How many polygons of bituminous coal exist, according to this data set?
Next, lets examine geology, and pick up some additional GIS skills along the way. Use Theme > Properties to change the theme name from sd_geol_alb to Geology. Open the theme table for the geology theme. 10) Click in the different rows. As you do so, what happens to the map? Say you wanted to select the first and second most prevalent geology types in South Dakota in terms of area of terrain. 11) Does the table indicate how large each unit of geology is? Therefore, you need to add a field that holds the data for the areal extent of each polygon, or geologic unit. Table> Start editing. Note: If the systems “start editing” choice is grayed out, you need to make sure the files are not “read-only” or archive files. To fix this, go to Windows Explorer, and highlight all of the files in your South Dakota folder. Go to File> Properties, and take off any check marks that appear under “archive” or “read only.” In ArcView: Edit > Add field. Add a field named: Area. Make a numeric field with a wid
