How to stitch a map divided into 32 scans...

[Edward Carnby]

Hi all,

I've used Hugin for some time and I encounter no problem stitching old maps I scanned from libraries. They usually were divided into four or six parts. I have now to stitch a very large map of Italy divided into 32 scans (eight rows, four columns). I followed the tutorial (stitching flat scanned images) but I wasn't able to achieve a decent result. The optimizer always stitch it in a bad way. I tried to stitch some parts and than stitch them again with others but the result was pretty unacceptable because of bad alignment. Besides I have a Win 64 system and cannot install autopano sift C. Hints are appreciated.

Best regards.

[bugbear]

Do the sub-images overlap (like photographs) or do they tessalate edge to edge?

I've done maps both ways, and can advise.

BugBear

[Edward Carnby]

They overlap.

[panostar]

On Friday, December 14, 2018 at 10:25:25 AM UTC, Edward Carnby wrote:

They overlap.

And are all of the images exactly the same size? Crop them if not.  Try pretending that you used a very long focus rectilinear lens, so that the images have a very small HFOV (1 degree or even less).  Then stitch them in the usual way but optimize only y,p,r of all except one image. Scanned images may suffer from shear distortion so you may need to include either the horizontal or vertical shear (not both) parameter in the optimization too.

John

[Edward Carnby]

Thank you!  With your help I was finally able to stitch the images.

Thanks again!

[Abrimaal]

The problem is that there is no rectangular (planar) projection available in Hugin.
It is different from rectilinear.
Rectilinear projection preserves straight lines, but does not preserve straight angles.
Rectangular does not preserve areas, but preserves straight lines and angles.

The adjustment of partial images is based on control points, as always,

but it is done by rotating and resizing images.

Field of view is discarded because scans may have different pixel size and they are not related to any lens field of view.

If you have an Android device, you may try Bimostitch or Mapstitch, that use the planar (rectangular) projection.
Bimostitch is better because it does not blend images (you can select between matching or blending).

For Windows you may try ArcSoft Scan-n-Stitch Deluxe, but it is very limited and outdated.
All images must be the same pixel sizes and it often fails even with 2 rows map, because correction of misplaced control points is not available in this software.

[Bruno Postle]

On 30 January 2019 22:15:56 GMT, Abrimaal wrote:
>The problem is that there is no rectangular (planar) projection
>available in Hugin.
>It is different from rectilinear.
>Rectilinear projection preserves straight lines, but does not preserve straight angles.
>Rectangular does not preserve areas, but preserves straight lines and angles.

So long as you fix yaw and pitch to zero, Hugin is fine with stitching scanned images using rectilinear input projection. This is what the XYZ mosaic parameters are for.

--
Bruno