Over the last two decades vast amounts of spatial data have been converted from hard copy to digital media, leaving users with accuracy problems and a challenge: how to manipulate the scanned data to minimise the reduction in accuracy. Is the industry capable of solving these problems? Can it create solutions which will ensure its position in the future?
Steve Burke is image cell manager at the Geospatial Information Branch of the Defence Imagery and Geospatial Organisation. He says an informal survey of his colleagues revealed some of the shortfalls highlighted by high-level scan users.
Among them, inaccuracy, including an inability to maintain the map's geometry, is seen as the most serious. A loss of detail through scan lines and camera stitching, or through digitising at too low a resolution, is also a problem. Burke says GIB uses a minimum of 400 dots per inch, which leads to large file sizes. It is not uncommon for the branch to have files approaching or surpassing a Gbyte, which leads to further problems in file storage. He says scanners also suffer from insufficiently user-friendly interfaces.
Burke says GIB personnel can manipulate scanned data without any problem, and will go to at least a third-order transformation to overcome inherited accuracy problems by warping the scanned image, sometimes more than once, into position.
He also believes that developers and manufacturers are working closely enough with the industry to produce the necessary solutions to these conversion problems. But, he adds, high-level users still need standardised data exchange formats and higher optical resolutions on large format scanners, and all scanners should have a 16-bit option.
The National Mapping Division of Geoscience Australia is another prolific and demanding (in terms of quality) scanner user. In mid-2001 it purchased an Oce 4780 colour scanner to produce 'mid-range' scans with resolutions up 600 dpi.
An NMD spokesman describes its performance to date as 'meeting requirements' but says a range of shortfalls continue to exist in scanning technologies. Among them is the fact that affordable LCD, friction-fed camera scanners often do not achieve the accuracy required for GIS data acquisition. NMD geodata specifications require Helmert Transformation residuals of less than 50 metres for 1:250,000 scale mapping, which is not achieved with friction-fed LCD camera scanners. Data must then be vectorised with a less controlled transformation such as Affine or Projective. There is no doubt that large drum laser scanners produce better high-precision results.
Another problem with the current technology is that fine line work is not well preserved. Contours can disappear in steep areas on a 1:100,000 chart with 20 metre interval contours; this can greatly increase pre-vectorisation editing time.
Friction-fed scanners may also find it difficult to scan laminated surfaces and materials with thicker bases and hanging strips.
Technical support is still catching up with colour scanning technology.
For the future, NMD prefers the fast LCD friction-fed scanners, good software for de-skewing, cropping and colour substitution, and support of the popular output raster formats.
Rob Brown, channel manager of Sydney-based DES Pty Ltd, concurs that current scanner technology, including the glass, the CCD sensors, and camera stitching, presents challenges for high-level users.
'However, software interfaces are constantly improving,' he says, 'allowing users to scan and manipulate, including despeckling and scaling, to a much higher level than previously.'
DES is the sole distributor in Australasia of Colortrac large-format scanners, Best digital proofing software and Colorblind colour management software. Brown confirmed that sales trends are moving more towards colour scanners, as end users seek to increase the number of functions they can perform and to get a greater return on their investment.
Stephen Bennett, national IT manager of Southern Graphtec Systems, agrees. He said SGS, a distributor of large and small-format plotters and scanners, digitisers, vectorising software, document management systems and accessories, increased its sales of colour scanners last year by about 20%.
'Colour scanners now represent about 80% of sales compared to 20% for black and white units, and vectorising and colour separation software is overtaking digitiser sales,' he said.
'Raster-to-vector conversion software is getting better every year. Manufacturers are building symbol recognition into their packages. They can also train the software to separate the good information from the bad and even to recognise people's handwriting. But it is still only about 90% to 95% accurate even on a good drawing,' said Bennett.
SGS distributes the German OCR Graphikon software, which is updated at least once a year.
Another player in the marketplace is Sinclair Knight Merz, which last year bought out Abakos Imaging, a company dedicated to producing the Deskan Express Scanner. Nicole Kibsgaard, marketing and product sales manager of the spatial division at SKM, confirmed that global demand for large-format scanners had been increasing. Concurrently, the focus is shifting from document scanning to data conversion, boosted by the continual improvements in data conversion products.
David Lewis, managing director of Melbourne-based Autotech Computing, which provides large-format scanning solutions through sales and bureau services, says the accuracy of scanners is needlessly denigrated.
'Scanners provide the most accurate means of digitising information, and their accuracy can exceed 0.05%,' he says. In line with worldwide trends, his company has been selling scanners 'strongly' over the past two years - mainly to major GIS organisations - on the basis of their accuracy, quality output and high throughput rates.
Contrary to other sources, Lewis claims that the digitiser market is also continuing to grow, although it has shifted from pure digitising to estimating-type functions based on GIS information.
Richard Bates, managing director of Scan and Conversion Services in South Australia, has yet a different experience. He says that sales of stand-alone large-format scanners have fallen by 2% in the past year, in Australia and overseas. Sales of multi-type devices that offer both plan printing and black and white scanning are on the increase.
'People in organisations with 10,000 or more drawings love the idea of scanning, but they can oversimplify the process,' he said. 'It's really quite a complex operation that requires index and retrieval software, plus the expertise to use that software.'
Bates believes, however, that the market is becoming much more educated about the complexities of scanning and that the area offers huge opportunities for growth.
Sales of the company's own indexing and retrieval software, Data Collection and Data Reviewer, have grown by 40% a year worldwide for the last three years.
Noel Parkin, a sales engineer at Mandeno Electronic Equipment in Auckland, says that sales of small-format scanners are declining in the face of give-aways with PC sales. There is also a price squeeze caused by large players, such as Hewlett Packard, selling through department stores.
'However, large projects such as council archiving still require a colour scanner of at least a 0.05% accuracy level, and sales enquiries for high-performance digitisers that offer 0.005% and even 0.002% accuracy are increasing,' he said.
As for the continuing challenge of mismatched levels of accuracy in scanned data, he suggested rescanning some of the data or using the cleanup software that is standard with the better large scanners.
Interestingly, David Lewis of Autotech quotes international research that indicates that only about 10% to 15% of hardcopy spatial data worldwide has been converted to digital format. Add to that a recent Gartner prediction of 60% annual growth in document management over the next five years, and it looks as if scanners and their peripherals have a huge role to play in the foreseeable future.
Hazel Baker is a freelance journalist working in Sydney. She is a regular contributor to GIS User.
