INSTRUCTIONS FOR MAKING 3D,.DWG CONTOUR LINES

Transcription

1 INSTRUCTIONS FOR MAKING 3D,.DWG CONTOUR LINES A TUTORIAL FROM SPATIAL AND NUMERIC DATA SERVICES NICOLE SCHOLTZ AND GEOFF IVERSON Overview... 2 A. Get a Digital Elevation Model (DEM)... 3 B. Open ArcMap, load the DEM into it C. Convert Z values to feet D. Smooth the DEM E. Create contour lines F. Convert Xs and Ys to feet G. Convert your contour lines to 3D H. Export to CAD format library Page 1 of 45 rev: August 2012

2 OVERVIEW This process allows you to make contour lines for a United States- only site of interest. The contour lines will be in 3D and in.dwg format; you can use them in AutoCAD, Rhino, 3DS, or any other program that can read.dwg files. Other options exist to integrate topographic (elevation) data into your work. If a 3D,.dwg vector file is not the output you re looking for, talk to a SAND librarian. You will use software called ArcGIS to do this. GIS (Geographical Information Systems) software is used to produce and utilize data about the earth, often called geospatial data. In this process, you will work with both existing data and processes built into the software. The goal is to get the data into a usable format. You should allow this process to take about an hour. If you have never used GIS software before, we recommend you work on these in the SAND North lab while a librarian is available. Hours are Monday through Friday, 11 a.m. to 5 p.m. library Page 2 of 45 rev: August 2012

3 A. G ET A D IGITAL E LEVATION M ODEL (DEM) 1. Open Mozilla Firefox. (Do NOT use Internet Explorer.) 2. Google the words national map viewer and follow the first link, to the USGS National Map Viewer. It will take you to: and display a map that looks something like this: Note: This map does not respond well to clicking rapidly. When zooming, panning, etc. let the map reload before you click again. 3. Firefox may ask you if you want to allow pop- ups. You DO want to allow pop- ups from this website. library Page 3 of 45 rev: August 2012

4 4. Use the zoom tool to draw a box around your area of interest. You can also use the sliding zoom tool in the upper left hand corner of the map screen to zoom in and out at more regular intervals. 5. Think carefully about how big an area you want contours for. You may be tempted to choose a much larger area than you need in case you decide to use it later, but a larger area means less resolution, so keep the file size reasonable. 6. If you choose a large area for a location that has a large change in elevation, and you want a small interval for your contours, you will have many contour lines. You can adjust this either by using a larger interval for the contour lines, or choosing a smaller area. library Page 4 of 45 rev: August 2012

5 7. Once you are zoomed in to your desired extent, you are ready to begin the process of downloading your data. Click on the Download Data arrow near the top of your screen. Note: This is clearly not engineering- grade elevation data. library Page 5 of 45 rev: August 2012

6 8. After clicking Download Data, small Download Data window will appear. Click on the link at the bottom of the window that says Click here to download by current map extent. library Page 6 of 45 rev: August 2012

7 9. A USGS Available Data window will appear. To get elevation data for ArcGIS, check the box to the left of the Elevation link. In the pull down menu to the right of the Elevation link, choose ArcGrid. Click Next when you are finished. 10. After clicking Next, a window will appear showing the relevant data available for download. Note the different types of data available. There are both staged and dynamic types. Staged gives you pre- defined areas of elevation data. This downloads faster, but if your area of interest covers multiple staged areas, you will have to spend time stitching them together later. The dynamic type will take longer to download, but it will also give you a single chunk of data that is the size of the extent of the area you selected. 11. Also note that you can choose the elevation resolution of the data you download. A resolution of 1/3 arc second will be more detailed and is recommended for images of smaller areas. A resolution of 1 arc second is recommended for a download of a larger area. library Page 7 of 45 rev: August 2012

8 12. For this example, I will choose to download the dynamic National Elevation Dataset with a resolution of 1/3 arc second. Check the box to the left of your chosen download, then click Next. Note: The area of the map that you will be downloading becomes highlighted in the background. library Page 8 of 45 rev: August 2012

9 13. The USGS National Map Viewer uses a cart checkout system to download its data. This has the advantage of allowing you to download multiple items at once. This information is located under the Cart tab on the left side of the screen. When you have all the data you want to download, click the Checkout button. library Page 9 of 45 rev: August 2012

