Activity #5: Learning Distance Bearing Navigation and Development of a Field Navigation Map

Introduction

In this exercise, students will learn the basics of field navigation using only a map and compass. After having learned how to properly use a compass, two maps will be made with grids displaying different coordinate systems. One map will have a geographic coordinate system (lat/long) and the other will have a projected coordinate system in UTM. The maps will contain the same area, The Priory in Eau Claire, WI, and will be used for actual field navigation later in the semester. The two types of coordinate systems will then be compared and analyzed.

Methods/Discussion

- Learning Distance Bearing Navigation-

A compass is one of the most basic navigation instruments available and works with any map or as a stand-alone device. The simplest explanation for what a compass is would be a strip of metal that is floating in liquid that reacts to the earths magnetic field so that the red portion of the metal strip points towards magnetic north. There are different kinds of compasses but the focus of this exercise is on the orienteering compass.

Figure 1: An orienteering compass. Each part is labeled. The base plate and compass dial are clear. The magnetic needle will be red and white. The orienting arrow and direction of travel arrow may be red or black depending on the style of compass.

There are essentially three main components of a basic orienteering compass: the clear baseplate, rotating compass dial, and a magnetic needle. On the baseplate there is a direction of travel arrow and an index line. Inside the rotating compass there is an orienting arrow and meridian lines. Surrounding the rotating compass are degree ticks and the four cardinal directions. The magnetic needle has two sides, the red side is north and the white is south. All the functions of each part of the orienteering compass will be described later.

To begin, the compass shows the four cardinal directions: North, East, South, and West. Each cardinal direction corresponds with a specific degree, see figure 2. Understanding these numbers can quickly help determine if the correct bearing is taken when in the field.

Figure 2: The cardinal directions are colored red. The compass can be broken down into smaller increments (NNE, NE, ENE, etc.) then the 90 degree brakes of the cardinal directions and are labeled on the figure.

A bearing is the direction, measured in degrees from magnetic north, form one location to another. To take a bearing, hold the compass straight out in front, with the direction of travel arrow pointed towards the location of interest, and hold it steady. Then rotate the compass dial until the red (north) portion of the magnetic needle is within the orienteering arrow (see figure 1). The number that is now posited at the Index line is the bearing. Following this bearing will lead to the location of interest. This technique is used in the field when the location can be viewed with a persons eye.

Figure 3:Finding a
bearing from a map. 

When the location is too far away or too hidden by obstacles to be seen, or simply a position drawn on a map, the orienteering compass can be used along with a map to find the bearing. Assuming there are two places are known on the map, a start and end, the bearing can be found. Place the compass on the map with the direction of travel arrow pointing from the starting position to the ending position. Try and get the direction of the compass to fall as accurately as possible through the two points, use a straight edge and pencil if needed. Then turn the compass dial so that the orienteering arrow is pointed straight up, or to the north. If the map has a grid, the meridian lines in the compass dial can be lined up to increase the accuracy. With the orienteering arrow pointing north and the compass still pointing towards the ending point, the bearing can be recorded (the number at the Index line).

Just like when taking azimuth data in the previous exercise, magnetic declination comes into play, when using a compass and map. When using a map drawn to true north to find declinations to use in the field, it is important to either add or subtract the declination of the area of interest from the map bearing. The magnetic declination for Eau Claire,WI was calculated earlier in Field Activity #4: Conducting a Distance Azimuth Survey., and is 1.08139 W and as such should be added to each map bearing.

Knowing how to use a map and compass is not the only skill needed to successfully naviate in the field. Establishing a pace count is also important. A pace count is the number of paces it takes to cover a known distance, typically 100 meters. A pace is the distance covered each time one foot (the individual decides either the right or left) hits the ground. My pace count for 100 meters is 63. Having established a pace count, a person can roughly estimate the distance traveled along their bearing.

A handy technique to make things easier when navigating the field is to find a feature (tree, statue, anything recognizable, etc.) that falls along the map bearing and travel towards that instead of constantly watching the compass. At times there may be impassable features (pond, marsh, endangered animal habitat, etc.) along the bearing and there are several methods to bypass this issue. The first is finding a feature along the bearing like stated above, and walk around the impassable feature to the known feature along the bearing and continue. If there is no feature along the bearing, and multiple people are in the field then a person can walk around the impassable feature and become the known feature along the bearing (making sure to take a back bearing to be sure the individual is along the bearing line). If there is only one person in the field, then that individual can approach the impassable feature and turning 90 degrees multiple times, walk around the impassable feature taking a pace count for each direction traveled. By walking the same distance back  to the bearing line as the person walked away from the bearing line will result in the individual being at least roughly back on track. See figure 4 for an illustration of this technique.

