GPS Navigation

Introduction
Over the past few weeks, our Geospatial Fields Methods class has been exploring different land navigation techniques at The Priory.  First, the traditional technique of using a map and compass was used to navigate to six different point markers in a wooded area.  This week a Garmin eTrex GPS unit was used to navigate to six different points.  The GPS units had the tracking feature on, which was used to create maps and an animation showing the routes of students through the woods.  Next week we will be participating in a paintball activity that involves navigating to as many points as possible.  

Methodology
In preparation for last week's field outing, we needed to establish our pace count and create the navigation maps that we were to use out in the field.  Our pace count was established by marking off a distance of 100 meters and counting the number of paces it took us to walk it.  I found my pace count to be 65.  To create the navigation maps, data such as a orthophotograph, two-foot contour lines, five-foot contour lines, and a DEM was used.  A UTM grid was also placed over the map to aid in the navigation.  On the day of the field event, we plotted the locations of the points that our group was assigned to navigate to.  Straight lines were then drawn from point to point, and a compass was used to measure the bearing.  We then went out in the field and began our navigation event.  Our group utilized a three-person system for the exercise.  One person had the compass and would direct a person to walk to a specified location on the bearing.  The final person would then walk to that person and count the number of paces to estimate the distance traveled.    

This week, we were to use GPS units to navigate to the points rather than using the traditional land navigation techniques using a map and compass.  Each student was assigned a Garmin eTrex GPS unit for the activity.  The unit would be used to locate the navigation points that we were assigned and to track the routes that were taken while navigating to the points.  My group was assigned the points on course 3, and started at point 1B and then went to point 2B.  The other group that was assigned to course 3 started at point 1B and went to point 6B.

Table 1. Navigation Points

My group utilized the UTM coordinates to navigate to the points.  To get to the points, we generally began by navigating to the correct x value, and then walked to arrive at the correct y value.  A recent snowstorm made walking slow and a bit difficult.

Figure 1. Hannah and I examining our GPS units at a point marker.

After we navigated to all of the points, we returned to the parking lot where the class was congregating and turned off the tracking on the GPS units.  This data was then uploaded as a shapefile using the Minnesota DNR Garmin Application.  The shapefile was uploaded in the NAD 1983 UTM Zone 15N projection to be consistent with the other files that were used for mapping of the priory area.  Each student's track log was then imported into a feature dataset which allowed for access of all of the files for everyone.  This data was then used to create maps displaying the track log from my GPS unit, the track logs for my group, and a map containing the track logs of everyone in the class.

Map 1. Track log from my GPS unit.

This map shows the route that I took during the field navigation event.  Symbology was used to display the beginning of the track in a lighter color.  The color then gradually becomes darker as the track progresses.  This data was then used to create an animation of the track.  To do so, the file was selected as a time track under the properties.  The animation toolbar was then used to create and export the video.  The video can be found here: http://www.youtube.com/watch?v=iP7FNiIi3xk.  The files from the rest of the students in the class were added into ArcMap and maps were created to show their track logs.

Map 2. Group GPS Navigation Map

This map displays the track logs for Hannah and me.  Mitch's file was not in the file when it was accessed.  As you can see, Hannah's track log had much fewer points, and is most likely due to a difference in the increments that the GPS unit took points.  

Map 3. Class track logs.

Discussion

After the completion of this field outing, it was apparent that navigation with a GPS is easier and faster than traditional navigation with a map and compass.  GPS navigation does not require any preparation time, and it is much quicker in the field because a person can continuously walk and not have to worry about walking to a certain spot on the bearing and count the number of paces.  It also can be accomplished easily by oneself, whereas in the traditional method, a three person group is ideal.  Another advantage of GPS navigation is that a waypoint can be created on the GPS and it will tell you which direction and how far to travel to this location.  We did not do this during our navigation exercise, but this would have been very helpful and effective to do.   

Even with this benefits of GPS navigation, we did run into a few minor issues in the field.  It was very easy to misread some numbers when walking and looking at the GPS which led us a little out of our way a couple times.  An example of this can be seen in the video of my track between points 3, 4, and 5.  When using UTM coordinates, it is important to remember that the x values increase as you move to the east, and y values increase as you move to the north.  A map accompanying the GPS unit can be very helpful to visualize this when determining the direction to travel.  Finally, GPS technology can not always be relied upon so it is important to have an understanding of traditional navigation techniques.  The batteries in the unit could die, or you could be in an area where it is difficult to obtain a reliable signal.      

