Introduction
In next week's exercise, we will be navigating through the Priory in Eau Claire. In order to prepare, just as in any other navigational task, we needed to create a tool to help us navigate. Sometimes this tool can be a GPS, maps, or even the sun and stars as seafarers often and primarily used as late as the late 1700s. For our navigation through the Priory, we made a map from which we can find locations by estimating foot steps as an approximate, defined distance (pace count method) and both a compass and GPS.
Methods and Results
We were placed randomly into groups of three. Each group member created two maps of their own using the UTM coordinate system for our area and the WGCS in decimal degrees. We then handed in our best map for printing to use in next week's lab.
We used data from a Priory Geodatabase created by Dr. J. Hupy. Our first step was to decide which features to include on our maps. From this data, I decided to use Priory aerial imagery for a basemap and 12-foot interval contour lines as any interval less than that cluttered the map and any more would not give us an accurate reading of elevation changes. I also used the Priory boundary to depict our study area and clip contour lines to the area of interest. I left out other irrelevant feature classes in the geodatabase such as the no shooting zone.
I added all the necessary map information including:
- north arrow
- scale bar (meters)
- RF scale
- projection name
- coordinate system name
- labeled grid
- basemap
- list of sources
- my name
The first map utilized WGS84 (World Geodetic System 1984) (Fig. 1). WGS is a coordinate system in which the coordinates are generated by using the Earth's ellipsoid shape as a spatial reference (2). The positions units are given in decimal degrees. Maps utilizing a WGS are typically used for operations in large study areas.
 |
| Fig. 1: Priory Map utilizing GCS_WGS_1984. |
For the second map, I created gridlines representing coordinates in the NAD 1983 UTM Zone 15N. Universal Transverse Mercator grids (UTM) split the world into 60 zones, each only 6 degrees in longitudinal width. This lessens the distortion in the area due to projection from the spheroid shape of the Earth to a flat map surface (1). Because the grid lines cover a more localized region and the associated minimal distortion, UTMs are typically used for smaller study areas such as states and counties. Metadata for both maps was then created in Map Document Properties (Fig. 3).
 |
| Fig. 2: Priory map utilizing NAD 1983 UTM Zone 15N. |
 |
| Fig. 3: Metadata for the GCS map (right) and the UTM map (left). |
Discussion
For this project, we had to think critically about the amount and type of information we included in our maps in order to navigate effectively and map points within a relatively accurate margin in a later exercise. I decided to include 12-foot contour lines, a boundary of the study area and aerial imagery. Having too much information on the map would crowd the map and make navigating more difficult. It is for this reason, I included 12-foot contour lines as opposed to 2-foot contour lines to show elevation data useful in pace-counting as your step changes with any slope. I added aerial imagery as a base map as this may help visually find features and a boundary of our study area for good measure of the area we should remain inside during our navigation exercise.
Conclusion
This week's lab was meant to solidify knowledge on designing maps. It is critical to understand the coordinate systems, projections, and grids in order to create a map that will be most useful in a particular scenario. It is also important to understand the reason for making the map and what it will be used for as this will effect the amount and type of information that must be represented in the map. The purpose of each map will dictate somewhat how the map should be designed and it is important to understand this purpose in order to create a map that will be most efficient in completing the goals of its purpose.
References
1) http://pubs.usgs.gov/fs/2001/0077/report.pdf
2) http://www.unoosa.org/pdf/icg/2012/template/WGS_84.pdf
No comments:
Post a Comment