How Much Speed Do You Need?

21 Sep, 2006 By: Henrik Vestermark

When it comes to wide-format scanning, today's high-end performance is more than enough for the typical AEC or GIS office.

At this year's ESRI user conference in San Diego, California, I spoke with many current and prospective customers in the AEC and GIS communities about the business benefits of wide-format scanning. It was clear that none of them was overwhelmingly concerned about scanning speed. In fact, most revealed that scanning speed was not an issue at all.

Initially, this surprised me a lot. For many years, scanner manufacturers have increased scanning speed, and every new generation of scanners has been faster than the one before. With the August release of eight new wide-format scanners from GTCO Calcomp, the company pushed the performance envelope to an amazing 12ips (inches per second) for black-and-white and 3ips for color scans for most of the models.

It has always been a good rule of thumb that if you increase scanning speed, you increase your productivity and thereby improve your bottom line. So, why was I hearing that scanning speed was not an issue? Did scanner manufacturers finally succeed in developing the technology beyond the needs of its customers?

To answer the question, we must look at some fundamental factors of scanning productivity in both black-and-white and color.

Black-and-white Scanning Capacity
Let's look at the GTCO Calcomp ScanPlus 6 LF542, a black-and-white scanner capable of scanning 6ips, and the ScanPlus 6 LF742, a 12ips black-and-white scanner. Below are the machines' productivity rates per hour based on a calculator developed by my company, The Other Solutions. This capacity scanning tool is available as a free download on our Web site.

The 6ips scanner can scan 48 E-size documents per hour at 400dpi, while the 12ips scanner is able to scan 53. Using these numbers to calculate the daily, monthly and yearly scan rates, we get the following results.

400dpi Scans
  ScanPlus 6 LF542/6ipsScanPlus 6 LF742/12ips
Hourly 48 53
Daily 384 424
Monthly 8,343 9,212
Yearly 100,114 110,542

The ScanPlus 6 LF542 can scan up to 48 E-size documents at 400dpi in one hour. The graph shows the range in the number of scans as dpi changes.

On the other hand, the ScanPlus 6 LF742 is able to scan 53 E-size documents at 400dpi in an hour.

Interestingly, there is only a 10% difference in the productivity of these two models even though the scanning speed is twice as fast in the ScanPlus 6 LF742. The second consideration here is that 100,000 drawings is a lot of drawings. Will you need to scan 100,000 documents in a year? Probably not. Most AEC, GIS and other CAD users who use in-house wide-format scanning tend to scan on demand, resulting in 100-2,000 scans per year. I found these scanning estimates:

  • A dedicated wide-format scanning service bureau averages approximately 200,000 scans per year.
  • A large city government converting paper documents to digital files typically has approximately 100,000 drawings to scan initially.
  • A medium city typically has 50,000 drawings to scan initially.
  • A small city typically has 10,000 drawings to scan.

Until now, in our calculations, we have assumed that most drawings scanned are good quality and can be scanned using default parameter settings. In reality, not all drawings are created equal. Some are medium to poor quality and require clean-up to result in the best possible digital documents. By considering these factors in our original equation, we get the following performance results.

400dpi Scans
  ScanPlus 6 LF542/6ipsScanPlus 6 LF742/12ips
Hourly 26 28
Daily 208 224
Monthly 4,519 4,867
Yearly 54,229 58,400

Now the difference between the performance results has dropped from 10% to 7%, but the overall yearly productivity is still 54,000-58,000 drawings.

Color Scanning Capacity
Now, what happens when scanning E-size color documents at excellent quality on the GTCO Calcomp LF742 (0.6ips and 1ips) and the ScanPlus 6 LF942 (1.5ips and 3ips)?

400dpi Scans
  ScanPlus 6 LF742/0.6ipsScanPlus 6 LF742/1ipsScanPlus 6 LF942/1.5ipsScanPlus 6 LF942/3ips
Hourly 16 23 29 31
Daily 128 184 232 248
Monthly 2,781 3,998 5,040 5,388
Yearly 33,371 47,971 60.486 64,657
Difference 100% 144% 181% 194%

Even in color, we can easily scan more than 33,000 drawings per year using the scanner with 0.6ips color speed at 200dpi. A five-fold increase in color speed to 3ips only doubles the throughput.

What the Numbers Tell Us
Although increasing 200dpi black-and-white scanning speed from 6ips to 12ips does increase early throughput, the doubled scanning speed yields only a 10% productivity gain overall.

In color scanning, a 1.5ips scan speed offers 81% better throughput over 0.6ips, but as you further increase scan speed to 3ips, the gain in throughput becomes marginal and nets a mere 7% increase in productivity overall. This disappointing result is due to the fact that the Firewire and USB interface and PC capacity begin to impede overall system performance.

When Good is Good Enough
Most scanners on the market today fulfill most black-and-white and color scanning needs. High-performance scanning speed seems appropriate for dedicated wide-format service bureaus where the sheer number of scans per year justifies purchasing one or more of these scanners. For the majority of design offices, however -- even most large firms -- the need for high-end speed simply isn't there.

Scanner manufacturers have pushed scanner speed to the point where capabilities exceed the requirements of the majority of customers. The truth is, entry-level scanners can fulfill many users' needs. But the fact that a wide-format scanner's throughput exceeds your needs doesn't mean you shouldn't invest in it. Most wide-format scanners today are at a price point that justifies purchase even if you scan as few as 500-1,000 drawings per year.

Editor's note: For more about calculating potential return on investment of a large-format scanner, see Henrik Vestermark's articles in the August 22 and August 23 editions of Cadalyst Daily.)

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