In order for an individual to navigate through an area, an individual requires several critical tools. First, they require a way to orient themselves, be it with a GPS, a compass, the stars, or the positioning of the sun in the sky. Secondly, that individual requires a location system, typically a navigation map. This location system is constructed utilizing and projection, usually with an accompanying coordinate system. The purpose of this lab was to develop skills in navigation map construction and increase the understanding of coordinate systems and their projections. To this end, two navigation maps would be constructed of the area surrounding the University of Wisconsin-Priory Hall in Eau Claire, Wisconsin (Figure 1), utilizing the UTM coordinate system and the GCS WGS 1984 coordinate system. These were to be used at a later date for navigating the area.
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| Figure 1: A reference map showing the University of Wisconsin-Priory Hall location using a Google Maps imagery (left), and a topographical map (right). The navigation map area is denoted by the red rectangle. The address of Priory Hall is 1190 Priory Rd, Eau Claire, WI 5470, and its latitude and longitude are 44.7654109° N, 91.5136289° W. |
In order to properly construct the navigation maps, it was critical to first understand the differences between the projection and the coordinate system of a map, and to understand the primary function of each. A coordinate system is the three dimensional representational surface of the globe which uses collected data points to link locations in the real world to points on the coordinates system, which is then used to define locations on earth. Components of a geographic coordinate system include an angular unit of measurement, a prime meridian, and a datum (based off a spheroid). A projected coordinate system utilizes a linear unit of measurement, a map projection, the parameters of the map projection, and a geographic coordinate system. A map projection is the two dimensional representation of an a three dimensional area on a globe. Depending on the area of interest in a study, the corresponding projected or geographic coordinate system must be selected . This is critical to map construction, as a projected coordinate system and a geographic coordinate system are imperfect representations of the real world. When transferred to a two dimensional surface, like a map, distortion occurs in the space outside of the focus area as the three dimensional model is stretched and altered to fit the projection. To compensate, many coordinate systems have been created on national, state, county, and local levels so that distortion can always be kept to a bare binimum, no matter the area of interest.
Methods
First, a new map file created in ArcMap, with the layer properties being set to the "NAD_1983_UTM_Zone_15N". This would ensure all feature classes brought into the map layer would be projected into the NAD 1983 UTM Zone 15N projected coordinate system, with a Transverse Mercator projection. Then, a raster dataset of the Priory and surrounding area, "grdn45w092_13", was incoperated into the map. Utilizing this raster dataset and the necessary tools, both a hillshade and a contour shapefile with a contour interval of two meters were created and implemented into the map. Next, a boundary shapefile of the navigation area was added to the map. This was used to clip the contour file to only the navigation area. Afterwards, the raster, the hillshade, the navigation boundary shapefile, and the clipped contour were all reprojected into the NAD 1983 UTM Zone 15N projected coordinate system in order to ensure they were in the correct coordinate system. In the layout view, a measured grid was added to the map layer, with the coordinate system being set to that of the data frame. In addition, the x and y axis intervals were set to 50 meters, and the origin was set to that of the original coordinate system. With the primary map components implemented, the remainder of the work on this map was dedicated to map design. The width and height of the map document were set to 17 and 11 inches, respectively. An RF scale was included. A scale bar was included, with the equivalent value of paces being included, as taken from an average pace count of 100 meters. The average pace count was 66 paces per 100 meters. The raster was set to a partial transparency in order for the hillshade to appear beneath it. The grid and contour lines were both redesigned to make them more easily visble. The coordinate system and projection were included on the map. Traditional map elements like a north arrow, a watermark, and the data source were included. The grid labels were altered to both fit the other map elements and prominently display the 50 m change between intervals. After all reorientation and resizing of the map elements was completed, the map was titled Priory UTM Field Navigation Map and exported.
To contrast the UTM map with a coordinate system that has been more familiar up to this point, a Decimal Degrees Field Navigation Map was created of the navigation area by altering the UTM map. First, the data frame projection was changed to the GCS WGS 1984 geographic coordinate system. Then, all of the relevant feature classes (contour lines, raster, hillshade, navigation area shapefile) were reprojected into this geographic coordinate system. Then, the UTM grid was replaced by a Graticule Grid which used Decimal Degrees and whose origin was set to that of the coordinate system. The interval and grid labels were altered several times till they displayed the changes in Decimal Degrees up to the fourth decimal and at an interval of 1". Similarly to the UTM map, a field map titled Priory Decimal Degrees Field Navigation map was constructed, using many of the map elements of the UTM map. Most elements, like the RF scale and the scale bar, needed only to be resized. The only elements completely changed were the grid, as mentioned previously, the labels for the map's coordinate system and projection, and the title. After resizing and reorientation was complete, the map document was exported.
