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Hand drawn plan scanned PDF file scale is incorrect

MS90

Hello, 

Is there a method to scan hand a drawn plan  to PDF and keep the scale correct(as per the original hand drawn scale). I noticed that scanned full size drawings are losing their initial scale (a little off compare to original drawings) .  I usually scale drawings in AutoCAD model space,  this time i just  need to create a duplicate of the hand drawn plan. Any help and advise would be greatly appreciated for this workflow. 

 
Nov 15, 21 3:10 pm

WTF are you talking about?  


Nov 15, 21 3:13 pm  · 
2  · 
MS90

Is my question too confusing for you?

Nov 15, 21 5:33 pm  · 
 · 
joseffischer

your scanner/software/PC setup must be messed up somewhere, it should be scanning exact.

Nov 15, 21 3:18 pm  · 
 · 
JLC-1

never happened, nowhere.

Nov 15, 21 3:35 pm  · 
 · 

Always happened, everywhere I worked. I suppose the scans could be off by 1/256" but at that point it's not noticeable with line thicknesses when scaling.

Hence why you don't scale drawings.  :)

Nov 15, 21 3:53 pm  · 
1  · 
JLC-1

"A little off" is un-fixable, it's the way scanners work, they distort the image because the paper is moving and not always at the same speed/direction - if you scale one axis correctly, the other will be off.

Nov 15, 21 3:35 pm  · 
 · 

Odd. I've never had an issue with scanners like this. Guess ours have always been calibrated correctly.

Nov 15, 21 3:51 pm  · 
 · 
JLC-1

I guess you also don't believe paper has shrinkage and expansion depending on humidity and temp. go scan a 30 yr old set of plans and let me know.

Nov 16, 21 10:33 am  · 
 · 

Oh I know that paper will shrink and expand. Just like I know that a properly calibrated scanner won't be off enough to make a difference. Sure the scan may be off a wee bit - no more that the margin of error that line weights create. Hence why you don't scale drawings.

Nov 16, 21 10:43 am  · 
 · 
citizen

Fortunately, scale and dimensions are just estimates anyway.

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Nov 15, 21 4:47 pm  · 
3  · 
atelier nobody

Funny how we always tell contractors not to scale the drawings, then don't listen to our own advice...

Nov 15, 21 5:48 pm  · 
4  · 

The trick is to scan your scale. Then print it out and use it to measure the PDF.

Nov 15, 21 6:38 pm  · 
6  · 
bowling_ball

Seriously, how hard can this be? Alternatively, scan it, bring it into Photoshop / AutoCAD / Revit/ sketchup / anything that allows you to resize a drawing. Then print. This is assuming the scale is actually off in the first place. I think copiers might resize things slightly but not scanners. Flatbed would be best.

Nov 15, 21 8:15 pm  · 
1  · 
reallynotmyname

Yes, flatbed is the best thing to use. It is possible for automatic feeders and rollers to stretch a scanned image, albeit slightly. You can find it discussed on manufacturer support sites for Canon, HP, etc.

Nov 16, 21 9:45 am  · 
1  · 
x-jla

just import the image into cad, do a ref scale, plot to paper size, and print…

Nov 16, 21 9:49 am  · 
2  · 
pamp

This. Just draw a graphic scale on your sketch first.

Nov 16, 21 10:55 pm  · 
 · 
Non Sequitur

Just scan the drawing with a banana at the same time.  That way you can always know the scale.

Nov 16, 21 11:12 am  · 
5  · 
whistler

or a ruler, or am I just being too obvious!

Nov 16, 21 5:06 pm  · 
 · 
whistler

or better yet a banana with a hand drawn scale on it! Sharpies work great!

Nov 16, 21 5:07 pm  · 
2  · 

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