Select Point Tool - The
Select Point tool is used to select and drag register points to a location
on the map for which real coordinates are known so that they can be entered
in the corresponding XY edit fields.When an image is opened that is not geo-referenced, or if the image is not mapping to the correct coordinates, it can be registered or geo-referenced again. The Register dialog is brought up automatically when you import an image that is not geo-referenced, and can be brought up by right clicking on the image in the project explorer and choosing Register.
When SMS opens an image, it looks for geo-referencing information in the image. If the image is not self-referenced, SMS looks for a world file with the same name as the image (.wld or .jpgw extension). If neither of these is found, the register dialog is invoked.
Before an image can be used for background display or for texture mapping, the image must be "registered". Registering an image involves identifying three points on the image corresponding to locations with known real world (XY) coordinates. Once these points are identified, they are used by SMS to stretch or map the image to the proper location when it is drawn with the other objects in SMS in the Graphics Window. If an image is not registered properly, any objects which are created using the background image as a guide will have the wrong coordinates.
An image is registered using the Register Image dialog. The main feature of the Register Image dialog is a large window in which the image is displayed. Two or three points (shown by "+" symbols) are also displayed in the window. These points are used to identify locations with known real world coordinates. The real world coordinates (X,Y) and image coordinates (U,V) of the registration points are listed in edit fields below the image. The points are moved to the desired locations on the image by dragging the points using the tools to the left of the image (described below). Once the points are located, the real world coordinates can be entered in the edit fields shown below the image.
The options include:
2 point or 3 point registration - The user can register an image with 2 or 3 points. 2 point registration rotates and uniformly scales an image. 3 point registration allows for non-uniform scaling to account for some parallax.
Select Point Tool - The
Select Point tool is used to select and drag register points to a location
on the map for which real coordinates are known so that they can be entered
in the corresponding XY edit fields.
Zoom Tool - In
some cases, it is useful to magnify a portion of the image so that a registration
point can be placed with more accuracy. The Zoom Tool is used to zoom
in a portion of the image.
Pan Tool - After
zooming in on a portion of the image, the Pan Tool is used to pan the
image vertically or horizontally.
Frame Macro - The
Frame Macro is used to automatically center the entire image within the
drawing window of the dialog after panning and zooming in on a specific
location.
Import World File - This option allows the user to import a TIFF world file (.tfw). A TIFF world file has the information needed to set the (X,Y) and (U,V) coordinates in order to place the image in the correct world coordinates.
Image name- This allows the user to associate a name with the file. This name will appear in the project explorer.