1. ArcGIS 9 ch 3 Edited 10/24/05 1 Sometimes, the data that you receive is not as accurate as it could be. You can easily correct this problem by making some simple adjustments in the data. This next lesson is designed to take you through these steps so that you will be able to make these changes as needed. Editing Spatial Data

2. ArcGIS 9 ch 3 Edited 10/24/05 2 Notice that some of the streets in the view above do not line up with the aerial photo. Let’s edit the street data so that they overlay the image correctly. (The image is more accurate than the street layer. Therefore you will be moving the street layer to fit the image.)

3. ArcGIS 9 ch 3 Edited 10/24/05 3 1. Before you can edit features, you must make the Editor tool bar active. Click on the button that looks like a pencil connecting four points. The Editor tool bar will appear. It may be in a different location than you see in the example. Arc9 allows you to dock and undock toolbars to fit your preference.

4. ArcGIS 9 ch 3 Edited 10/24/05 4 4. In this example, the name of our data set ends in “lka.” In the target drop-down make sure the you are editing the feature class ending in “lka.” 2. To edit a feature, click on the editor drop-down on the tool bar. Then select “Start Editing.” 3. You may get a message referring to editing in a different coordinate system. Go ahead and click “Start Editing.”

5. ArcGIS 9 ch 3 Edited 10/24/05 5 5. Select “Modify Feature.” Then click the arrow to the left. 6. Turn off the county boundary layer by “clicking off” the check mark in the layer that ends in “cty00.” Otherwise it is easy to accidentally edit the wrong data.

6. ArcGIS 9 ch 3 Edited 10/24/05 6 7. With your mouse, click and drag the “handle,” (red square) vertex of the line and move it to the position desired. 8. Continue moving each vertex so that the street features at your school are properly overlaying the streets on the aerial image. 9. When you have finished, go back to the “Editor” menu and select “Stop Editing.” Save your edits.

7. ArcGIS 9 ch 3 Edited 10/24/05 7 10. If you are moving roads at an intersection you will want all of your roads to come together at a single point – not like you see here in this picture. 11. To make the end point of the roads (called nodes) come together, you will use an editing feature called snapping. Go to your editor button and hold it down.

8. ArcGIS 9 ch 3 Edited 10/24/05 8 12. A box similar to the one on the left will appear. Check the box under vertex for the layers you intend to edit. 13. Now when you move the nodes close to each other they will snap together.

9. ArcGIS 9 ch 3 Edited 10/24/05 9 At times, you need to edit existing data. Other times, you need to collect our own. Using a GPS is a common way to collect data, but is impractical in some situations. “Heads-up” digitizing an effective substitute for GPS that uses aerial photos and your GIS to produce the desired features. The next chapter will show you how to digitize your own data in class and use these features in your project.