How can I distort the shape of a PDF

[Bob658]

I have a raster PDF that i need to distort to fit into a trapezium shape. Does anyone have any ideas how i could do this? 

[steven-g]

A before and after sketch might help, turning the pdf into a block will let you scale x or y independantly (rotating the pdf first before creating a block,  would let you create a parallelogram).

But a trapezoid? Is this an image pdf or geometric

[Bob658]

Not sure how clear this is but I'm trying to get the frame on the pdf to fit to the redline (which is rectangular). I have tried creating a block with the pdf at an angle but the distortion in the pdf is in not regular. Looking at it again it's not actually trapezium but a scalene quadrilateral. 

 

[eldon]

Is this PDF the original sent by the Land Registry to the owners, or is it a photocopy?

 

You cannot take accurate dimensions from such plans.

 

With your current problem, why not take the redline such that it is totally within the frame?

[Bob658]

It's a photocopy of a photocopy which has then been scanned. I appreciate the plan is no longer accurate but the client wants me to overlay it onto a site layout to see if he has any issues. I have a digital CAD model of part of the housing housing area which I intend to use locate the plan once I've managed to get as square as possible. I know I can download a new pdf from the Land Registry (assuming the land has been registered) but i get asked  for this on just about every site and every time I'm given a sh*ty photocopy or scan to work with. There must be a way of mapping the pdf to an area and manipulating it by moving the edges or intersections. Basically I want to paste it onto a stretch armstrong and pull it around.

 

[eldon]

The old Land Registry plans used to have grid lines on them, so you had half a chance to scale things nearly so. I usually take a screen snip of Land Registry plans to make a png image, which is easier for me to place (my version of AutoCAD does not handle PDFs !!!!!).

If you compare Ordnance Survey data with a modern topographic survey, usually there are no common points, and the best one can achieve is a best fit, which lines up some of the  points. I use Align, using two points. One can then see gross errors when comparing.

If you can devise a way to 'manipulate' the PDF, then you will be doing all the boundary surveyors out of a job! Ordnance Survey mapping was mostly done in the days before electronic distance measuring and GPS, and was mapped for use on paper mapping. Now it is being used for determining millimetres, which it was never set up to do.

I wonder why the plans usually do not show a scale bar.

[BIGAL]

You will find the maps are "rubber mapped" in that they are produced as a best fit to a series of points, the larger the area the worse the errors, we use aerial photos every day and at big scale will find all sorts of errors, but you must remember the earth is not flat but has a radius. The maps are getting better. Our surveyors would apply what is known as a scale factor and this varies depending on where you are in the world and is to do with flat versus curved. GPS is curved a total station survey is a series of facets not to mention the curvature of the measuring beam. Like the others Align is about the simplest way to go.  

[steven-g]

Given the comments above, I would also doubt any change would be valuable, other than visually pleasing, but what you want to do is probably more suited to an image editing program like photoshop, or gimp a free program that also has various tools for transforming objects, you will want to look at things like "skew" and "shear"