10 14. The data files will be ed directly to you. Enter your address into the required fields (It will ask you to re- enter your address to prevent errors) and click the Place Order button. library Page 10 of 45 rev: August 2012

11 15. A message will display confirming that your downloads have been ed to you. It may take a few minutes for the downloads to process. Note: sometimes you will also get a message saying that the process has timed out. Check your even if you do get this message, because the data will most likely still send. 16. Check your . You should receive an from the National Map Viewer containing a summary of your downloads as well as links to the actual data. library Page 11 of 45 rev: August 2012

12 17. You will see a window like this: library Page 12 of 45 rev: August 2012

13 18. Depending on the time of day, this could take one minute or 30. Be patient. Eventually, you will be asked to save or open a zip file with a name made of numbers and/or letters. 19. Save the file, then double click on it from the Downloads (Ctrl+J) stored in Firefox. 20. If you lose track of where your file was saved, go to back to Firefox, and from the menu select Tools Downloads (or press Ctrl+J). 21. You will see this: 22. There are many ways to extract compressed files. The easiest in Windows XP/Vista/7 is to drag the files/folder to another location, which automatically unzips it. * You cannot use these files while they are still compressed (zipped). library Page 13 of 45 rev: August 2012

14 23. You need to set up a folder/workspace somewhere. This can be the Desktop, your flash drive, your IFS space whichever you prefer. These directions assume you are using a folder on the Desktop called contours. You will be creating a number of intermediate files before you make your final.dwg, so you should be careful to put them all into this folder so you can go back to a step in the process later if you need to. Create a folder on the Desktop and name it contours. Be sure to drag or decompress your downloaded file into this folder. library Page 14 of 45 rev: August 2012

15 B. OPEN ARCMAP, LOAD THE DEM INTO IT 1. In the SAND North lab, ArcMap is under Urban Planning Applications ArcGIS ArcMap. Launch it. If you are not in the SAND North lab, go to the Start menu and browse through all programs to find ArcMap. 2. Click OK in the start- up dialog box to open a new blank map. Note: If you wish to change your default geodatabase (where intermediate data from processing is stored), you may do so from the pull down menu at the bottom of the Getting Started window. library Page 15 of 45 rev: August 2012

16 3. Click the Add Data button. 4. This time only, you need to set up a shortcut to your workspace - - a quirk of this software - - by clicking the Connect to Folder button (a black plus sign over a yellow folder). library Page 16 of 45 rev: August 2012

17 5. Find your contours folder on your desktop. Select it and click OK. 6. You should see one folder in contours that has a name made up of letters or numbers. library Page 17 of 45 rev: August 2012

18 7. Click through the numbered/lettered folder to the next one, and select the file with the same name and the grid icon (signifies raster data). 8. Click Add. Your data should load into the empty map. library Page 18 of 45 rev: August 2012

19 9. If you are asked if you want to create pyramids, select No these will only take up more memory, and are not strictly necessary. 10. Let s add some context so we can understand where this is in space. Click again on the arrow to the right of the Add Data button and choose Add Basemap from the pull- down menu. This opens a window with a list of backdrop layers. 11. Choose a base map from the ones provided. For this example, I will choose Bing Maps Road. library Page 19 of 45 rev: August 2012

20 12. This will take a few minutes, and should overlay an aerial image on top of your DEM (digital elevation model). You can turn off the Bing imagery layer and turn on the roads layer, if that s more helpful to you. The road names will look slightly squashed if you do this, but we will fix that later. 13. Note that the basemap is not strictly data it s really just a picture of some data, but it is useful in this context. If you want roads in CAD format to accompany your contours, you will need to get them from another data provider. 14. Go back to ArcMap. You should see a picture of streets and other map features: 15. Click and hold the name of your DEM file (the file that you downloaded from the USGS website) and drag it above the Bing Maps Road layer so it overlays the street map. 16. Zoom out a bit, and notice how the DEM lines up with other information on the map. library Page 20 of 45 rev: August 2012

