"Internet Corner" Articles
2D Bar Codes: A Picture is Worth 1000 (or more) Words
Society of Georgia Archivists Newsletter, Volume 41, Issue 2, Summer 2009 [PDF]
A bar code is an optical machine-readable representation of data. Linear bar codes are a familiar sight on products in retail stores, on packages, on passports, and on event tickets, to name a few examples. They save people time and energy, allowing more items (or people) to be more accurately processed in a shorter period of time. Originally, bar codes represented data in the widths (lines) and the spacings of parallel lines, and may be referred to as linear or 1D (one dimensional) bar codes. Stacked barcodes are linear barcodes are stacked on top of one another in the same space. A standard linear barcode can store approximately 20 digits. Additionally, they are only able to be read by a laser scanner horizontally and only on printed (non backlit) media.
As with most things computer-related, there is a trend for packing more information into the same (or smaller) area. Matrix (two dimensional) bar codes can offer higher data densities than stacked codes, and can be read vertically as well as horizontally. 2D bar codes are made up of a pattern of cells that can be square, hexagonal, or circular in shape. Data is encoded via the relative positions of these light and dark areas, and encoding schemes use error detection and correction techniques to improve reading reliability and enable reading of partially damaged symbols. They are scaleable and well-suited both as small ID marks on products and as conveyor-scannable symbols on shipped packages. All of these are created with specific software, although some have to be read with particular hardware, and others can be read by a mobile phone with camera capabilities. Interestingly, 2D codes can be read both on printed media and computer/tv screens.
Many archives use standard linear bar codes to uniquely identify boxes within the institution. The codes help deter misfilings and provide hard data on how “active” a collection really is. A linear bar code, however, only provides a link to the database where the metadata is stored. Imagine the possibilities of having content information directly on the box by encoding the information in a 2D barcode. It could help researchers quickly record the folder titles of a box as they are conducting their research, and be able to share that information with others who are working on the same topic. A scan of a document inside could have a 2D bar code imbedded in the scan to document where the original is located. There are many types of 2D bar codes, but discussed below are codes which have become ISO standards or are commonly used. Each section shows an example of the 2D bar code representing the SGA website address.
Aztec Codes
Aztec Code was invented by Andrew Longacre, Jr. of Welch Allyn Inc. in 1995 (later Hand Held Products Inc., now Honeywell Imaging and Mobility). The code was published by AIM International in 1997 and although the code is patented, it has been released to the public domain.
The symbol is built on a square grid with a bulls-eye pattern at its center for locating the code. Data is encoded in a series of circles around the bulls-eye pattern. Each additional circle completely surrounds the previous circle causing the symbol to grow in size as more data is encoded. A dark module is a binary 1 and a light module is a binary 0. The code is orientation independent. The smallest Aztec Code symbol is 15x15 modules square and encodes 13 numeric or 12 alphabetic characters. The largest Aztec Code is 151x151 and encodes 3832 numeric or 3067 alphabetic characters or 1914 bytes of data. No empty zone is required outside the bounds of the symbol. Aztec Code is supposed to be robust according to various printer technologies. It is also well suited for displays of cell phones and other mobile devices.
It is used for a variety of patient-safety applications, including patient identification wristbands and labels for unit-of-use medications, IV mixtures, blood products and specimens. It is also used by various companies for plane and train tickets sold online for customers to self-print, and has been selected by the airline industry (IATA's BCBP standard) for the electronic boarding passes. Several airlines send Aztec Codes to passengers' mobile phones for online (or paperless) ticketing purposes. The code can be displayed and scanned from the screen of any phone with a high enough screen resolution.
Data Matrix Codes
Data Matrix codes were invented by RVSI/Acuity CiMatrix, who were acquired by Siemens AG in October, 2005 and Microscan in September 2008. Data Matrix is covered today by an ISO standard (ISO/IEC 16022), and is in the public domain for many applications, which means it can be used free of any licensing or royalties.
A Data Matrix code is made up of black and white modules in either a square or rectangular pattern. Information on the code can be either text or raw data, and the data size can range from a few bytes up to two kilobytes. A Data Matrix symbol can store up to ASCII (8 Bit), 2335 alphanumerical or 3116 numeric characters.
