As mentioned in last week’s activity, as well as Field Activity #4: Distance and Azimuth Survey, before one can use a compass they need to check the magnetic declination of the place they are using it at. Magnetic declination is the angle between compass north and true north. Compass north is the direction the north end of a compass needle points, while true north is the direction along the earth's surface towards the geographic North Pole. Magnetic declination varies both from place to place and with time. In Field Activity #4 we established that the magnetic declination of Eau Claire, WI was 0ᵒ 59’ W. Since 0ᵒ is such a small declination no adjustments to the compass is necessary.

Methods

To begin this activity we first had to locate our starting point. As mentioned above, we did this by matching the lat/long of the GPS unit to the lat/long point 1 provided on the sheet of paper (image 5).

Image 5: GPS unit used to navigate from point to point by matching the lat/long to the sheet of paper with lat/long coordinates for each point

 

Once we reached our starting point we turned our track log on (image 6). Once the track log is turned on the GPS unit begins tracking the route you walk. It is very important to turn this on otherwise you will not end up with any data at the end of your navigation to see how well you traversed from point to point using lat/long coordinates.

Image 6: Location on the GPS where the track log is turned on and off

 

 

After locating our starting position we navigated to the other 5 points (image 7) on our course by matching the GPS unit’s lat/long to the lat/long on the sheet of paper for the next point we were traversing to.

Image 7: Point markings the navigation courses

 

 

To accomplish this as efficiently as possible our team created a system. The system involved one person paying attention to the latitude, one person paying attention the longitude, and the third person kind of paying attention to both. We did this because it’s hard to focus on two separate numbers at the same time. This way it was less confusing and frustrating. If one person was watching their number and realized the value was getting higher instead of lower, or vice versa, then they could let the other team members know and the direction of movement could be corrected.

We also used the compass, located on the same screen as the lat/long coordinates (image 8), to help us get a better idea of which direction we needed to be walking. As mentioned earlier, this is because latitude measures your location north and south, while longitude measures location east and west.

Image 8: Lat/long coordinates and compass located on same screen for more efficient tracking of directional movement

 

 

Once the final point was navigated to the track log was turned off. It was important to turn the track log off because otherwise anywhere you went after the navigation activity was over would be recorded. This would make it extremely difficult to know your course when the file was downloaded to the computer. 

After the navigation was done every person downloaded their data from their GPS unit onto a computer as shapefiles. To do this I used a program called DNR GPS was that was already installed on the computers (image 9).

Image 9: The DNR GPS program used to download my track log points onto the computer

 

 

The following steps will lead you through the process that was executed to get the data from my GPS unit onto the computer.

1. First, the GPS unit needed to be connected to the computer with a USB port cord (image 10).

Image 10: GPS unit connected to the computer with a USB port cord

 

2. Then, the “Tracks” tab was selected (image 11).

 Image11 : “Tracks” tab selected

 

 

 3. Next, the “GPS” tab at the top of the screen was selected and “Connect to Default GPS” was chosen (image 12).

Image 12: “Connect to Default GPS” was chosen from the “GPS” dropdown menu

 

4. Then, the computer located the GPS unit that was connected to it (image 13).

 Image 13: Computer located the GPS unit that was connected to it

 

 

 5. Next, the “Track” tab at the top of the screen was selected and “Download” was chosen (image 14).

Image 14: “Download” was chosen from the “Track” tab dropdown menu

 

6. Then, the computer downloaded the track log data from the GPS unit (image 15).

Image 15: Computer downloaded track log data from GPS unit

 

7. Next, the data was saved into my personal class folder on the W drive as a point shapefile (images 16 -18).

Image 16: “Save to” then “File” is chosen from the “File” dropdown menu

 

Image 17: Navigate to my class folder to save my data as an “ESRI Shapefile”

 

 

Image 18: Chose to save my data as a “point” shapefile

 

 

After the track log was downloaded into my class folder I created a geodatabase, in my class folder, using ArcCatalog. Here, I imported my shapefile as feature class. Next, I brought my track log into ArcMap (image 19).

Image 19: Track log brought into ArcMap as a point shapefile

 
 

After checking the projection of my track log I saw that is was in GCS_WGS_1984 (image 20). It was projected in this coordinate system because that’s what the GPS unit I was using was set up as.

Image 20: Track log downloaded in a GCS_WGS_1984 coordinate system

 

 

However, the professor instructed us to have our track logs projected in UTM Nad 83. So, I projected my track log into NAD 1983 UTM Zone 15N (images 21 and 22). This is because Eau Claire, WI is located in UTM Zone 15 North.

Image 21: Using the toolbox in ArcMap to project my track log feature class into the correct projection

 

Image 22: NAD 1983 UTM Zone 15N as the chosen projection for my track log


 

 

Finally, I was able to bring my track log into a new blank map in ArcMap (image 23). By doing this, the data frame for the map was set to this projection due to project on the fly.

Image 23: My track log after the projection

 

Now I was able to create maps that depicted the navigation routes for myself, my group, and all groups combined.

Results

Map 1 depicts my individual track log. It shows that overall navigation from point to point was a little curvy. I certainly didn’t walk in a straight line from point to point.

Map 1: My individual track route

 

Map 2 illustrates my groups track logs. Here we can see that overall we followed similar paths. However, there are certain areas in our routes that show times when we split up slightly from one another.

Map 2: My groups track routes in relation to one another’s

 

Map 3 shows the routes for all 6 groups on all 3 courses.  Colors yellow, orange, and red depict one team, while colors purple, blue, and green depict the other team who are both navigating on the same course. If you refer to course 1, the course my group traversed, you can see the difference between the two groups’ routes that navigated the course.

Map 3: All six groups track routes in relation to each other

 

Discussion

In short, after reviewing that results of all the maps we can see that navigation from point to point wasn’t perfect form anyone, or any group. We can also see in every course both teams traversing the course took different routes. This goes to show that navigating using a GPS unit probably isn’t the most effective and efficient navigational technique. It would be interesting to see how the results would differ if a map depicting the landscape was involved in the process.   

Conclusion

Overall, I found this form of navigation to be much harder than using a compass and pace count. I found that a map would’ve been much more helpful with this exercise than having with the compass and pace count exercise. Having a map that depicted the landscape terrain would’ve assisted the group in knowing if the point being navigated to was on top of a ridge, or in a valley. This would’ve been helpful because it had just snowed a lot that day and throughout the prior weekend. This made traversing the landscape very difficult and tiring.

I also found that it would’ve been helpful to have had a plastic baggie to put the piece of paper in with the point’s locational data. This is because the water from the snow made the paper difficult to read (image 24).

Image 24: Paper with point locational information was hard to read due to it getting wet from the snow

 

 

I found that towards the end of the navigation I was asking my team members what the numbers were to make sure I was reading them correctly. If I would have been reading them wrong we could’ve ended up walking in the wrong direction. That would have really stunk!

Like the previous activity we found that it was important to keep an eye on the lat/long onour GPS units. This is because the courses intersected one another, so at times you would come to a point on your course that wasn’t your intended target. Being that this navigation exercise was more difficult than the last one, seeing a point on your course made it easy to be lured to it without thinking about whether it was yours or another team’s point.  We actually made this mistake and traveled out of our navigation route to get to a point we thought was ours. When we got to it there was another team there. After debating whose it was we realized we were wrong. This goes to show the importance of paying attention and following your coordinates. It also shows how weather conditions can influence how you think and work. Like I stated earlier there was a lot of snow and traversing the hilly landscape with the difficult navigation technique all led to us navigating poorly towards the end when we were tired.