Overlay analysis is one of the key tasks made possible using Geographic Information Systems Technologies.

We will learn this principal by creating layers using the community maps you have drawn during program and Google Earth software.

Your maps have been converted into TIFF files by scanning the original documents.

The goal of this lesson is to provide you with an understanding of electronic processes associated with creating, editing and adding overlays to an existing spatial data set. In this case, the existing dataset is derived from satellite images that are available through Google Earth. The overlays will be created from the community maps you have already created.

Materials

Electronic version of community map, TIFF file format, stored on Classroom CD

Computer

Google Earth Software

Notebooks and Pencil

Procedure

1. Open Google Earth on your computer workstation.

2.     Use the Add command to create a New Folder and Label it Student Work – MY Name (insert your first name). Save the folder under “Temporary Places.” This menu is found on the left-hand side of your screen.

3.     Use the Fly To command to locate the area that matches the location depicted in your community map. Frame what appears in the screen to match as closely as possible the area that you depicted on your map.

4.    Place the Classroom CD in the CD Drive of the computer.

5.     Use the Add command to create an image overlay. In the first box, name your layer. Use the Browse tool to select your map from the CD you have placed in the CD Drive. Select your map and click OPEN.

Notice that the map appears on the screen. Adjust the position of the map, stretch and rotate the map and set the opaqueness level until it matches as closely as possible the area shown in the satellite image. Write a description of your map in the sescription box that appears on your screen. Save your map when complete.

6.     Use the Add command to enter 4 placemarks onto your map. The placemarks should identify locations or landmarks of significance in your community. Write a short description of why you think each place is important in the description box. Save each placemark in your Student Work folder.

Discussion Questions

1. How well does your community map layer correspond to the boundaries of the Google Earth Image layer?

2. Explain a procedure that would allow you to create a layer that matches the scale of the Google Earth layer.

3. What information does your map provide that is similar to the landuse information found in the Google Earth layer? What information does your map show that is not found on the Google Earth layer?

4. Write two questions about the location you mapped that you have based on the overlay that you created. Describe how you might answer each question based on the use of overlays.

Lesson Three