Topic: Scanning drawings

[Anonymous]

How accurate is a paper drawing that has been scanned and converted into a cad file?  I've seen advertisers say they can produce 100% perfect cad files.  If this is true, it certainly is amazing.

[MP]

How accurate is a paper drawing that has been scanned and converted into a cad file?  I've seen advertisers say they can produce 100% perfect cad files.  If this is true, it certainly is amazing.

Operative word: advertisers. I've never seen anything better than about 75% success ratio given a general mix of graphical and textural info. Admittedly it's been years since I looked into said kind of software but label me very skeptical, claiming 100% is salemanship at its finest.

[pmvliet]

Are they really scanning and vectorizing or are the actually re-drawing all the elements. If the are really re-drawing it very well could be 100% of what they were given. If something was labeled 50' but was really drawn at 40', they will do the same.

Keep in mind most of that work is shipped out to SE Asia/India

I too haven't looked into that work for about 5 years so maybe things are different.

[Keith™]

I too echo that sentiment....most plotted drawings are already not to scale and may be skewed or unevenly scaled due to plotting errors, copy correction or other unforseen scaling problems. I would expect the most accurate drawings are probably simply redrawn using cheap labor....

[Serge J. Gianolla]

To add to Keith's comments, there will always be distortion of the media, even for the simple fact that humidity is present in the air... will be absorbed by blueprints. We have also seen scanners that were stretching the media along the major axis when feeding! More expensive exercise, but if accuracy is crucial, better redraw. The only time we have seen scanning as worthwhile is for large companies wanting to keep 1000's and 1000's dwgs drawn manually in past 100 years, and want to keep 'm as historical records - not to be used/modified... It is easier to fit them on few CDs than having to rent many rooms for plan storage [or at least to reclaim that wasted space].

[Jassper]

To add to Keith's comments, there will always be distortion of the media, even for the simple fact that humidity is present in the air... will be absorbed by blueprints. We have also seen scanners that were stretching the media along the major axis when feeding! More expensive exercise, but if accuracy is crucial, better redraw. The only time we have seen scanning as worthwhile is for large companies wanting to keep 1000's and 1000's dwgs drawn manually in past 100 years, and want to keep 'm as historical records - not to be used/modified... It is easier to fit them on few CDs than having to rent many rooms for plan storage [or at least to reclaim that wasted space].

Thats what we are doing here; We have a new Oce TDS400.
All the "Old" (back to 1880) are being scanned in to have a record copy of them and then the originals are shipped out to the Main Archive. We also take the final stamped plots - scan them in - and create bid sets from the PDF file thats created. Makes it sooo much easier.

Little :O)