Figure 4: How to deal with an impassable feature when following a map bearing. Keeping track of a persons pace and turning 90 degrees three times will result in knowing roughly the distance traveled pass the feature and will result in the person being back along their map bearing.

Any questions regarding using a map and compass that are not addressed here are most likely found at this website: Compass Basics: An Introduction to Orientation and Navigation  All pictures were taken from this website.

- Development of a Navigation Map - 

 

 The next task for this exercise is to create two maps of the Priory in Eau Claire, WI, to be used later in the semester for actual field navigation. These maps were created in ArcMap 10.2 and used data from the UWEC Geography department. Each map needed certain criteria (grid, proper size, north arrow, data sources, etc.) but it was up to the student to decide what to include on the map itself. When creating a map for field navigation, it is vital to include only what is needed as superfluous data can cause the map to become cluttered and difficult to read. Because of this, I choose to include 5 meter contours and a semi-transparent DEM (digital elevation model). Using these two layers, the topography of the Priory is easily distinguishable without making the map too busy, which the addition of aerial imagery often does.

 

Figure 5: The DEM of Eau Claire, WI used for the maps, and for creation of the 5 meter contour lines. The small orange/brown box that can be seen in the upper portion of the DEM is the Priory study area.

 

 

It began with a raster based DEM, which means the model is made up of a grid of squares with each square having a height value and representing a different color. Using the Contour tool in the ArcToolbox  under Spatial Analyst Tools >  Surface > Contour, contour lines of varying size can be created. For this map, 5 meter spacing was chosen.

 

Figure 6: The Contour Tool and it's location. Here different rasters can be chosen and the size of the contours can be decided.





 

After the contours were made, they were clipped to appear only the study area using the Clip Tool found in the ArcToolbox under Analysis Tools > Extract > Clip. The layer to be clipped was the recently created 5 meter contour shape file and the layer to clip from was a navigation boundary polygon from the Geography Department.

 

Figure 7: The Clip Tool. Used to clip a feature within the boundaries of another. Used to clip 5 meter contour lines to within the study area, since the lines outside the study area were not relevant to the exercise.

 

 

 

Figure 8: The resulting clipped contour lines, semi-transparent DEM (by changing the display options by right clicking the layer and choosing Properties > Display), and the study area polygon.

 

 

 

Now the work in Data View was done and the Layout was assembled. Each map needed: a north arrow, a scale bar and absolute scale, geographic and projected coordinate systems, data sources, name, date, watermarks, and a grid displaying a geographic coordinate system  for one and a projected UTM coordinate system for the other. To add a grid, right click inside the data frame and choose Properties > Grids. At this point new grids can be created or existing grids can be turned on or off. Clicking "New Grid..." will the Grids and Graticules Wizard window in which three different types of grids can be created. The geographic coordinate system map was made with the Graticule option and the project coordinate system map was made with the Measured Grid option. Going through the wizard allows the user to change the appearance of the lines and division ticks. Once the grid is created the labels can be formatted accordingly.

 

Figure 9: Creating a new grid. The window on the left is the Data Frame Properties where the user can select pre-existing grids or make a new one. The window on the right is the Grids and Graticules Wizard window which will guide the user through making a new grid.

 

 

Figure 10: By highlighting a grid and clicking the Properties... option in the Data Frame Properties window, another window appears that lets the user customize the options for the grid. Most importantly for this exercise the labels can be changed in the Labels tab. All the options for labels are expanded and shown in this figure.

 

 

The rest of the criteria for the map was added by clicking the Insert tab on the main toolbar and choosing the appropriate item.

  

 

 Figure 11: The map with the grid displaying a geographic coordinate system.

Figure 12: The map with the grid displaying a project coordinate system.

 

 

The reason two maps were created is to compare the effectiveness of each type of coordinate system in preforming field navigation. Geographic coordinate systems are good for small scale maps and looking at features on a broad scale, while projected coordinate systems are best used for large scale maps and examining features at a finer scale. It would be assumed that the map with the UTM projected system would be better for the purpose of the field navigation activity later in the semester.