Creating a Navigation Map

Objective and Background

The objective of this exercise was to design a navigation map of the Priory, an area of land owned by the University of Wisconsin-Eau Claire, for a future course assignment. A secondary objective was to gain a better understanding of how projections and coordinate systems may effect navigation.

A coordinate system is a sort of grid that uses a series of numbers to determine a point in space. For example, on earth location is determined using latitude and longitude values.Different coordinate systems may be used depending on what is being mapped, what projection is being used and other factors.These maps use two different coordinate systems

WGS-1984 Web Mercator Auxilary Shpere- This coordinate system has become the standard for web mapping applications and is the system utilized by Google Maps. This coordinate system has many advantages and disadvantages that are associated with the traditional Mercator projection.

NAD1927-UTM zone 15N- This coordinate system is part of the Universal Transverse Mercator or UTM system that breaks the earth into 60 north-south zones, each covering six degrees of latitude. Each zone can be mapped with a specific transverse Mercator projection with very little distortion.

Methods:

There were a few key terms that needed to be understood prior to creating the navigation grid

1. Define Projection- This tool changes the information about the current projection, however it does not change the projection itself. You basically give it a new name. The project tool is need to actually change the projection.

2. Project/Project Raster- These two tools are used to actually change the map projection in the map document. Project Raster is obviously used for rasters and the Project tool is used for vector data.

3. Contour- This tool was used to create contour lines in the map document. This was done using elevation information from Lidar data of taken from the study area. In these maps, each contour line represents a 5 foot change in elevation.

After creating the contour lines, the next step was to create a navigation grid using ArcMap software. The grid can be created under data frame properties, which can be accessed by right clicking within the data frame. Our first map created was a navigation map that used a gradicule grid. The grid lines were spaced one second apart and the decimal degree labels were given four decimal points. 

The second map used a measured grid with each grid line being 50 meters apart. Instead of using decimal degrees, this units on this map stand for how many meters north of the equator and west of the prime meridian a point is. The final step to creating the maps was adding all of the necessary map elements

Results

  

Figure 1
Priory Navigation Map in Decimal Degrees

For the navigation map I choose to have my contour interval set at 5 feet, therefore every yellow line represents a change in elevation of roughly five feet. The grid spacing of every one second is ideal because the map is not too cluttered however there are still plenty of coordinates to navigate by. For this maps background I choose to use an areal image of the study area with about 70% transparency. This provided some visual reference to the map without making it appear too cluttered.

Figure 2
UTM Priory Map

This map is similar in design to the first map, however it uses a different coordinate system. This graph has a grid with spacings every 50 meters. Because this map does not utilize decimal degrees, degrees minutes and seconds are not measured. This will be the main map used for navigating during the lab exercise. One design error I would correct is the map background. I used two separate black and white images with about 70% transparency and there is a significant amount of overlap between the two images. In the future I would perform a mosaic of the two images in a program such as Erdas Imagine.

Conclusions: 
Conclusions that may be drawn from this assignment include the fact that making navigation maps can be quite challenging. The cartographer needs to understand which coordinate systems and projections to use in order to insure that the map remains accurate. There is a fine balance between the map being too cluttered or hard to read and being to vague and impossible to navigate by.