Petrie Museum object tagging project by sdfsb346f

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									Object tagging
                    at the
Petrie Museum
An investigation into the potential use of machine-readable
object identification tags in the extensive and diverse
collection of the Petrie Museum of Egyptian Archaeology,
University College London.

                       Ivor Pridden
                        July 2003
Table of contents

1. Introduction ........................................................................................................................ 3
2. Tagging system parameters ................................................................................................ 4
2.1     Tag attributes .................................................................................................................. 4
  2.1.1     Materials .................................................................................................................4
  2.1.2     Dimensions and visual intrusiveness......................................................................4
  2.1.3     Ease of encoding.....................................................................................................4
  2.1.4     Data retention .........................................................................................................4
  2.1.5     Cost.........................................................................................................................4
  2.1.6     Compatibility ..........................................................................................................5
2.2     Reader and display system ............................................................................................. 5
  2.2.1     Scanning safety.......................................................................................................5
  2.2.2     Scanning range .......................................................................................................5
  2.2.3     Tag targetting..........................................................................................................5
  2.2.4     Portability ...............................................................................................................5
  2.2.5     Ease of use ..............................................................................................................5
  2.2.6     Data security ...........................................................................................................5
  2.2.7     System cost .............................................................................................................5
  2.2.8     Implementation time...............................................................................................5
3. Options for a working system............................................................................................. 6
3.1     Tag attachment, packing and mounting options............................................................. 6
  3.1.1     Direct attachment....................................................................................................6
  3.1.2     Containers...............................................................................................................6
  3.1.3     Foam support ..........................................................................................................7
  3.1.4     Tied-on tags ............................................................................................................7
  3.1.5     Object mounts.........................................................................................................7
3.2     Tagging technology and encoding options..................................................................... 7
  3.2.1     Tag types ................................................................................................................7
  3.2.2     Tag readers .............................................................................................................9
  3.2.3     Computing and data communications ..................................................................10
3.3     Functionality options .................................................................................................... 11
  3.3.1     Tag data ................................................................................................................11
  3.3.2     Software................................................................................................................12
4. Use of machine-readable tags in other collections ........................................................... 12
5. Trial at the Petrie Museum ............................................................................................... 13
5.1     Barcode generation....................................................................................................... 13
5.2     PDA scanner................................................................................................................. 14
5.3     Wireless network .......................................................................................................... 15
5.4     PDA software ............................................................................................................... 15
5.5     Laptop computer and hand held scanner ...................................................................... 15
5.6     Scanning tests ............................................................................................................... 16
6. Recommendations and suggestions.................................................................................. 17
7. Conclusion........................................................................................................................ 18
References ................................................................................................................................ 18
Appendix 1: Equipment and software used for the trial........................................................... 19
Appendix 2: Barcode scanning distance table.......................................................................... 20




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1. Introduction
The Petrie Museum of Egyptian Archaeology at University College London (UCL) holds
approximately 80000 objects from Egypt and Sudan covering a wide time span from the
Palaeolithic through to the Islamic period, and has a number of strategic aims to make this
varied collection more accessible to a range of target audiences. The current prime objective,
supported by the Heritage Lottery Fund, is to relocate the museum to a site where greatly
improved access and collection care can be provided. A digitisation project funded by the
Designation Challenge Fund (DCF) resulted in the transfer of object details into an Adlib
collection management database and the launch in April 2002 of an illustrated searchable
catalogue of the collection on the World Wide Web (http://www.petrie.ucl.ac.uk); these
resources are now being exploited by further projects working towards the Petrie Museum’s
strategic goals. The DCF-funded tagging trial covered by this report is one such project,
contributing towards the intended establishment of an “integrated museum” where the
museum’s real and virtual resources would converge, and the findings will also have direct
application during the process of relocating the collection.

This project was carried out to investigate the practicality of using machine-readable object
tags such as barcodes to link to the data in the digital catalogue. Successful implementation of
such tags would meet several objectives:

   •   To automate number recording during common collection management tasks such as
       checking object locations, temporary removal for conservation or loan, and condition
       surveys.