Results
The UTM Field map was designed primarily for ease of use and to minimize clutter (Figure 2). Rather than use an image of the navigation area for a background, the raster dataset was set as partially transparent with the hillshade behind to simulate the terrain This would allow both the contour lines and the grid lines to more easily appear against the background while still showing the terrain. The contour lines were set at a two meter interval to accurately portray the terrain while also eliminated any excessive contour lines. A traditional scale bar was included. Map elements, like the scale bar, RF scale, pace count, watermark, source list, and coordinate system label, while included, were kept to a minimal size and delegated to the corners of the map to minimize the amount of visual interference associated with reading the grid labels. Speaking of which, the grid lines were set to 50 meter intervals to once again maximize the number of grid lines while still making the map easy to read. The labels were oriented so that all but the top labels were arranged horizontally so that they could easily be read by the navigator. Only the top labels were arranged vertically, as some of the bottom labels were lost when they were arranged horizontally. In addition, the labels were set so that the 50 meter intervals would always be the last or second to last digit displayed. This was again done to maximize readability. The projected coordinate system, NAD 1983 UTM Zone 15N, was created in 1983 and focuses its projection between 96°W and 90°W of North American (Spatial Reference). Since the navigation area falls within this zone, this projected coordinate system is ideal for minimizing distortion of our map. One traditional map element that was not included was a reference map. This is because the navigator will have little use for a reference map, as navigation map will only be utilized from within the navigation area, whose location is already known. It would only serve to create clutter.
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| Figure 2: A UTM navigation map of the area surrounding the University of Wisconsin - Priory Hall. The projected coordinate system is NAD 1983 UTM Zone 15N, and the grid lines have an x and y interval of 50 meters. |
The Priory Decimal Degrees Field Navigation Map (Figure 3) shares many of the same aspects of the UTM map. All map elements of the UTM map, such as the RF scale or the watermark, are included in this map as well. It is designed with ease of readability in mind and utilizes the same raster and hillshade as a background. What has changed is the coordinate system and all map elements relating to this. The map is displayed in the geographic coordinate system GCS WGS 1984, a fairly standard coordinate system created in 1984. There exist a couple problems with this coordinate system. First, when projected, it does not focus on the navigation area. This has resulted in distortion and slight reorientation of the navigation area on the map. Second, by relying on Decimal Degrees as a unit of measurement, the grid labels mark intervals using a unit that is non-optimal for this scale. As a result, all changes between intervals are denoted up to the fourth decimal place of a degree, as this is the scale the map is operating at. Out of the two navigation maps generated, this is the less effective of the two for navigating the Priory area.
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| Figure 2: A Decimal Degrees navigation map of the area surrounding the University of Wisconsin - Priory Hall. The geographic coordinate system of the map is GCS WGS 1984, and the grid lines have an x and y interval of 1". |
Sources
Coordinate systems, projections, and transformations. In ArcGIS Pro. Retrieved 3/8/2017, from http://pro.arcgis.com/en/pro-app/help/mapping/properties/coordinate-systems-and-projections.htm
Google Earth View. Retrieved 3/8/2017, from https://www.google.com/maps/place/University+of+Wisconsin-+Priory+Hall/@44.7654109,-91.5136289,17z/data=!4m5!3m4!1s0x87f8be07fda0a431:0xb2c38ea0334a21d!8m2!3d44.7654114!4d-91.5114395
Kupy, J. (2017) Field Activity #5: Development of a Field Navigation Map. Eau Claire, Wisconsin.
NAD83 / UTM zone 15N: EPSG Projection. In Spatial Reference. Retrieved 3/8/2017, from http://spatialreference.org/ref/epsg/nad83-utm-zone-15n/
What are map projections? In ArcGIS Desktop. Retrieved 3/8/2017, from http://desktop.arcgis.com/en/arcmap/10.3/guide-books/map-projections/what-are-map-projections.htm
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