Roger Broadie wrote:
Hello Paul,
I thought your panorama was pretty good, but I don’t think you have fully
overcome the problems of parallax resulting from creases and folds. The main
cause, I suspect, is the camera tilt of 6 deg plus or minus from the vertical
that the pitch values of the optimiser imply.
I think that 3D items can cause trouble, even if the camera is shooting
perfectly vertical. While the camera may be perfectly
vertical w.r.t item directly beneath it, it is (of course) at an angle to items
at the edge of its FOV. When the camera
is translated in X,Y, (possibly Z), the item is now at a different point in the
new FOV.
Diagram attached.
So while I would not normally expect to include the Plane Yaw and Pitch
parameters in a truly planar photomosaic, it did seem worth trying them here.
They do seem to help.
Yes - if the map is NOT a true plane, but compose of multiple planes (or at
least may be thought of as such)
the sub-plane parameters may help, at least "on average".
I attach panoa.pto, based on your file, which takes that approach and also
includes some tuning of the control points and fuller lens optimisation. But I
hung on to the h and v points, because I think they are one of Hugin’s
strengths. I have resolved some remaining glitches, either with added control
points – automatic control point finders seem to find otherwise featureless
areas of grid-lines difficult to deal with – or with masking, but have not
tried fully to resolve problems with the
grid-square P25, where the different shapes of the square as captured in e.g.
images 17 and 23 illustrate graphically the problems of the parallax present in
places in your images. The end result yields an average error of 1.2 pixels
and a maximum of 3.2, for a panorama matching that of pano.pto in size.
Thanks for the observation - I'll go look!
Broadly, I agree with Terry Duell (Wed, 27 May 2015 at 10:13:42 +1000) that the
mosaic mode is working OK. He has given us a pto file (Wed, 27 May 2015 at
12:34:56 +1000) that does not use the Plane Yaw and Pitch parameters. It has
an error of 0.5 average and 2.9 maximum, but is for a panorama of only about
half the width of yours. Still pretty good, though, even at the full size.
Agreed - thank for you effort and thoughts.
My problem of how to best capture a 1816 map remains, of course. :-)
BugBear
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