scanning versus digitizing
Nicholas Napp
bru...@bashful.cc.utexas.edu "Bruce A. Boulanger" writes:
> Could someone please tell me what the difference is between scanning and
> digitizing? My email address is bru...@ccwf.cc.utexas.edu
Hi,
Scanning is a process whereby you run your drawings/microfiches/aperture cards/
whatever hardcopy original through a machine which is similar in design
to an overgrown fax machine. You feed the paper in at the top, and its passed
accros some kind of camera apparatus. This beast produces files in a range of
RASTER formats, such as TIF, PCX, or Group 4, which contain the image of your
original. This image can then be stored on your hard-disk, and retrieved
on demand. The huge stack of drawings you had has now been reduced to a few
CD-ROMS, or a hard-disk.
Sounds good? There is of course a snag ....
A CAD system stores all the lines/arcs/circles/thingummys as lines/arcs etc.
Doing a "list" in the program will tell you "line going from A to B, on
layer C, linetype D, colour E" etc. The line is a VECTOR entity.
Any part of the line knows it is part of a line, and all the above list of
properties. It is therefore "intelligent" (by line standards!).
However ...
the scanner works by breaking up the original drawing into tiny dots, or pixels.
The accuracy of the scan is dependent on the number of dots per inch (DPI)
the scanner is set to scan at. This means that what looks like an arc on your
drawing has been broken down into rows and rows of dots. When you take this
file to your CAD system, it doesn't see anything other than a bunch of dots,
so your nice drawing of arcs/lines/circles/doo-hickeys is useless.
Unless ... You purchase some additional software. You have 2 options, either
edit the scanned (or raster) image, or convert it to vector format.
Depending on what your goals are, either route may be preferable, or a mixture
of the two.
Digitzing basically means you buy a digitizer, strap your drawing to it,
and redraw it. A digitizer is a big (how big depends on your cash flow :))
flat thing, with a piece that looks similar to a PC mouse (a puck) attached
to it. The drawing is placed on the flat pad, and you manually redraw your
original drawing with your CAD package by clicking the puck and "tracing"
over the original drawing.
Both methods have their merits, but my money would be on scanning (obviously)
as its much MUCH faster, providing you have the right software !!!!
Hope that helps, any more questions, feel free to mail me
Nick
--
Nicholas Napp - Product Manager
The above opinions may not reflect the views of my employer
GTX Europe Ltd
Tel: (44) 0256 843555 (Fax: (44) 0256 24634 Email:g...@gtxeurop.demon.co.uk
GTX develop and supply world leading Raster to Vector conversion and editing
software across a range of platforms and operating systems.