The purpose of this lab was to create two functional navigation maps that will be used in a future exercise. Navigation requires two sets of tools. First, tools to perform the actual navigation are needed. These tools range from the stars to GPS systems, or even a simple map. Second, a type of location system is needed to value to geographic locations. Location systems often consist of some variation of a coordinate system and some type of a projection. In this lab two types of coordinate systems were used: UTM coordinate system and a world Geographic Coordinate System of Decimal Degrees.
Methods
Two different navigation maps were created during this lab of the same study area using different coordinate systems: UTM and GCS.
Study Area
The study area that was created into the navigation maps was a piece of land called the Priory. The Priory is an area of land owned and operated by the University of Wisconsin- Eau Claire. This land is used as a private dormitory and a 120 acre wooded area that is used as a children's nature preserve. Maps of the Priory in relation to the University of Wisconsin- Eau Claire and the Priory itself are in Figure 1 and Figure 2.
Figure 1. Image highlighting the location of the Priory in reference to the University of Wisconsin-Eau Claire main campus.
Figure 2. Image displaying the appearance of the priory campus.
Coordinate systems are reference systems used to identify the locations of land features, imagery, and geographic observations. Coordinate systems allow the collaboration of different data sets when they share the same coordinate system.
Coordinate systems are defined by four key features:
- The measurement framework
- It can either be geographic, meaning that spherical coordinates which are obtained from measurements from the earth's center. Otherwise the measurement framework can be planimeteric meaning the earth's coordinates have been projected on to a 2D flat surface.
- The units of measurement
- Latitude and longitude measurements typically use decimal degrees while, projected coordinate systems use feet or meters usually.
- The definition of the map projection for projected coordinate systems.
- The properties of other used measurement systems
- examples: spheroid reference, datum, standard parallels
UTM
The UTM, Universal Transverse Mercator, coordinate system is a specialized version of the Transverse Mercator projection. This projection operates under the basis that the globe is divided into 60 zones located in the north and south. Each zone encompasses 6° of longitude and has its own central meridian. A specific UTM zone is selected based on which UTM zone the study area resides in. Within each UTM zone there will be minimum distortion of those lands. The 48 continuous states of the United States fall with in 10 different UTM zones. These specific zones are highlighted in Figure 3.
Figure 3. The UTM zones of the 48 continuous states of the United States.
GCS
The GCS or Geographic Coordinate System utilizes a 3-D spherical surface to define locations on earth. GCS utilizes an angular unit of measure, a prime meridian, and a spheroid based datum. Longitude and latitude lines calculated by the angle measured from the center of the earth to the location on earth's surface. These angles are often written as decimal degrees, Figure 4 shows a model of the earth divided by lines of longitude and latitude.
Figure 4. Model of the globe demonstrating how longitude and latitude lines are used to calculate decimal degrees of locations on earth.
Results & Discussion
The following navigation maps were created by using either a UTM or GCS coordinate system.
In order to create the UTM coordinate system map, all of the datasets had to be projected to the same projection. All of the data sets for the UTM priory map, the basemap, contour intervals, and study area boundary, were all projected in the North American Datum 1983 of UTM zone 15N. A 50 meter grid of the UTM intervals was added to the map for navigation reference purposes. The map created can be seen in Figure 5.
In order to create the GCS coordinate system map, all of the datasets had to be projected to the same projection. All of the data sets for the GCS priory map, the basemap, contour intervals, and study area boundary, were all projected in the Geographic Coordinate System North American 1983. A decimal degrees grid of the longitude and latitude lines was added to the map for navigation reference purposes. The map created can be seen in Figure 6.
The maps were created with a cautious eye as to not allow the map to become too busy. Often times maps are created using all available data sets and then the purpose of the map can become lost and the map can become so busy it is unusable. The base map was used in both maps because, when navigating it can be useful to match the terrain you are seeing with the terrain on the map for location purposes. The contour lines were clipped to be only slightly larger than the navigation boundary as to reduce the business of the map that would have occurred if the contour lines had covered the whole map. The navigation boundary was included because it is important to know the general area you are located and narrow down the possible locations for which you are locating.
Figure 5. A UTM coordinate system map displayed using a 50 meter UTM grid of the Priory.
Figure 6. A geographic Coordinate system map displayed using a decimal degrees grid of the Priory.
This lab provided valuable insight into how to create navigation maps and the importance of understanding how different coordinate systems can be used. Often now we rely on technology to fulfill our navigation needs through the increasing applicability of GPS navigation systems. But, technology is not always readily available for use. It is important to know how to use simple navigation maps to fulfill our navigation needs.
Sources
Coordinate systems, map projections, and geographic (datum) transformations. (n.d.). Retrieved March 06, 2017, from http://resources.esri.com/help/9.3/arcgisengine/dotnet/89b720a5-7339-44bo-8b58-0f5bf2843393.htm.
Map Basics. (n.d.). Retrieved March 04, 2017, from http://www.edc.uri.edu/nrs/classes/nrs409509/Lectures/4MapBasics/Map_Basics.htm.
Priory Hall. (n.d.). Retrieved March 04, 2017, from http://www.uwec.edu/Housing/residencehalls/priory/priory-hall.htm.
What are geographic coordinate systems?. (n.d.). retrieved march 05, 2017, from http://desktop.arcgis.com/en/arcmap/10.3/guide-books/map-projections/about-geographic-coordinate-systems.htm.
