Lab 1: Digital Terrain Data Models
This lab has three separate tasks that will let you explore different digital terrain data models, including DEM, 3D featureclass, and TIN. You will download a DEM from an Internet website. Task 2 involves the use of points and a DEM to learn how ArcGIS handles 3D objects. In Task 3, you will convert a DEM to a TIN data model. The exercise will be done using ArcGIS (Version 10.1). This is your opportunity to explore the software and to get acquainted with the interface. Use the help system to learn about the different software options and functionality. Spend some time browsing the websites that you visit in this lab. Type the answers to all questions at the end of each task, attach your map, and submit them to the instructor by the due date.
Before you start the first lab, you need to know where to save your lab data. You are only allowed to put data in the C:\Users\[your_odin_ID] folder on the computers in CH469 or CH475. To make the data accessible when you use a different computer, you can put the data on your H: drive or a USB portable drive. Create a folder for lab1 in your designated folder and make sure the file path does not contain spaces for the labs in this class. We will use ArcInfo in some labs. ArcInfo cannot handle file paths that contain spaces.
Task 1 guides you through the process of downloading a DEM and converting it to a grid. The DEM is in SDTS format, and the SDTS files are in the TAR.GZ zipped format.
* Hydrography DLG - Click on this link - hydrography, then select hydrography and click 903780.HY.sdts.tar.gz. Save the file in your folder.
* DLG Master Data Dictionary - Click on SDTS DLGs require Master Data Dictionary. Save the file (00MASTERDD_LRG.SDTS.tar.gz) in your folder.
* Alternatively, you can go to the USGS Geographic Data Download website (http://eros.usgs.gov) to find the data set.
Use the layers' Properties dialog in ArcMap and the data in the txt file you downloaded to answer the following questions.
You will use the DEM you just created to assign elevation data to a RLIS fire station layer.
1. Add I:\Research\Samba\GISdata\RLIS\2013_Aug\PLACES\fire_sta.lyr to the same data frame you created in Task1. Click the "List by Selection" icon on the left panel of ArcMap, make the fire stations layer selectable and all other layers non-selectable. Use the Select Features by Rectangle tool to select only the fire stations within the extent of the DEM.
2. Right-click on the fire_sta layer and select Data/Export Data. Check the data frame option button so that the output uses the same coordinate system as that of the data frame (i.e., DEM's coordinate system. Type in the output shapefile's path and name (e.g., C:\Users\MyODIN\firestations.shp) and click OK to finish the feature extraction process. Make sure you have read/write access privilege to the path you specified in the output field. When done, open the attribute table of firestations and make sure it has 14 records. (Alternative method: This method requires the use of "project" tool to reproject the fire station layer to the projection of the DEM. Click Show/Hide ArcToolbox Windows to open the ArcToolbox window in ArcMap. Double-click the Select tool in the Analysis Tools/Extract toolset. Click on the down arrow of the input features field and select fire_sta from the dropdown list. Set output feature class as firestation shapefile in your lab1 folder. Click OK to continue. When using the PROJECT tool in Arctoolbox, you need to specify two transformation methods: NAD_1983_To_HARN_WA_OR and then NAD_1927_To_NAD_1983_6.)
3. Start ArcScene. Add firestations and pdxdem to the data frame in ArcScene. (Do you see a flat map of DEM and points that you can spin around when you drag the cursor?) Double-click on pdxdem layer to open the layer properties window. Click on the Base Heights tab and check "Floating on a custom surface" and make sure the surface points to the pdxdem layer. Now use the "Factor to convert layer elevation values to scene units" option to set the correct Z (i.e., elevation) exaggeration factor. You will need to know the scene's horizontal unit and the DEM's elevation unit to set the value correctly. However, for more dramatic visual effects, you can exaggerate relief by using a larger factor value. Click on the Symbology tab and set Histogram Equalize as the stretch method. Click OK to continue. Double-click on the firestations layer to open the layer properties window. Click on the Base Heights tab and set it to float on the pdxdem. Click OK. Now you should see a 3D rendering of the DEM and the firestations points.
4. Open the ArcToolBox window in ArcScene and make sure that the Spatial Analyst extension is enabled. Double-click the Extract Values to Points tool in the Spatial Analyst Tools/Extraction toolset. Select firestations as the input point feature and pdxdem as the input raster. Set output as firest_z shapefile in your lab1 folder. Check "Interpolate values at the point locations." Click OK to continue. When the process is completed, open and compare the attribute tables of firestations and firest_z. Answer Question 1 below now.
5. Go to Customize/Toolbars on the ArcScene pulldown menu and open the 3D Analyst toolbar. Now we need to add a tool called "Features to 3D" to the 3D Analyst toolbar. Go to Customize/Toolbars on the ArcScene pulldown menu and select "customize..." Select the commands tab from the customize dialog window. Click the 3D Analyst in the left panel (i.e., categories) and drag "Features to 3D..." commands from the right panel to the 3D Analyst toolbar. When done, close the Customize window and click on the Feature to 3D command you just added to the toolbar. Set firest_z as the input feature and set pdxdem as the source of heights. Save the output as firest_3d.shp in your lab1 folder.
6. The firest_3d layer is automatically added to the data frame. Is it displayed as a flat map of points? Double-click on the firest_3d layer. Click on the Base Heights tab and check its setting. Open and compare the attribute tables of firestations and firest_3d. Answer Question 2 below now.
7. Double-click the Add XY coordinates tool in the Data Management Tools/Features toolset in ArcToolBox. Set firestations as input features and click OK. Use the same tool to process the firest_3d layer. Open and compare the attribute tables of firestations and firest_3d. Answer Question 3 below now.
1. Click the Search Window icon in ArcGIS (ArcMap, ArcCatalog, or ArcScene) to show the Search window. Search for "Raster to TIN" tool. Select the Raster to TIN (3D Analyst) from the search result window to open the tool. Select pdxdem for the input raster, specify pdxtin for the output TIN, change the Z Tolerance value to 10, and set the Z Factor to match the Z unit and X, Y unit of the DEM data. Click OK to run the command.
2. You can view pdxtin in a variety of ways in ArcMap or ArcScene. In ArcMap, select Properties from the context menu (i.e., right-click menu) of pdxtin. Click the Symbology tab. Click the Add button below the Show frame. An Add Renderer scroll list appears with choices related to the display of edges, faces, or nodes that make up pdxtin. Click "Faces with the same symbol" in the list, click Add, and click Dismiss. Uncheck all the boxes in the Show frame except Faces. Make sure that the box to show hillshade illumination effect in 2-D display is checked. Click OK on the Layer Properties dialog. With its faces in the same symbol, pdxtin can be used as a background in the same way as a shaded relief map for displaying map features such as streams, vegetation, and so on.
1. In step 1, you use 10 as the Z tolerance in the Raster to TIN conversion. What happens when you change the tolerance to 125?
2. How many nodes and triangles are in pdxtin that were created with different Z tolerance values?
3. Make a map (or maps) showing the TINs you created with different Z tolerance values. Please follow common cartographic standard when preparing the maps.