Navigation with a Map and Compass

Introduction
The objective for this week's exercise was to navigate through the woods to a series of points using a map and a compass.  This exercise is the follow-up activity to last week's prep work, consisting of the creation of maps and the establishment of each person's pace count.  

Methodology
The preparations for this week's field activity took place last week with the establishment of a pace count and creation of maps of the area of interest.  To establish each student's pace count, 100 meters was marked off in a parking lot.  We then walked the distance and counted the number of paces it took.  I walked the distance three times, and had a consensus pace count of 65.  Maps were then created of the area of land around the Priory using a variety of data sets (Maps 1 and 2).

Map 1. Priory Navigation Map with DEM and Two-Foot Contours

Map 2. Priory Navigation Map with Orthophoto and FiveMeter Contours

As a group, we chose to use Hannah's map in our navigation exercise (Map 3), as well as Map 2.

Map 3. Hannah's Navigation Map

 The field event took place the following week on March 4th.  A snowstorm was moving into the area, but there were only a few flurries during the exercise.  As previously mentioned, our goal was to navigate to five different points using a compass and the maps that we had created.  The first step in the process was to plot the points on our maps using the UTM coordinates that were given to us.  In attempting to do so, it was evident that the grid that Hannah put on her map was not correct.  This put our group in a quandary because there was no way for us to plot the points.  Luckily, we were able to use another group's map.  After the points were plotted on the new map that was given to us, a straight edge was used to draw lines connecting each of the points.  These lines were used to calculate the bearing.  To do so, the compass was placed on top of the map facing the direction that we wanted to travel.  The dial on the compass was then turned so the lines were facing straight up to the top of the map.  This process was completed for each of the five points on the course we were given.

Image 1. Mitch and Hannah Plotting Points

The scale on the map was then used to draw an estimate for the distance between each of the points.  This would prove to be very useful in the field because we could use our pace count to estimate how much further we would have to navigate.

Map 4. Approximate Location of Navigation Points

After our points were plotted, and the bearing and distances were calculated, we set outside to begin our navigation.  We went to our starting point and were to navigate to the designated points where there was an orange marker and a paper punch to show that we made it to each point.  Our method of navigation began with Mitch using the compass and dialing the bearing that we had calculated earlier.  He would then have Hannah walk to a spot (usually a specific tree) on that bearing.  I would then walk in a straight line to Hannah and count the number of paces to provide us with an estimated distance traveled.  We continued this process until our destination was reached.  Image 2 and 3 depict Mitch standing next to the first marker and directing Hannah to a tree on the bearing to our second point.

Image 2. Point Marker 

Image 3. Hannah Walking to a Tree

Discussion
Overall, the navigation event went very well for our group, as we were able to utilize a method that allowed us to move to the points quickly and efficiently.  However, there were a couple minor issues that we had to overcome.  The pace count that we established was done in a flat parking lot, and was not very conducive to estimating accurate distances when walking through the woods.  There were many hills that we had to walk up and down, as well as many trees and other obstacles that made walking in a straight line difficult.  When walking between points four and five, we came across some ponds that were fenced off.  In order to accurately maneuver around them, we counted a number of paces to the side of them.  Once we were around the ponds, those same number of paces were walked sideways to get back on the correct bearing. As mentioned earlier, we also the grid issue on Hannah's map that did not allow us to plot the UTM points.  Experiencing this shortcoming has stressed the importance of reviewing every detail before going out in the field.  

The maps that we prepared were great resources in the field.  The aerial imagery was very helpful in determining what type of terrain we were in and should be going to.  The DEM symbology and contours were also useful for tracking our progress on the map.  We had to walk up and down a few hills, and this information allowed us to make an accurate estimate of our location in terms of the points we were navigating to.  The point data we were given had the elevation in meters listed, and Map 2 that I created was useful because the five-foot contours were labeled.  For future navigation exercises, I would create maps very similar to the ones that we created for this event because the information we included on them was very helpful in the field.  One change would be to include the grid on both maps.  When making a map, it is important to have all of the data layers in the same coordinate system to insure accuracy.  Finally, making sure the correct grid is used is essential.