   •   To automate tracking of objects during museum relocation. It will be necessary to
       keep track of the location of every object during packing, transport and placing in the
       new building, and experience of recording object numbers during the digitisation
       project demonstrated that using a manual system would be time-consuming and error
       prone.

   •   To simplify and standardise recording of research use of the collection. The Petrie
       collection is an important teaching and research resource, and getting out objects for
       study is a frequent task for the museum staff. The process is currently recorded on
       hand-written forms, but if researchers were issued with personal tags then a system
       similar to a library issuing system could be used to simplify the administration and
       enable more detailed analysis.

   •   To provide the base technology to enable enhanced interpretation of objects for
       visitors. Limitations of traditional labels include the space available for them and the
       amount of time visitors are prepared to spend reading the text. A more flexible
       alternative would be to lend visitors a portable device that could read a tag adjacent to
       an object and retrieve information from the catalogue. This service could potentially
       be enhanced in many ways by expanding the stored data, for example to offer a choice
       of languages, different levels of detail and audio commentary.

The report defines a number of requirements that should be met by the components of any
tagging system to be used in the museum, and considers various options available to meet
these requirements. Trials carried out with barcode tags in the Petrie Museum are described,
and recommendations made for further implementation.




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2. Tagging system parameters
Tagging systems comprise tags or labels that store information in some machine-readable
form, devices to write data onto the tags and readers or scanners to retrieve that data. This
section lists the important parameters that a new tagging system in the Petrie Museum should
be expected to conform to, with the safety of the objects being a primary concern. Many of
these parameters would apply more generally to other collections. Requirements for the tags
themselves are listed first, followed by the hardware and software to read them.

2.1 Tag attributes

2.1.1 Materials
The tags will be in close proximity to the objects, possibly in closed containers, and may
come into direct contact with them. It is essential that they consist of, or are encapsulated in,
archival/conservation grade materials that will cause no adverse effect on the collection.
Sample tags should be tested in the conservation laboratory if there is any doubt about their
composition.

2.1.2 Dimensions and visual intrusiveness
In a collection with many small objects close together, the appearance of the tags could be
very intrusive. This effect must be minimised, although it will be difficult to eliminate where
space is limited.

Tag sizes will be limited by the space available and the capabilities of the technology. Objects
in the collection range in size from a few millimetres to over two metres. Many of the
smallest are currently stored in open cardboard boxes approximately 3cm square, but these
boxes are not thought to be acid-free and will be discarded during museum relocation if not
before. Storage is gradually being migrated to foam cut-outs or inert polystyrene “crystal”
boxes, the smallest crystal boxes measuring about 3.3 x 5.3cm. Tags must be available for the
selected system that will fit in the smallest boxes. Tags may also be placed inside display
cases, where they should be no larger than necessary for reliable scanning through the glass.

2.1.3 Ease of encoding
It should be easy for museum staff to encode a new tag whenever required, for example to
replace one that has been damaged and become unreadable, even if the original tags are
purchased in bulk ready coded.

2.1.4 Data retention
Tags should have long-term data retention, as renewing them all would be a major task. It is
not possible to predict how long any particular reader technology will be available, but certain
that it will become obsolete at some time and compatible reader devices will eventually be
unobtainable. The provision of a human-readable identifier on each tag would be highly
desirable for reference when automatic reading failed, and convenient at other times.

2.1.5 Cost
A budget has not been set for full implementation in the Petrie Museum, but the cost per tag
needs to be low given the quantity that would be required for the whole collection. Other
collections will clearly have their own financial constraints and may be able to justify more
complex tags with higher unit cost if there are fewer individual objects.




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2.1.6 Compatibility
The tags should use a standard coding system so that the museum is not dependent on
equipment from a single supplier. This would also allow for potential interoperability with
systems in other collections.


2.2 Reader and display system

2.2.1 Scanning safety
Scanning a tag must not involve any form of energy at a level high enough to be harmful to
humans or objects, for example only the lowest power lasers would be acceptable.

