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   Attaching image files in AutoCAD drawings to a perfect scale will never happen with real precision because of inaccuracies in scanning.  But you can get close if you have an idea of the image file's scale factor.  And you should be able to do that even with a graphic scale.  Your chances of getting right on the first try are about 50/50.
Whenever I have to attach raster drawings I'll start with importing them at the proper scale factor.  I still check once it's in the drawing, and after that I'll perfect rotation.  Only then is it even remotely "safe" to trace or scale measurements.

That's just my 2 cents.
Dave.

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heinsite Members Profile Send Private Message Find Members Posts Add to Buddy List Senior Member Joined: 05.Feb.2009 Location: United States Using: AutoCAD 2014 Status: Offline Points: 640	Topic: Help rescaling Tiffs Posted: 04.May.2011 at 10:24
	Attaching image files in AutoCAD drawings to a perfect scale will never happen with real precision because of inaccuracies in scanning. But you can get close if you have an idea of the image file's scale factor. And you should be able to do that even with a graphic scale. Your chances of getting right on the first try are about 50/50. Whenever I have to attach raster drawings I'll start with importing them at the proper scale factor. I still check once it's in the drawing, and after that I'll perfect rotation. Only then is it even remotely "safe" to trace or scale measurements. That's just my 2 cents. Dave.
	Dave Hein, P.E. Hawaii District Engineer Kona International Airport AutoCAD Certified Professional Autodesk Expert Elite

Vladimir Michl Members Profile Send Private Message Find Members Posts Visit Members Homepage Add to Buddy List Moderator Group Arkance Systems CZ Joined: 26.Jul.2007 Location: Czech Republic Using: Autodesk software Status: Offline Points: 2117	Posted: 21.Apr.2011 at 11:47
	You can use the `SCALE` or `ALIGN` commands to rescale your image after `IMAGEATTACH`. Alternatively you can use a raster editor to prescale your image (and set its dpi) so that it will be scaled correctly when you attach it with a given scale factor (e.g. 1 or 100).
	Vladimir Michl (moderator) ARKANCE - https://arkance.world - Autodesk Platinum Partner

TadKa Members Profile Send Private Message Find Members Posts Add to Buddy List Newbie Joined: 21.Apr.2011 Location: Australia Using: None Status: Offline Points: 1	Posted: 21.Apr.2011 at 02:29
	Hi there. I apologise if this is in the wrong place/forum but hopefully someone can help me because I can't seem to find anything out there. I have scanned some drawings (from microfilm apperture cards) of various sizes at 300dpi but on the drawings are a ruler/scale. Now somehow I want to use that ruler to scale each drawing so that the entire collection will open up to correct scale and users can print them and use them more accurately. Any help with this will be greatly appreciated. Thanks Edited by TadKa - 21.Apr.2011 at 02:30

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