Preserved Topic: distortion from digital map scannings

Hi there, I am urgently need help.

The project I am doing involves scanning historical maps. And my job is to attach every single map together to form the whole city of Sheffield (UK).

The problem is, there is always distortion occured on the edge of every single map. There is a frame for each single map and this frame should be a perfect rectangular shape, but this would never happen.

Is there anyway that I can somehow 'stretch' the scanned map to a perfect rectangle?

Please help me........ Thanks a lot!

David

I'd say post us an image of one of these maps so we can get a better understanding of what the problem is.

I would like to put a map on the net but the file is extremely large. Therefore, I did a simple diagram here.

All I want to do is to adjust the dash line to a perfect rectangle frame.
Anyone can help? I appreciate that deeply.....

David

Are you using a flatbed scanner? I can't imagin it looking all wavy like that on a typical flatbed scanner. I can't think of any way in Photoshop to adjust the edges accurately. I'd think you should just try to keep the map flat on the scanner.

The process is called 'stitching'. There are custom programs out that can stitch multiple scans together seamlessly. I've never used them myself, but I remember reading reviews of scanners that stressed the stitching software as good/bad points of the scanner.
A quick web search turned up: http://www.panavue.com/products/index.htm .

If you have to do it by hand, I have no suggestions, sorry :/

I can't think of any trick in Photoshop to distort (or in this case "undistort") an irregular shape like that. Is it irregular because the antique paper is wavy? Does the live area of the map go right out to the wavy edges? As HS asked, how are you scanning them? One possible suggestion is to have them photographed by some place that specializes in architectural work - some of them might have a copy camera with a vacuum back large eough to accomodate the maps. Then scan the photos. The vacuum back might suck the paper flat enough to get your clean edge.

I know the trustees of historical documents might not go for that, but somehow you have to get a clean flat copy before you can begin stitching the separate images, whether you do that by hand or with software.

The software in the link I posted above supposedly will work with warped images. It apparently distorts the images to merge cleanly.
That's what their promo materials say, anyway. Couldn't hurt to download the free trial.

The technology seems similar to the environment mapping software that's getting popular lately. You take normal (rectangular) photos in all directions, and the software makes a spherical environment map out of them. Pretty sophisticated pixel-pumping, when you realize that there is no normal way to fit 6-10 rectangular images on a sphere, cleanly stitched.

Hi Guys,

Thank you all for the above suggestions. I really appreciate that. ^_^

To answer some of your questions:
1. The size of each historical map is about 40ins by 30 ins (or 100cm by 70cm). Therefore, I can not use A4 or A3 flatbed scanner. Those maps were scanned in a local graphical shop where A0 scanner was used to do the job with a resolution 400 pixels/in.

2. I think the distortion was occured because the original maps were 'wavy'. I thought I can use Photoshop to do the repairing work.

3. More suggestion is very welcome!!

4. Thank you all again..........


David

Maybe try using the shear filter to compensate?