2.2.2 Scanning range
The scanning range must be at least 10 cm, sufficient to minimise the risk of accidental
physical contact between the reader device and objects close to the tag being scanned. It
should be possible to scan tags positioned several centimetres or more behind the glass of
display cases.

2.2.3 Tag targetting
Where small objects are stored together there will be many tags only 2 or 3 cm apart. It must
be possible for the system to discriminate between these to obtain the data from the target tag,
either by using a narrow scanning beam or by displaying a list of adjacent tags and allowing
the user to select the one required.

2.2.4 Portability
The reader and display may be integrated in one device or separate units, but must be easily
portable around the museum while also being sufficiently robust. A trolley-mounted system
would be acceptable for staff use, but visitors will want a lightweight device that enhances
their visit rather than being a burden.

2.2.5 Ease of use
The reader must be easy to operate using one hand or even hands-free, and give a clear
indication of a successful scan. The software interface, especially any version available to
visitors, should be simple and easy to use.

2.2.6 Data security
The system must provide different levels of data access depending on the user. For example
facilities to create and update object location data on the central database from the tag reader
must only be accessible to authorised staff.

2.2.7 System cost
Multiple sets of equipment will be needed for issuing to visitors, therefore purchase and
running costs must be affordable. It would be desirable to use established off-the-shelf
technology, if it can provide the required functionality, so that additional units can easily be
obtained to meet demand rather than risk initial over-stocking.

2.2.8 Implementation time
The process of tagging the whole collection will be a major exercise for the museum. The
time taken to associate a tag with an object must be minimal; for the Petrie collection each
extra second per object will add over 22 hours to the total work time.




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3. Options for a working system
This section describes the options considered when selecting a system to trial in the Petrie
Museum that would most closely conform to the parameters defined above. The means of
keeping an object and its tag together are discussed first, followed by the different tagging
technologies and finally the functionality that could be provided by the system.

3.1 Tag attachment, packing and mounting options

The objects in the Petrie Museum collection are very varied in size, shape and material. One
of the main problems this project set out to investigate, and one with no single solution, was
how to keep an object and its tag together without compromising the safety of the object.
Some of the same considerations apply as when marking with a human-readable number
(MDA Fact Sheet: Labelling and Marking Museum Objects), but technology limitations
further restrict the size and shape of machine-readable tags which satisfy all the requirements
(see section 3.2). A number of practical methods of tag positioning are possible, and the most
appropriate will depend on the type of object, its condition and location. Aesthetic
considerations and scanner range will influence the positioning of tags in display cases if they
are to be scanned from outside the case.

3.1.1 Direct attachment
Most of the Petrie objects have their accession number (the “UC number”) written somewhere
on the surface in permanent ink, usually between protective layers of Paraloid B72 acrylic
resin as recommended by MDA (Paraloid B72 is a colourless acrylic resin much used in
conservation for its stability and reversibility). Some museums write or print the accession
number on archival paper which is then stuck to the object, and it would be possible to safely
affix certain types of tag directly to objects having a suitable surface using Paraloid B72 as an
adhesive, but the method was ruled out for this collection for several reasons. The biggest
disadvantage is that the tags would be larger than many objects, for example small scarabs
and amulets, or at least obscure significant areas. Also for line-of-sight scanners the object
would often have to be manipulated to reveal the tag, only paper-thin tags could be used but
dirt or abrasion could render printed tags unreadable, the effect on display would be
unattractive, and attaching the tags could be very time-consuming.




                    Figure 1. Cardboard and plastic boxes for small objects

3.1.2 Containers
Many objects need to be repacked in conservation grade containers with one object and tag
per container, and ideally it should be possible to scan a tag without moving the object, so for
tags such as bar-codes additional space may be needed to position the tag where it is visible to
the scanner beam. Objects smaller than the practical tag size, such as small scarabs, will need
larger containers than the 3cm square lidless boxes many of them are currently in, and should
be packed so that the tag does not conceal the object (Figure 1). To protect printed tags from
dirt and scuffing they would be best placed on the inside of crystal boxes facing outwards and
held in place by the object packing, or covered by clear protective film if on the outside of a
container.

