This icon,
F4
or the
Tools->Output Image Parameters
menu item will bring up the following dialogue box:
It is divided into 4 sections
The first area of this dialogue box deals with the scale of the output image. The first box is read- only and indicates the natural scale factor which is calculated from the size of the image and the distribution of your measured points. This value is not significant, we just need a starting point. The scale is in pixels per real world unit.
The "natural" value will be offered as the default when you first rectify an image but the final scale of the rectified image can (and should) be specified in the second box in this area. Ways to use this feature are as follows:
The second area of this dialogue box has check boxes which will cause the image to be mirrored along either the horizontal or Vertical axises. The usefulness of this feature is less obvious (we put it in for debugging) but it has it's applications. For instance a stained glass window that you photographed from inside (because it shows better) but measured from the exterior (using mullion intersections perhaps) can be integrated into the exterior elevation by rectifying it to the exterior measurements and mirroring in horizontally.
Note: Do not use this option when rectifying for insertion into AutoCAD.
The third section of this dialogue allows for the rotation of the rectified image. This is unlikely to be of much use in the case of 2D coordinate systems but can be very helpful when working in 3D.
Imagine, in the example below it was impossible fo measure the bottom right corner of the cube. (Usually there will be a shrub or a bus in front of important points)
So you measure the closest thing you can see but this will result in a somewhat rotated right face due to the fact that the O & H points are not parallel to the base plane.
The rotation tool can be used to overcome a missed measurement point in a couple of ways:
The wall sample is a real world example of the same problem except here there are no points on any axis.
Using the default O=1 H=2 V=3 you will have to rectify using:
In these cases of inexact rotation angles you can get a pretty good idea of the quality of the result by selecting a vertical or horizontal line, zooming in and scrolling your reference line towards an edge to see if they are parallel.
Note: Do not use this option when rectifying for insertion into AutoCAD.
The final section of the Output Parameters dialogue box deals with the camera distortion parameters you want to use.
The first time you rectify an image the Take from camera descriptor button will be selected and the camera currently defined as the default in the Camera management dialogue box.
If you are revisiting an image you have previously saved the Take from current PTS file option will be selected and the name of the camera used the last time the project was saved will be shown to the right. If there is a camera specified in the PTS file (including the camera "None") those parameters will be used for the next rectification unless you change it.