21 C. CONVERT Z VALUES TO FEET Our DEM came from the USGS, a scientific data producer and provider. Because of that, our elevations are in meters. To change them to feet: 1. Click on the Search tab in the right margin of ArcMap. This will expand the search menu, which you can dock to the window by clicking on the pushpin symbol at the top. When the pushpin faces downward, the menu is docked to the screen. library Page 21 of 45 rev: August 2012

22 2. Note: If the search tab is not visible on the side of the window, you can click the search button at the top of the toolbar. 3. Type Raster Calculator into the search bar and press enter. Your first search result should say Raster Calculator (Spatial Analyst) with a hammer next to it indicating that it is a tool. Click on it. library Page 22 of 45 rev: August 2012

23 Note: If you get an error message after clicking on the tool, go to Customize Extensions on the menu, and check the boxes next to 3D Analyst and Spatial Analyst. Closing the window will save your settings. In the raster calculator, you are going to create an expression. Double click the name of the raster layer in this case to add it to your formula, then click the * button or type it in, then type in the conversion for meters to feet: Your final result should look like this: [ ] * Click OK. library Page 23 of 45 rev: August 2012

24 This creates a new temporary layer in our map notice that we didn t specify a filename! This is called rastercalc by ArcMap. library Page 24 of 45 rev: August 2012

25 D. SMOOTH THE DEM DEMs are grids of pixels. When you convert from this square data representation to lines, you may get jagged lines that are an artifact of the data type rather than the information the data represents. To prevent this from happening, you must smooth the DEM before building contours. Go back to the search window and search for Focal Statistics. Click on the tool Focal Statistics (Spatial Analyst). If you get an error when you double click the tool, go to the menu and choose Tools Extensions and check off Spatial Analyst and 3D Analyst and then close the window. (Some tools are not part of the base software package, and need to be enabled.) Drag the layer called rastercalc from the left pane into the Input raster field or click the drop down arrow and select it from the menu. library Page 25 of 45 rev: August 2012

26 For the Output raster, click on the open folder icon and navigate to your workspace you can use the drop- down menu to see a list of workspaces. You want to save this to your contours file which is on your Desktop. Once at your location, create a filename and enter it in the name box (e.g., smoothed). Select Circle from the drop- down next to Neighborhood and set the smoothing radius to 2. Leave the other default settings (i.e. MEAN as the Statistics type) as they are: Click OK. A dialog box will run, and your new DEM will be created. If necessary, close the processing window once it says Completed. You can uncheck and recheck the smoothed file to toggle its display, if you want to compare it to the original DEM underneath it. Right click on the layer called rastercalc in the pane on the left and Remove it. Also remove the original DEM you started with, which is usually named something random with numbers and letters. library Page 26 of 45 rev: August 2012

27 E. CREATE CONTOUR LINES In the Search box, type Contour, click on Contour (Spatial Analyst) NOT Contour (3D Analyst). Make sure your input surface is the smoothed file. In the contour interval field, enter 10, which creates contour lines spaced every 10 feet in height. library Page 27 of 45 rev: August 2012

28 Make sure you are saving your new file in your working folder. The default setting is NOT your working folder; even if it is, you should double- check to make sure you aren t going to lose your new file. Arc uses the same units that are used by your DEM. Leave the default values for the other options. library Page 28 of 45 rev: August 2012

29 For Output features, choose your workspace and give this file a useful name with the contour interval in the name. Click OK. A dialog box will run, and a new shapefile will be created, which you can see in the pane on the left. Shapefiles are a vector GIS file format that can be usually be easily translated to.dwg format. Your output should look something like this: Repeat the above process if necessary by going back to Step 1 of section E. Change the value for the Contour Interval, remembering to give your file a name that describes the contour interval (e.g. contour10ft, contour50ft, 50ftcontour, etc). library Page 29 of 45 rev: August 2012

30 F. CONVERT XS AND YS TO FEET The data we got is by default in a 2D format that uses a unit called decimal degrees for the Xs and Ys. We would obviously prefer a linear unit, probably feet or meters, depending on what your Zs are. GIS calls this process Projecting, which refers to the projection of the 3D earth onto a 2D surface, and the various parameters by which that is done. 1. Go back to the search window, and type Project. Click on the Project (Data Management) tool. library Page 30 of 45 rev: August 2012