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Most of the existing storage drawers are very crowded, and if all objects were to be re-packed
in individual containers they would occupy significantly more space, although the use of
lidded boxes instead of the current open ones would enable more stacking than at present.
However individually stacked containers would be quite inconvenient when searching for an
object, and it would be desirable to install a system of lift-out trays in some of the drawers so
that a layer of objects could be removed to allow scanning of tags in the next layer. As there is
no free floor space in the museum to install additional storage units, it will not be possible in
the current premises to arrange the tags for optimum scanning without handling objects, but
this could be taken into account when designing storage for a new building.

3.1.3 Foam support
Where objects are stored in drawers in cut-out foam without containers it may be sufficient to
cut a slit in the foam next to each object to hold its tag in a readable position. Barcodes in
visible storage drawers would need to be angled so that they can be scanned from above.

3.1.4 Tied-on tags
A small proportion of the objects such as re-strung beads already have identification labels
tied on to them. Tags with a perforation to take a thread or tape could be affixed in the same
way and also tied to other objects with a sufficiently strong attachment point and stable
surface that will not be abraded by the tie.

3.1.5 Object mounts
If an object has been fitted with a display mount, it may be appropriate to attach its tag to the
mount. Alternatively the tag for a displayed object could simply stand next to it on the shelf.


3.2 Tagging technology and encoding options

3.2.1 Tag types
Two fundamentally different families of machine-readable tags were investigated for this
project, printed symbols and radio frequency identification (RFID) tags. Both of these are
widely used in commercial applications, RFID less so as it is younger technology and has not
yet attained the same level of standardisation.

Printed symbols include the familiar barcodes found today on almost all packaged goods,
together with more complex barcode-related symbols and the machine-readable alphanumeric
characters found on cheques. Most barcodes in common use are coded in a one-dimensional
or linear symbology, where the code consists of a series of bars and spaces with a small
number of fixed width ratios. Height of the bars is less significant, although it is specified in
standards for particular applications – higher bars simply add redundancy and thus give more
chance of a good read when the scan beam crosses the code. Reading performance is
dependent on the contrast between bars and spaces under the red scanning light, the optimum
being black bars printed on white but some colour combinations will work e.g. blue bars and
red spaces. There are many different 1-D barcode symbologies, using between 2 and 5 bars
and spaces to encode each character; some were designed for efficient encoding of digits
only, while others can handle longer character sets. Other features can include fixed or
variable length, special start and stop characters and check digits to help guard against
decoding errors. The Code 128 symbology, so named because it can encode the 128 ASCII
characters, is particularly flexible as it has three variations, character sets A, B and C, with the
capability of switching sets within a barcode. Code 128 set A includes upper case letters,
numbers, punctuation and special function characters such as tab, set B has lower case letters


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instead of most of the special characters, and set C provides very high density number-only
encoding.

Product barcodes are examples of standard structured codes, in this case fixed length numbers
including both manufacturer and product codes, and are coordinated by EAN International
(http://www.ean-int.org) in Europe and Uniform Code Council Inc. in the US. These
organisations issue numbers to ensure that every product has a globally unique code number,
and define special symbologies such as EAN13 to be used for marking goods so that they can
be read by any retail point of sale equipment. As its name suggests, an EAN13 code always
consists of 13 digits, beginning with a manufacturer code of 7 to 9 digits allocated by EAN
International, followed by a product number allocated by the manufacturer and finally a check
digit calculated from the digits to help detect read errors. Similar structures based on the
International Standard Book Number (ISBN) are defined for barcodes on publications, and
several national post offices have developed their own codes for mail handling. Note that
structured codes are distinct from symbologies, although some codes have special
symbologies defined. A standard structure has not yet been established for barcodes to be
used on museum objects. Figure 2 shows the relative sizes of a 12-digit number printed in the
Code 39, EAN13 and Code 128c symbologies.




