On Feb 22 2005, Olly Betts wrote: > On Tue, Feb 22, 2005 at 03:48:12PM +0000, Wookey wrote: > > There should be a way for users to make centrelines match to drawings > > > graphically, not having to know the resolution of the scan and > > > re-generate the centreline using a strange scale to make it fit... > > Tunnel seems to do this very well. I *think* it works like this: > > (1) you select a point on the background image and the corresponding > point on you drawing then tell tunnel to translate to make the two > coincide. > > (2) you select the point which matches from (1), and another pair of > corresponding points, then tell tunnel to rotate and scale around > the point in (1) to make the other pair coincide.
This is how tunnel works, it can work quite well, assuming that there is no distortion in the image, i.e. a nice scan rather than photographed, and if there are any loop closures, then the destortions for each loop is calculated the same. In case you want to use the same ordering of clicks, for the rotation and scaling, the first click is where the scan is at the same point as the computer centreline, the secound is on a point on the scan and the third is on the corresponding point on the centre line. The first and last clicks are typically survey stations, so you can tell tunnel to start and finish on them(using snap to node features), so there are no errors due to not quite clicking on the survey stations. Cheers, Martin
