When you open a raster file you need to register it to identify coordinate point references for the image. Using a vector map as a reference, you identify the coordinates of the vector map and match them with equivalent points on the raster image. This coordinate information allows MapInfo Pro to determine the position, scale and rotation of the image so that you can overlay vector data on top of the image. The coordinate information is stored in a TAB file created during the registration process. The TAB file enables you to re-open the raster file in MapInfo Pro format.
You usually register the image the first time you open it. However, you do not need to register the image if you do not plan to use vector data with it, or if it already contains georegistration information.
Raster images usually fall into one of three categories:
- A fully registered image, containing control points and a projection (for example, GeoTIFF file).
- A partially registered image containing control points, but missing a projection (for example, an image with an associated World file).
- An unregistered image missing control points and a projection.
Once the image is registered, opening it again requires a slightly different procedure. Opening both unregistered and registered images is explained in the next section.