Alternate Point Files
Alternate Point Files
Alternate Points File
dialogue box allows the user to define the point mapping in one image and use it in another. At
first glance this might seem a useless exercise but there are a couple of situations where it can be
- One is the situation where you are forced to add targets to an object in order to have easily
identifiable points on the image but you do not want these targets in your rectified image. In this
case you can set your camera on a tripod and take one photograph with the targets and another
You can then rectify the targeted image and save it then open the presentation photograph and
rectify it to the same parameters.
the position and focal length of the camera cannot change between photographs
but the ability to alter the exposure and to add or remove filters greatly increases your ability to
ensure that your measured points are easily identifiable in at least one photo while the features in
which you are actually interested are properly rendered in another.
- Another situation is when you want to use the points you mapped to a current photograph
to another photo of the same object you found in the archives.
(see example 1 below).
When you do this the points imported will not be correct in the second photograph but you can
move them into position with the mouse and you won't have to reenter the coordinates.
If the image in which you mapped the points is larger than the one into which you want use
them you may get a
Points out of range
warning in which case you may have to zoom out considerably to find
these points so you can move them into position on the image.
Some uses of this feature include:
- Using one set of point coordinates to rectify several images of the same object.
For example if you have several photographs of a surface taken at different times you can
measure and rectify one of these images then load a second one, select the point file of the first
and then move the points into the correct positions on the new photo.
- Using points from a photo containing targets or a grid to rectify a photo with the targets
of course the photo must be identical in terms of camera location, direction and focal length
- Using points from an adjacent rectification when making a collage. Saves reentering
- You will also use this dialogue box a lot as you work your way through the
Generated by: CART
(Thu Sep 20 17:56:25 2007