Conclusion
The navigation event conducted at the Priory went very well for me and my group.  Once the points were plotted on maps that were created, a compass was used to calculate the bearing in which to walk to successfully locate the next point.  Distances were also estimated and related to pace counts that had been previously established to approximate how much further we needed to travel to find the point.  We were able to effectively navigate to the points via teamwork and the information that was included on the maps.   The one main issue we encountered was the inaccurate grid that did not allow us to plot the points on the maps that we had.  This was an example of learning the hard way that all details and information should be carefully evaluated to ensure the greatest possibility of success in any line of work.

Field Navigation Part One

Introduction
This weeks assignment consisted of preparation for a field navigation exercise that will take place at the Priory.  This land, purchased by the university to be a day care facility, is located to the south of the city of Eau Claire.  The image below shows that the land that we will be navigating through is mostly wooded.

Image 1. Area of Interest

 

The activity will consist of a series of points that we will need to navigate to using a compass and maps that we created.  We will not be using a GPS, as the purpose of the exercise is to learn to navigate without the aid of technology.  Since this area is mostly wooded, a GPS might not be very accurate anyways.

Methodology
The first step in our preparations involved establishing every person's pace count, which is the number of steps taken in a given distance.  This will be useful for our navigation because we will not have a GPS available, and we can use our pace count to tell how long of a distance we are walking.  A laser rangefinder was used to find a distance of 100 meters in a parking lot, and the end points were marked with snow.  Each person in the class then walked the distance, keeping track of the number of normal paces that they took.  After walking the distance three times, I found my pace count to be 65.  It should be noted that this was done on a sidewalk, and that a pace count might differ when walking through the woods and avoiding obstacles.

After the pace counts were established, our next task was to create the maps that we would use in our navigation exercise.  There was a suite of data sets available, but it was up to us to determine what would be useful to have on a our maps.  The data available consisted of: a topographic map of the region, color and black and white orthoimages, two foot contour intervals, five meter contour intervals, shapefiles of the area of interest, and a DEM.

When working in GIS, it is extremely important to be aware of coordinate systems.  ArcMap uses on the fly projections to project data that are in different coordinate systems.  This is nice for displaying data as you are using it, but any analysis should be done with data in the same coordinate system.  It should be noted that it is best practice to work with files in the same coordinate system to prevent errors and inaccuracies.  There are many different coordinate systems, and the appropriate one should be chosen to work best with the area of interest.  The area of interest for this project is very small, so a state plane or UTM coordinate system is ideal.  The UTM 15 North coordinate system was selected.  This coordinate system will work well because we can create a UTM grid and overlay that on top of our maps to aid in the navigation.

During the beginning of map construction, the two foot contour data was giving us problems.  This file was converted from a CAD data set, and did not have a projection.  When it was added to the other layers in ArcMap, it was not displayed.  To solve this problem, a blank document was opened, and the two foot contours were the first file added.  After this, the other data layers were added in the UTM 15 North projection.  I decided to make two maps for this navigation exercise.  The first consisted of the DEM, two foot contours, and a UTM grid.  The DEM covered a much larger spatial extent than our area of interest, so the Extract by Mask tool was used to extract the area of interest from the final file.  This smaller area had a smaller range of values, which made for better symbolization.

Map 1. Navigation Map with DEM and Two Foot Contours

The second map was to have a much more simple design.  For this, the orthophoto was used as the base, and the area of interest and five meter contours were overlaid.

Map 2. Navigation Map with Orthophoto and Five Meter Contours

    Each person in our three person group created their own maps, and then as a group we were to collaborate and choose two maps that we liked best for our navigation.  My second map of the orthophoto and five meter contours was chosen, as well as Hannah Bristol's map pictured here.

Map 3.  Hannah's Navigation Map

Discussion
This weeks assignment was based on preparations, and a more detailed account of the exercise will come next week after we actually partake in the activity.  The preparatory work did have value in terms of establishing a pace count and discussing how it can be used for navigation, as well as stressing the importance of knowing and understanding coordinate systems.  When working with different data sets, they should always be in the same coordinate system.  If not, the project tool should be used to convert them.  Also, the appropriate coordinate system should be used, depending on the extent of the area of interest.  For a small region like this, the UTM Zone 15 North works very well.  A state plane coordinate system could also be used, but one must be aware of the extent of the zones, because you do not want the area of interest to overlap into two or more zones.  Finally, map elements were an important aspect of this exercise.  We were to determine which files we wanted to have on our maps without them being too cluttered.  Scales, north arrows, grids, and the sources of data also had to be included.