Creating Contours from a DEM file in GIS

Lab: Creating Contours

Lab Files Needed: Mississippi Roads Shapefile, Desoto County Boundary Shapefile, Desoto County DEM, Mississippi Population Density, Shelby County Boundary Shapefile, City of Memphis DEM

Elevation data comes in a variety of formats at varying resolutions. Much of the elevation data you will access from public agencies will be in the form of a Digital Elevation Model, or DEM. These DEM files are raster data where individual pixels contain elevation data. The resolution of the DEM determines how precise the data. The following steps will utilize DEM files for creating contours

1. Add the Desoto County Boundary to a blank map.
2. Add the Desoto County DEM file to the map. The DEM will indicate the highest and lowest elevations for the area in the table of contents. Lighter areas will represent higher elevations while darker areas represent lower elevations
3. In the ArcToolbox, navigate to Spatial Analyst>Surface>Contour or search “Contour” in the search menu.
4. Select the DEM as the raster input and set the contour elevation to 20. This will create 20 foot contours for the entire DEM coverage area.
5. Save the newly exported data by right+clicking on the data in the table of contents and selecting Data>Export Data. Save the file in your preferred location as a Shapefile
6. Adjust the Symbology of the newly created polylines by right clicking on the layer and selecting properties. Select the symbology tab, select categories, unique values and add the contours to the list. Utilize the green to red color ramp to better view the data.

For the completion of this second lab assignment, create an 11×17 layout and export the map to a known scale. Be sure to label the contours and put a title, scale bar, scale text, and north arrow in the layout. Save it as a pdf and submit via email as “lastname_firstname_lab02”

Contour Dialog in ArcToolbox:

 

Lab Observations:

Not all public data is flawless. There might be quirks or gaps in the data that will need to be adjusted before proceeding with your project. Select the editing icon to open up the editor toolbar in ArcMap. Start Editing the contour data and delete erroneous linework in the drawing. Finalize and save edits to the data.