31 2. This will bring up a dialog box called Project with many empty fields: 3. Drag and drop your preferred contours file from the left pane into the Input Dataset field or use the drop down menu to select the files. 4. Notice that it populates the Input Coordinate System automatically with the map projection to be used. 5. For the Output Dataset or Feature Class field, ArcMap suggests a filename, (a good suggestion), adding _Project to the end of your filename. library Page 31 of 45 rev: August 2012

32 6. Here is where it gets tricky! You should pick an Output Coordinate System that is good for your area of interest, which varies by state and part of state. We re going to go with the State Plane group of coordinate systems, and you ll select one that works for the part of the state your site is in. After clicking on the button to pull up a separate dialog box called Spatial Reference Properties, click the Select button, then go through the folders Projected Coordinate Systems State Plane NAD 1983 (US Feet) (Alternatively, you can choose plain NAD 1983 if you want your Xs and Ys in meters) library Page 32 of 45 rev: August 2012

33 7. You are now at an alphabetical listing by state. Scroll to the right until you find your state. For some locations within states, it is obvious which one to pick, e.g., this example is for northern Michigan, so I chose Michigan North: library Page 33 of 45 rev: August 2012

34 Note: Some states just use numbers, e.g. California has 6 zones for state plane. A helpful website for determining which state plane system your site is in is at: 8. Notice that your linear unit is now Feet, and click OK. library Page 34 of 45 rev: August 2012

35 9. Click OK again. A new file has been created, and your new lines will not look any different, though they will be in a different color! library Page 35 of 45 rev: August 2012

36 Note: The underlying canvas on which this file is being displayed is still using the old system, which is fine. When we convert to CAD, we use the shapefile that has a correct definition of itself in space, using feet for Xs and Ys. If we want to see a preview of the vector geometry in GIS and how it will really appear in CAD, you can change the map canvas to match the projection of our new file. 10. Right- click on Layers in the left pane and select the last option, Properties. library Page 36 of 45 rev: August 2012

37 11. Go to the tab called Coordinate Systems and select Import on the right- hand side of the dialog box. 12. Find the file you just made a few minutes ago that probably ended in the name _Project. That is your correctly projected contours in an appropriate state plane system. Click Add, or double- click the filename to add it. library Page 37 of 45 rev: August 2012

38 13. This takes the projection definition of this file and adds it to the list of projections on this data frame. library Page 38 of 45 rev: August 2012

39 Move the window out of the way of our map, and click OK while looking at the map. If you get a Warning, just click Yes. Notice that it really changed the proportion of things! (For some more central states in the US, this will be less dramatic.) library Page 39 of 45 rev: August 2012

40 BEFORE AFTER library Page 40 of 45 rev: August 2012

41 G. CONVERT YOUR CONTOUR LINES TO 3D 1. In the search box, type in Features to 3D. Click on Feature to 3D by Attribute (3D Analyst). 2. In the dialog box, make sure your Input features are your projected, best contours (the one that defaulted to the name with the _Project). 3. For the height field, choose the CONTOUR field from the drop- down menu. 4. Also change the Output features file name to something of your choosing (e.g. contours_project_3d). library Page 41 of 45 rev: August 2012

42 5. Click OK. A new file will be made that is explicitly three- dimensional, although we can t really tell in this two- dimensional program. 6. To add reference data such as roads, bodies of water, or something else to help you align this in space with other information in CAD, Rhino, etc., we will help you in the lab. The process of finding such information can be hard, but the conversion is usually easier than what you just went through. library Page 42 of 45 rev: August 2012

43 H. EXPORT TO CAD FORMAT 1. In the search box, type in Export to CAD. Click on the tool Export to CAD (Conversion). 2. Drag your final, 3D cropped contour line shapefile as the input feature. Change the Output Type if necessary, but the default works well. Choose a name for the Output File and click OK. library Page 43 of 45 rev: August 2012

44 Notice that you can add multiple files to this box. If you had streets data or other useful vector data, these would all be in one DWG together, correctly referenced in space, as separate layers. 3. Test your file in CAD or Rhino. library Page 44 of 45 rev: August 2012

45 Note: This example uses a fairly steep site in Houghton, Michigan. Your site may be much less sloped, and you may have to zoom in a fair bit to see the stacked contour lines. library Page 45 of 45 rev: August 2012