Define a Warp File Interactively

The interactive method of defining a warp file is used when you want to use the mouse to quickly warp a grid or image without having to specify coordinates for each control point.

1. Display the image you want to warp in a map by selecting Grid and Image > Display on Map > Grid from the menu bar.

2. From the Coordinates > Georeferencing menu, select the Define a Warp option. The Define a Warp dialog is displayed.

3. Specify an output warp file name (.wrp) and select the warp type you want to use to define the warp (i.e., number of control points (up to 4) or multi-point). Then, select the definition mode as "Interactive". Click OK.

4. The Map Projection question box is displayed with the message: "Define the output coordinate projection?"

5. If you know the coordinate system, click the Yes button; otherwise, click the No button. See the Coordinate Systems topic for more information on defining map projections. The Define Warp Control Points informational box is displayed with a message instructing you to define the old location and new location for each control point. Click OK to continue.

6. Click the left-mouse button on the location of the first control point (where the control point currently is). To ensure that your control point locations are precise, choose locations that use intersecting lines or meridians.

7. Move the mouse to where you want the new location of the control point to be. Click the left-mouse button to define the location of the new control point.

8. If you need to zoom in or pan the map, click the right-mouse button and select the function from the popup list.

8. Specify the location and coordinate values for the remaining control points.

9. An alternative to clicking the last control point with the left-mouse button is to click the right-mouse button and select Done.

9. Now that you have defined a warp file, on the Project menu,  select the Edit a File option to view the warp file coordinates in a text editor.