It is used for encoding large amount of data characters and is ideal for marking very small containers. In addition, it is used by the pharmaceutical industry for unit dose and product marking. It was originally developed for the Space Shuttle Program, where millions of parts had to be tracked.
QR (Quick Response) Codes
A Japanese corporation named Denso-Wave created the QR code in 1994. The Denso-Wave Corporation has stipulated that the QR Code is clearly defined and made public. It is also freely usable by end-users. It became an approved ISO Standard (ISO/IEC 18004) in June of 2000.
A QR code can handle numerical and alphabetic characters, Kanji, Kana, Hirigana, symbols, binary, and control codes. Up to 7,089 characters can be encoded in one symbol. QR can handle the same amount of data in approximately 1/10 the space of a traditional bar code. It also has dirt and damage resistance capability. A maximum of 30% of codewords an be restored, depending on the amount of dirt or damage. The information can be read from any direction at high speeds. The Code system is used in combination with a QR Code printer (or QR Code creation software) and QR code scanner. The size of the QR code is decided by determining a symbol version, based on data capacity, character type and error correction level, and by setting a module size, based on the performance of the printer for printer or the scanner for reading.
Although initially used for tracking parts in vehicle manufacturing, QR Codes are now used in a much broader context, including both commercial tracking applications and convenience-oriented applications aimed at mobile phone users (known as mobile tagging). QR Codes storing addresses and URLs (Uniform Resource Locators) may appear in magazines, on signs, buses, business cards or just about any object about which users might need information. Users with a camera phone equipped with the correct reader software can scan the image of the QR Code causing the phone's browser to launch and redirect to the programmed URL. This act of linking from physical world objects is known as a hardlink or physical world hyperlinks. Users can also generate and print their own QR Code for others to scan and use by visiting one of several free QR Code generating sites.
MaxiCode
MaxiCode is a public domain, machine readable symbol system originally created and used by United Parcel Service beginning in 1992. MaxiCode has been standardized under ISO/IEC 16023.
A MaxiCode symbol (internally called "Bird's Eye", "Target" or "ups code") appears as a 1 inch square, with a bullseye in the middle, surrounded by a pattern of hexagonal dots. It can store about 93 characters of information, and up to 8 MaxiCode symbols can be chained together to convey more data. The centered symmetrical bullseye is useful in automatic symbol location regardless of orientation, and it allows MaxiCode symbols to be scanned even on a package traveling rapidly.
Semacodes
Semacode is a software company based in Waterloo, Ontario, Canada. It is also this company's trade name for machine-readable ISO/IEC 16022 data matrix symbols, a type of barcode resembling a crossword puzzle, which encode URLs. The Semacode website states that Semacode tags are an "open system" and that tag creation is "completely unrestricted," with the SDK software tools being free of charge for non-commercial use.
Semacodes are primarily aimed at being used with cellular phones which have built-in cameras, to quickly capture a Web site address for use in the phone's web browser. Potential uses for Semacode tags are still being explored, and will complement development of the concept of using mobile phones as devices for information gathering and exchange. Suggestions from the Semacode.org website include placing Semacode tags on nametags given to conference attendees. These tags could provide the corporate web address of each attendee's company, or their biography and contact details.
Shotcodes
ShotCode is a circular barcode created by High Energy Magic of Cambridge University. It uses a dartboard-like circle, with a bulls eye in the center and datacircles surrounding it. The technology reads databits from these datacircles by measuring the angle and distance from the bulls eye for each.
ShotCodes are designed to be read with a regular camera (including those found on mobile phones and webcams) without the need to purchase other specialised hardware. Because of the circular design, it is also possible for software to detect the angle from which the barcode is read. ShotCodes differ from matrix barcodes in that they do not store regular data--rather, they store a look up number consisting of 40 bits of data. This needs to link to a server that holds information regarding a mapped URL which the reading device can connect to in order to download said data.
For more information, visit:
Fun Trivia: The linear bar code celebrated its 35th birthday on June 26, 2009.
- The Bar Code Celebrates its 35th Birthday (Christian Science Monitor)
- Game Changer in Retailing, Bar Code Is 35 (New York Times)
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