Exercise 4: Development of a Field Navigation Map

Introduction

This field activity involves creating a field navigation map, which will be used as a reference later in the semester for the navigation activity. The location of the field activity was the Priory area. Two maps were created using the UTM projection and a geographic coordinate system of decimal degrees. The maps also included other information such as contour intervals and elevation. 

Methods

Using geographic coordinate systems is a crucial part in the cartography process. Without having all of the data in the same coordinate systems, they will not accurate project over the top of the other. A geographic coordinate system is a 3-D spherical surface to define locations on the earth. A point is defined by its latitude and longitude typically expressed in degrees or decimal degrees. The spheriod approximates the shape of the earth, while a datum defines the position of the spheriod relative to the center of the earth. Popular datums that are used in North America are NAD 1927 and NAD 1983. Projected coordinate systems are most popular when projecting a map. They are defined on a flat, 2-D surface (Figure 1). Unlike GCS, there is lengths, angles, areas, and is identified by x,y coordinates.

Figure 1. Examples of different planes that can be used for projected coordinate systems. 

Various data on the Priory was provided in order to create the maps. It included 2-foot contour lines, Navigation boundary, raster data of the site, elevation, and LiDAR data. Once the particular data was placed in the maps, the projections had to be the same across all of the data. These particular maps used NAD83 Wisconsin Transverse Mercator in order to minimize the distortion of the study area. This was a simple choice in the areal image was already in the NAD83 projection. 

To prevent business and congrestion in the map, two were created each showing a different characteristic. Each map included the Navigation boundary on top of the areal image. But the first map included the 2-ft contour lines and the second had an overlay of the elevation for the study area. Each map also included a grid one in decimal degrees of 2.5", and the other in 200 meters. For future Navigation activities, a pace count was calculated and included on the details of the map as well. This particular pace count was 65 steps per 100 meters. A scale bar (meters), information on the coordinate system, and a north arrow was added in order to show the details needed for the map navigation purposes. 

Results/Discussion

The first map included the 2-ft contour lines that were overlaid on the areal image, shown in Figure 2. The navigation area was defined by a red boundary line. The grid of 2.5 seconds (decimal degrees) was also used in this map. If this map was done over again, the contour lines would be at a greater distance of 5 ft. or even 10, so it is not as busy looking. Due to some error in making that possible, the contours stayed at 2-ft. 

Figure 2. Field Navigation Map of the Prior with 2-ft contours and decimal degree grid lines.

The second map was to show the elevation of the Priory study area. The Navigation boundary was still the same. However, the grid size was changed to 200 meters. The scale bar is especially important for the map in Figure 3, because the grid is also in meters. The study area is in a place where elevation is not that high. The minimum elevation in the red zone is 194 meters and a maximum of 424 meters in the green areas. The transparency was altered in order to still be able to see the areal image of the study area.

Figure 3. Field Navigation Map of the Priory including elevation and 200 meter grid lines.

Summary/Conclusion
By including grids at various forms of measurement, the Navigation maps will have alternative ways of identifying points in the study area. The elevation and contour lines will also be useful in getting a feel for the topography of the Priory. Future data that was created directly from the source and not provided, may be easier to manipulate in order to achieve easier reading maps.