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USA GY 461 - Geology of the Cheaha Mountain, AL, 7.5' Quadrangle Project

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IntroductionStep 1: Create Project FileStep 2: Georeference the Scanned Field MapStep 3: Create Geodatabase and Feature ClassesStep 4: Create the Initial Lithology Polygon and Border in ArcMapStep 5: Complete the Lithology and Contacts Feature Classes Step 6: Add the Structural Data to the Map from AccessStep 7: Add Megascopic Fold TracesStep 8: Using the DEM with Spatial AnalystStep 9: Setup the Layout and PlotGEO/GY461 Applied GIS: EnvironmentalGeology of the Cheaha Mountain, AL, 7.5' QuadrangleProjectIntroductionThis project will consist of converting a geologic map and geologic database into a digitalgeologic map with ArcGIS. This map will display the various rock units exposed at the surface asa polygon topology. The different types of contacts and megascopic structures will be composedof linear topologies, whereas structural symbols indicating the orientation of bedding, lineations,etc., will be composed of a point topology. The project area falls within the boundary of theCheaha Mountain, Alabama, 7.5' quadrangle, a region that contains some of the most ruggedtopography in the southeastern Appalachians. After the geologic map is complete, you will add aDigital Elevation Model (DEM) to the project so you can gain a 3D perspective of therelationship between the geology and topography.Step 1: Create Project FileTo begin the project create a folder named “CheahaMountainGeology” under the“C:\ArcGIS_Data\{your initials}\” folder. Download the ZIP archived files from the below linkto this new folder:http://www.usouthal.edu/geography/allison/gy461/gy461_project_resources.htmDownload the “Project2.exe” file at this site, and then extract the files to your folder. The fileswill consist of a georeferenced DRG of the Cheaha Mt. area (o33085D7.tif), and a scanned imageof the field map that a geologist has used to trace the geologic contacts and added labels for thegeologic polygons. The scanned map will need to be georeferenced using the same methodsempolyed in the 1 project. stStart ArcMap at this time to create a project file names “CheahaMtProject.mxd”. In this filecomplete the following tasks:1. Right-click on the “Layer” in the left window and select “Properties”. Set thefollowing:“General” tabName = “Geology of the Cheaha Mountain, Alabama, 7.5' Quadrangle”Reference scale = 1:24,000“Coordinate System” tabSystem = NAD_1927_UTM_zone_16N2. Insert the DRG topographic base map (o33085D7.tif). Do not create “pyramids”. MakePage -1-GEO/GY461 Applied GIS: EnvironmentalGeology of the Cheaha Mountain, AL, 7.5' QuadrangleProjectsure that the coordinate system of the DRG matches the project coordinate system. Youcan check by right-clicking on the DRG name in the left window, selecting “Properties”,and then the “Source” tab. You can scroll down to find the “Spatial Reference” for theraster.At this point you should save your project file to your folder.Step 2: Georeference the Scanned Field MapThe next step will be to georeference the scanned field map. First you will need to create the 2.5'latitude and longitude reference points in a spreadsheet (as we did in Project 1). Figure 1contains an image of the completed spreadsheet (use the “LatLongCalc_24K.xls” spreadsheet).Export the reference points to “ReferencePointsCheahaMt.dbf”, and then add the “cm-geo.tif”raster file to the project. Proceed to use the Georeference toolbar to generate the TFW file for thefield map, and then re-add it to the project. Have your instructor check the RMS value for thegeoreference before you create the TFW file (“Update Georeferencing” option). A typical resultfor a 5 reference point georeference is displayed in Figure 2. A properly georeferenced rasterfield map should appear very similar to Figure 3. Note that in this figure the DRG topographicbase map is turned off, and that the reference points are set to a large size (40) so that they arevisible when zoomed to the extents of project. You should not set them to this large size- in factthe reference points will need to be set to a size of approximately 12 points when you areworking through the georeferencing steps. Step 3: Create Geodatabase and Feature ClassesIn this step you will create a geodatabase that contains the following feature classes:Feature Name Geometry Field Name Field Type DescriptionWaterBodies Polygon Type Text (50) Water BodiesLithology Polygon LithologicCode Text (50) Geology polygonsContacts Line ContactType Text (50) Geologic contactsBorder Line N/A N/A Quadrangle borderMegascopicStructures Line StructureType Text (50) Large fold traces*StructureData Point N/A N/A Orientation data*StationData Point N/A N/A Station markers* Created automatically with the XY data plotting tool.Page -2-GEO/GY461 Applied GIS: EnvironmentalGeology of the Cheaha Mountain, AL, 7.5' QuadrangleProjectAt this time start ArcCatalog and navigate to the “CheahaMountainGeology” folder. Using thesame technique as in Project 1 create a new geodatabase file named “CheahaMtGeology.mdb”.From that point proceed to create the feature classes described above. Make sure that thecoordinate system for all features is set to UTM NAD27 zone 16 as in Figure 4.When all of the feature classes have been defined, close ArcCatalog and return to ArcMap.Proceed to add the “Water_Bodies”, “Lithology”, “Contacts”, “Border”, etc., feature class to thelayer window with the “Add Data” toolbar button. Remember that these features exist as “child”folders inside the geodatabase file (“CheahaMtGeology.mdb”), therefore, you must navigate tothe .MDB file, and then “open” it to see the sub-folders.Note that the “StructureData” and “StationData” feature classes will be automatically createdlater with the “XY data tool” so you do not need to define them manually as you did with theother feature classes. Step 4: Create the Initial Lithology Polygon and Border in ArcMapIn this step we will begin to digitize the beginning polygons and line work of the geologic mapproject. Start ArcMap and set edit mode by choosing “Edit > Start Editing” from the edit toolbar(if the edit toolbar is not visible, turn it on by right-clicking on the gray tollbar area above themain project window. In the editor toolbar set the task to “Create Features” and the target to“Border”. Now activate (“Editor > Snapping”) and set up the snapping environment as indicatedin Figure 5. Turn off the


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