Re: Scanner, write-ins, printer (was Re: Barcode -- printed ballot)

From: Alan Dechert <adechert_at_earthlink_dot_net>
Date: Sun Sep 21 2003 - 15:59:22 CDT

Ed wrote (quoting me):
>
> > We need to keep the string of characters containing the
> > encoded selections down to a minimum to ensure accuracy
>
> Accuracy is ensured by error-correcting coding, that is by adding
> redundancy in a controlled manner, not by removing all possible
> redundancy. Error correction must be part of the bar code
> standard we adopt.
>
In light of the testing I've done, I want to re-visit these comments.
Instead of "ensure accuracy," I should have said "ensure readability."
Accuracy does not appear to be a problem. When you swipe a barcode, the
thing either reads or it doesn't. I never saw a mistake in the output --
either while testing with Jan's barcode or reading codes on various
household products, books, shampoo bottles, beer cans, etc.

The one exception to this is that I found that it's possible for the scanner
to interpret some codes from non-barcodes. If you swipe it over some text
or other printed material [rarely] you can get some spurious output. I even
managed to read something from stripes on my shirt once (couldn't
replicate). This should not be an issue in our application since the
barcode will be the only printed thing on the ballot exposed to the scanner.
At this point, I have total confidence in Cue Cat accuracy.

Readability is an issue. It depends on the skill of the operator, the
length of the barcode, and the font size of the barcode. Barcode height is
also a factor but not a major one. As long as it's at least 1/4 inch in
height, it doesn't matter much. I think 3/8ths of an inch would be a good
height to work with. With a short barcode and large font, readability is
very easy -- not much skill required. For example, the code Jan gave for
ABCDE1234567890 at 22 points is very easy (it's about 1 1/4 inches). A
larger font will make it a little longer but makes it even easier to read (I
suppose there is a limit to how much larger the font can be while increasing
ease of reading -- we haven't tried fonts larger than 26 although I intend
to do so). The longest barcode Jan gave with 56 digits (about 3 1/4 inches)
is quite readable but requires a little more focus by the operator. I just
tried a usability test with my wife and found she was able to read the
longest barcodes -- with maybe an average of two tries -- after about 30
seconds of instruction and practice.

So, longer barcodes with a given font size can be read okay but batting
average is higher with shorter ones. It's no show-stopper if it takes a
couple of swipes to pick up the code; we're used to seeing grocery store
clerks making more than one attempt even with their industrial grade
scanners. But the demo will go more smoothly if we can successfully read
the code with minimal re-swiping.

I have found that it helps to move the scanner at a steady speed -- not too
fast and not too slow.

Alan D.
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Received on Tue Sep 30 23:17:07 2003

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