Dimensions on imported PDF are not accurate. Measured a 6 foot line and got 5 1/4". Value not editable

[rnortonKXMDP]

I imported a PDF with grounding plans for a site so I could easily measure and calculate total linear feet of wire but measuring a line that shows as 6' on plan only returns 5 1/4" using DI command.  I tried to change length in properties but is not editable, just gives me a calculator.  Also tried SC command hoping to change scale of drawing by changing scale of that same line to be 6'0'' but didn't work (I may be doing incorrectly as I am pretty new to AutoCAD)  Any advice?  I am using AutoCAD 2013

[pendean]

You'll need to share that actual PDF here for others to test: it could have just been created at a on-scale despite what the titleblock may have stated. Or are you just assuming it was created to a scale?

BTW, your screenshot, what is the purpose of that? You just screenshot your post.

[paullimapa · Accepted solution]

Most likely pdf is not to correct scale 

Assuming it’s not stretched with a different scale factor in the length vs width of the pdf sheet you can try and use Scale command select all objects imported and use endpoint of the line as basepoint then enter Reference option. When asked for basepoint again select the same endpoint and then the other endpoint of the line and enter the actual measurement 6’

This should scale all the objects imported with that reference scale. Then measure another object with a known dimension to check if this worked

[baksconstructor]

PDF is not a graphical tool. The dimensions from the PDF will never match when imported. Only approximate. Even if you scale them correctly horizontally, the vertical ones will not be correct. There will be no accuracy when importing PDF.

[tramber]

It happens that some PDFs are more accurate than awful DWGs some people draw.

PDF is a graphical tool. It is not if the drawing is an embedded image... 

When it contains vectors, a good use of the Reference Option together with the PDF Osnap can sometimes give a quite good background.

[cadffm]

Hi,

if tramber replied to you: I am 100% with tramber!

You are talking about some "scans" of paper, but PDF can contain vector data like .dxf/.dwg or any other cad data too

and if so, the content is accurate like in cad (same for .dwf).

[Simon_Weel]

I've never seen a PDF imported without the need to scale it. Scale by reference is my preferred method. Like if you know the length of an element in the PDF, draw a line of that length along the element in the PDF and then use Scale by reference using the PDF element as a reference.

[baksconstructor]

The internal PDF standard is 72 dpi. Coordinates falling between these values are rounded. As a result, a shift occurs. PDF will never be equal to CAD.
Vector PDFs are slang for those who do not know the structure of PDFs.
There is no Vector or any other PDF name, there is only one PDF standard.

[cadffm]

Hi,

>>"The internal PDF standard is 72 dpi."

Is it? okay. But not for CAD, also not for Scans. However.

>>"Coordinates falling between these values are rounded. As a result, a shift occurs"

As it is in CAD formats too. The PDF standard in Acad for example is 600-1200dpi (up to ~4800)

>>"PDF will never be equal to CAD."

You are right, BUT

In the rarest cases, it will. The question is: How accurate is "equal enought" - or not.

Drawed on clean integer coordinates, perfect. If not, but the precision was well selected for this plot: It's "equal enough" for me and my Jobs.

Right, you should not use the imported data to feed a machine that automatically produces a component for a weapon, machine or nuclear power plant,
but otherwise?
I beg you.

Let's say dpi300 (never saw a 72DPI, the standard for drawings in my world is 300-800dpi)

what means it is 50-100x more accurate than my Eyes will detect the difference on paper (in relevant 1:1 scale)

>>"Vector PDFs are slang for those who do not know the structure of PDFs." >>"There is no Vector"

I would actually completely disagree with that, but it wouldn't be effective here, but okay.

Whatever it is, there is a kind of precision, like decimal places for a real.
It's your fault that I bought a book for my vacation.

For others who can't imagine by words only, sample attached for 300 and 4800:

Object data with random coordinates (like in the read world, nit clean integer data),

but created For any kind of building and civil plans, much more than enough,

also if you use 600dpi or just 300, instead of a high quality PDF.

[rnortonKXMDP]

That worked, many thanks!

[paullimapa]

Glad to have helped…cheers!!!