Overview: Students download a section of a topographic map of their community from the ATEP website. This file will overlay the Google Earth satellite imagery. Students use the path tool to trace a contour line on the topographic map, then turn off the topographic map to see the contours on the satellite imagery. Afterwards, students add a contour line of tsunami inundations using elevations from Google Earth. Objectives: The student will: download a KMZ file from the ATEP website; use the path tool to trace a contour line; and turn Places on and off. Materials: Computer with Internet access and Google Earth installed. STUDENT WORKSHEET: Whole Picture: The elevation model that Google Earth uses for Alaska is low resolution; as a result it is not very accurate. For example, it is quite possible to be on the ocean and still have an elevation reading of 10 meters in Google Earth. GPS elevations are based on a mathematical model of Earth, and these elevations are not completely reliable either. Consequently, mapping the tsunami inundation contour will only give a rough idea of the where the ocean actually reached. Activity Preparation: 1. Before beginning this lesson review topographic maps and contour lines with students, if necessary. 2. If students have not already done so, they should download the satellite imagery of their community from the ATEP website before they add the topographic map. In many cases this imagery is more recent than what Google Earth has available. However, because Google updates its imagery regularly, that may not be the case for your particular community. 3. To make a contour line of past tsunami inundations, the rise above sea level needs to be known. Tsunami inundation data for communities in Alaska can be searched for on the NOAA/WDC Historical Tsunami Database at National Geophysical Data Center website. The address is http://www.ngdc. noaa.gov/hazard/tsu.shtml. Click on Global Tsunami Database then select Tsunami Runup Search. From the Tsunami Runup location drop down menu choose Alaska then submit the search. The Max Water Height (inundation) values given are in meters. If necessary, set the elevation in Google Earth preferences to meters. If your community has not been inundated by a tsunami or the inundation is less than one meter, select a different community such as Kodiak (6.89 meter Max Water Height in 1964) to use with the lesson. If there is more than one runup for your community use the one with the highest Max Water Height. Activity Procedure: Distribute the STUDENT WORKSHEET: and guide students through each of the steps. ATEP 2006-2009 UAF Geophysical Institute 1 GIT:
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Student Worksheet (page 1 of 5) Directions Overlaying a Topographic Map in Google Earth Launch Google Earth and navigate to your community. Launch a web browser, and download the topographic map of your community from the ATEP website at http://www.aktsunami.com/student_resources/resources_topomaps.html In the Google Earth menu, open the topographic KMZ file that was downloaded. The map will appear as an overlay in Google Earth. You can use the navigation tools to tilt and zoom in. Zoom in to the topographic map to find the lowest contour line above sea level. A contour line is a brown line that represents elevation. Depending on the community the contour lines may be from 20 feet to 100 feet intervals. Tracing contour lines STEP 1. Click on the Add Path tool from the Google Earth toolbar or from the menu go to Add à Path. Add Path STEP 2. Type a descriptive name for the path such as 100 ft. contour line. ATEP 2006-2009 UAF Geophysical Institute 3 GIT:
Student Worksheet (page 2 of 5) STEP 3. Click on Style, Color, change the color to red, and increase the line size to at least 1.5. STEP 4. Using the mouse and pointer box click to place points along a contour line. (See below for how to edit the path). Pointer How to Edit the Path To move a point use the mouse and finger pointer to reposition a point on the path. To add a new point just click on the path. To delete a point right-click (PC) or ctrl-click (Mac) on the point. ATEP 2006-2009 UAF Geophysical Institute 4 GIT:
Student Worksheet (page 3 of 5) Saving the Path Once the path is saved, it cannot be edited. Make sure all corrections are done before saving. STEP 5. Right click (PC) or ctrl click (Mac) on the Path name in Places, under Temporary Places, and select Save Place As, and Save as a KMZ file. Seeing the contour line in the satellite imagery STEP 6. In the Places sidebar uncheck the topo map layer. The red contour line will appear on the satellite imagery. If desired, a Placemark could be made on the contour line that describes its elevation (i.e. 100 feet elevation contour) by clicking on the yellow pin. Adding Tsunami Inundation Contours Your teacher will provide you the with sea level rise of past tsunamis for your community. In this part of the activity, the elevation data in Google Earth will be used. (NOTE: The elevation Google Earth uses is likely to be off from true elevations, especially in Alaska.) The contour line will only be an approximation. STEP 7. Navigate to your community in Google Earth. STEP 8. The topo map layer should still be unchecked, so it is not visible. STEP 9. Click the Add Path button from the toolbar. Give the layer a descriptive name and change the color to a blue, following the steps above (STEPS 1 3). ATEP 2006-2009 UAF Geophysical Institute 5 GIT:
Student Worksheet (page 4 of 5) STEP 10. With the pointer move to a location in the image that is at the same elevation as the sea level rise was during the tsunami. The elevation is given at the bottom of the Google Earth window, in the center. In the Kodiak example at right, 7 meters is pictured. Elevation in Meters Continue adding points to the path at the same elevation. When finished click OK and save the file as a KMZ file. Putting It All Together Click on the Placemark layer that you made of emergency services from the Placemarks in Google Earth lesson, past tsunami inundation levels, and contour lines in your community. You should see where past tsunamis have been, and where emergency services are located, all in relation to elevation in your community. 1. Is the runway above or below the high water level of a past tsunami? 2. Are there any emergency services below the high water level of a past tsunami? If so, list them. ATEP 2006-2009 UAF Geophysical Institute 6 GIT:
Student Worksheet (page 5 of 5) 3. Are there any homes below the high water level of a past tsunami? 4. What is the elevation of your school using the topographic map contour lines? 5. What is the elevation of your school using Google Earth s elevation? 6. Is the location of the school in a tsunami hazard zone? ATEP 2006-2009 UAF Geophysical Institute 7 GIT: