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 10.5). 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.
Task 1 guides you through the process of converting a USGS DEM in SDTS format into an ArcInfo grid. The DEM file in the TAR.GZ zipped format.
1. Please note that there are many DEM online sources, for example, https://nationalmap.gov/elevation.html. The Geography's Center for Spatial Analysis & Research (CSAR) also maintains an ArcGIS Server on which you can find several DEM/DSM data layers. Please follow this link to learn how to access the data on the CSAR server. For this lab, you will only use the data the instructor provides.
2. Go to I:\Students\Instructors\Geoffrey_Duh\GEOG4593-DTA\Lab1\STDS folder and copy all the files to your lab1 folder. 1646292.DEM.SDTS.TAR.GZ is a l0-meter DEM for an undisclosed area in Portland, Oregon. Also save the 1646292.DEM.SDTS.TXT file in your lab1 folder. Use Notepad to view the contents in the TXT file. You will need the information in this file to answer some questions of the lab.
3. Now we need to unzip (decompress) the gz file. Double-click on the gz file and check "Select the program from a list". Click OK and then click on the "Browse" button. Navigate to "C:\Program Files (x86)\7-zip" folder and select "7zFM.exe". The 7-Zip File Manager window will appear. Click on the Extract icon, specify your output folder (e.g., C:\Users\MyODIN\Lab1\) and click OK. This will unzip the gz file to your lab1 folder. (Note: You can unzip gz files using WinZip as well, but we don't have WinZip installed on our lab computers.) You will find a new file with the .TAR file extension. Now, create a folder called "elevation" under lab1 folder and move the .TAR file to the elevation folder and repeat the procedures above to unzip the data (Use the "edit/select all" option to extract all files). When done, there are several SDTS data descriptive files (DDF) in the folder.
4.
You can find a pdxhydro.zip file containing the 1:24K USGS DLG hydrography
dataset in the files you copied from the I: drive. Now you can unzip the zip
file. The hrdrography data is stored in ArcInfo COVERAGE format. Use the browse
button to navigate to the data files in the pdxhydro folder. The data files
all have the HY01 prefix. Double-click any of the files. Save the coverage to
your workspace.
5. Now, we need to convert the DEM in SDTS format into an ArcGIS GRID format. To convert a raster dataset in SDTS format to GRID format, you can add the SDTS raster (e.g., 7974CATD.DDF) to ArcMap (at least on version 10 or later) and then export the raster layer as a GRID. Make sure the output file path (i.e., workspace) does not contain spaces (i.e., " ").
* Note: If you have ArcInfo Workstation installed on your computer, you can use the "Import From SDTS" tool to perform the conversion. Start ArcMap. Click "ArcToolbox Windows" button to open the ArcToolbox window. Double-click the Import From SDTS tool in the Coverage Tools/Conversion/To Coverage toolset. In the Import From SDTS dialog, use the browse button to navigate to the data files in the elevation folder. The data files all have the 7974 prefix. Double-click any of the files. The Input SDTS Transfer File Prefix in the dialog should list 7974. Change the output grid name to pdxdem and save it in your lab1 folder (not in the elevation folder). Click OK to execute the conversion.
6. Launch ArcMap. Add pdxdem and the pdxhydro vector layer (the polyline featureclass in the COVERAGE) to the data frame. Change the color of hydro polylines to blue. The two data sets should register spatially.
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\Shares\gisdata\PortlandRLIS\RLISArchive\2016\2016_May\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? In your own words, write a short description on how Z tolerance works in the Raster to TIN tool.
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.