Erin Miller December 12, 2011 GIS/GPS Applications Cycling the Continental Divide: Determining the Optimal CourseI. Introduction to Problem I am an avid cyclist and I have noticed that the city of Austin bike maps are a welcome addition to the cycling community. They improve one’s ability to determine a bike course based on traffic volume, road conditions and elevation gain. While these maps are comprehensive and useful there is currently a lack of maps and information for those seeking to bike outside of a single city. As I plan on cycling the United States continental divide this summer, determining the best route from southern New Mexico to the U.S./Canadian border based on types of roads available while minimizing the elevation gain over the course of the ride would greatly improve my pending adventure. II. Data Collection The data needed in order to determine the best continental route is shapefiles of the state borders, cities, continental divide and primary/secondary roads for New Mexico, Colorado, Wyoming, and Montana found at the U.S. Census Bureau (http://www.census.gov/cgi-bin/geo/shapefiles2010/main) as seen in Fig. 1: Figure 1: Locating/Downloading Data Additionally, elevation data (DEM) of the area of interest is needed at a scale that is reasonable for the foot print of the project, determined to be 90m. This was found at http://www.cgiar-csi.org/data/elevation/item/45-srtm-90m-digital-elevation-database-v41 and was opened via GoogleEarth.There were 9 files needed in order to cover the latitude and longtitude desired. On the website they were files 14_03-14_04, 15_03-15_06, and 16_04-16_06. III. Data Processing A. Loading Data The first step was to load all of the data into the GIS map, entitled Final. This was done by right clicking on the layers tab in the Table of Contents, selecting + Add Data, navigating to where it was saved (external hard drive), selecting it, and clicking the button “Add” as seen in Fig. 2: Figure 2: Adding Data B. Combining DEM Data For the DEM data, we need to combine the 9 files. For this project they were grouped into a Southern Zone (New Mexico & Colorado) and a Northern Zone (Wyoming & Montana). In order to combine the DEM data we use the tool Mosaic to New Raster located in Data Management Tools>Projections & Transformations>Raster>Raster Dataset>Mosaic to New Raster as seen in the red box in Fig. 3:Figure 3: Combining DEM Data via Mosaic to New Raster tool In the “Input Rasters” select the data that covers New Mexico and Colorado (15_05-15_06 and 16_05-16_06). For Output Location, place in your folder where you are keeping the project in a new folder labeled “SRTM”. For Raster Dataset Name with Extension name it CONMUTM13. For Spatial Reference for Raster, select the icon on the right, choose the select button, choose Projected Coordinate Systems, UTM, NAD 1983, and then select NAD 1983 UTM Zone 13N.prj and hit “Add” as seen in Fig. 4 in the red box: Figure 4: Selecting projection for new MosaicSay 1 for “Number of Bands” and leave everything else as it is. Repeat this process for the Northern portion (14_03-14_04, 15_03-15_04, and 16_06) except this time on projection select UTM 12N and name it MTWYUTM12. The project should look similar to Map Image 1: Map Image 1: DEM data C. Editing Road Data 1. Ranking Data Next we need to prepare the road data so that when we rasterize it will be in the format we want. This requires eliminating roads that are not defined. To start, in the TOC, right click on the roads shapefile and select “Open Attribute Table”. From there, click the “Select by Attributes” tool. In Method leave it as Create a new selection, and make the statement “RTTYP= “blank”. This will select all of the roads that are unclassified and therefore should not be considered in our analysis. We need to delete this roads and can do so by selecting “ Start Editing” on the Editor toolbar. When prompted, select the roads shapefile. From here, delete selected. Make sure and click “save edits” on the editing toolbar afterwards. We want to rank the remaining data in order to aid us in our least cost path analysis. We can do this by first making a column in the attribute table in order to convert the letters defining the roads into values that can beranked. In order to add a column, open the attribute table, in the table options select “Add Field” naming the field “Rank”, leave Type as Short Integer (Fig. 5). Figure 5: Adding Field in Attribute Table Now we need to fill in the Rank column based on data in the RTTYP column. The 6 letters we have are U: Major highways which are a 4 in desirability, S: State highways, a 1 in desirability, M: municipal roads a 3 in desirability, C: county roads a 2 in desirability, and O: back country roads which are a 6 in desirability. These rankings are based on our personal goals for the road trip, but may vary depending on the goal one is focusing on. The easiest way to go about filling in the Rank column is to “Select by Attribute” in the table by the RTTYP column starting with “Letter U”. From here go to the frame that only shows the selected entries (blue box at the bottom of the table). Since we are working with Major Highways, we want to fill in the Rank column with the number 4. We can do this by placing our cursor where the column is labeled rank and right clicking. This gives us a list of options. We want to use field calculator as seen in Figure 6: Figure 6: Filling in Rank column with appropriate valuesOnce Field Calculator is open, double click on “Rank”, click on the equals sign and enter the #4, clicking “OK” afterwards seen in Figure 7: Figure 7: Filling in the Rank column via Field Calculator This has filled in the Rank column with the #4 for only the entries that were labeled “U” in the RTTYP column. Repeat these steps for S-O with the assigned numbers given in the paragraph above. Since we have two different projections in our project, we need to make two different roads rasters and define the projection for both the North & South Portion of the map. To do this, simply go to ArcCatalog, and navigate to the Roads file. Select the roads file, right click on it, hit copy, and past in the same directory. Rename the file and its copy, the original should be North and the copy as South. Make sure that when we define the projections that, the appropriate