This menu allows selection of the type of mapping function to be used for the permanent reference points. When selecting the type of mapping, the user should note that the mechanics of the video image mean that, unless there is a relative movement between the video camera and aparatus, the vertical coordinate should at worst suffer only a simple translation. In contrast, the horizontal coordinate may undergo a much wider range of distortions, particularly if the image is being captured from a freeze frame of a video recorder.
0 This option suppresses the mapping by substituting an identity transformation.
1 This is the simpleset of all mappings, consisting of just simple translation. Despite its simplicity, it will generally be the most appropriate form of mapping. This option differs from [2 ..] in that the vertical displacement is constrained to be an even multiple of lines. This is appropriate if the video camera is mounted rigidly relative to the experiment: any vertical displacement of the image is due to a difference in timing of the vertical sync pulse, but the first field must still occupy the even lines.
.] in that it offers a simple translation, but in this case the vertical displacemnt of the image may be any fraction or multiple of a line. This may be appropriate when there is some vibration in the system.
3 General purpose mapping when there may be some general changes between the video camera and target. The mapping allows for simple linear distortions (rotation, translation, shear).
4 General purpose mapping where there may be a more complex change between video camera and target. The mapping allows for afine (simple nonlinear) transformations in addition to linear transformations.
The vertical (i) coordinate may be translated and stretched, whereas horizontal may have a more complex nonlinear distortion.
6 This mapping function is designed as an extension to type 2 but offering the ability to correct for small rotations of the field of view.