                   Figure 2. Relative sizes of three common symbologies

A less common type of printed tag uses a two-dimensional “barcode” that can store much
more data than a 1-D type in the same space. There are more than 20 different 2-D
symbologies, some recognisable as derived from stacked 1-D codes while others are more an
array of dots than bars, and some can store 2000 or more characters. Descriptions of a number
of 2-D symbologies and links to further information can be found on the web (e.g. Adams
Communications). A recent development in product marking is the specification by EAN and
UCC of a family of reduced space symbologies which can encode product numbers in a
smaller space with the option of adding a 2-D component. The extra data capacity was not of
interest for this project as object information will be retrieved from the existing central
catalogue database, therefore 2-D barcodes were not investigated further.

RFID tags are transponders containing memory circuitry and an antenna and are available in
both active and passive forms. The integrated circuit gives RFID tags a level of intelligence
and thus more capability than barcodes but currently at much higher cost. Active tags contain
a built in battery and have a much greater range, but they cost several pounds each and must
be replaced when the battery runs down, so are of no interest for tagging a large number of
stored museum objects.

Passive RFID tags have no battery and are activated by taking power from the radio signal
transmitted by a reader device, consequently they can only return a weak signal which may be


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affected by the proximity of large metal objects. In their simplest form they are familiar as
security tags in shops, but could only enhance museum security if difficult to remove from
objects. Current RFID systems are mostly proprietary to their manufacturers with little
attempt at standardisation for interoperability, but this situation will improve as commercial
use increases. The tags vary in physical form, memory capacity and radio frequency, and
expert advice would be needed to select the best system for a particular application. A useful
basic primer on RFID is available on the website of Automatic Identification Manufacturers
(AIM), a trade association, at www.aimglobal.org. At least one system has been developed for
use in museums, the Talking-Tag system from Helicon Conservation Support b.v. in the
Netherlands (www.helicon-cs.com) based on I.Code tags made by Philips.

Data retention should not be a problem for barcodes printed on acid-free card with carbon-
based ink or toner, provided that the printed surface is protected from abrasion and excessive
dirt. RFID tags may have shorter data retention capability than barcodes, e.g. Philips state a
minimum of 10 years retention for the memory chips of their I.Code tags.

Bar codes can be printed at a size to suit the application, within certain practical limits, while
RFID tags are manufactured in a variety of sizes and shapes including thin label types. KTP, a
UK supplier of tagging systems, quoted a minimum of approximately 30 pence per passive
RFID tag (£24000 to tag 80000 objects). Researchers at the AutoID Centre
(www.autoidcenter.org), a multinational organisation sponsored by a number of major
manufacturers and retailers to research smart labelling systems, have stated that the cost of
RFID needs to fall to 3p per tag for mass use, but it is not clear when that will be achieved.
Barcode tags could be printed in-house for less than 0.5p each, and it is difficult to see how
RFID today offers a sufficient advantage to the Petrie Museum to justify its much greater
cost.

3.2.2 Tag readers
Barcode readers work by shining light of a particular wavelength, usually somewhere between
630 to 680 nm in the red range, onto the printed code and reading the intensity of the reflected
light to detect bars and spaces. They can be connected to a personal computer or specialised
equipment such as a shop till, and generally have decoding capabilities built in to recognise
the symbology of the code being read and translate it into a string of characters, removing
special start and stop characters and carrying out check digit validation if present. The
decoded barcode usually appears to the user as if the data had been entered via the computer
keyboard.

The simplest form of reader is the pen or wand type which has to be moved by hand along the
code; these would not be suitable in the museum as they usually need to be in direct contact
with the barcode which would endanger adjacent objects, and with repeated use they wear
away the printed bars.

The familiar hand held pistol-grip type readers found in many shops and libraries are
classified as either laser or charged couple device (CCD) types according to the technology
used to detect the code pattern.

CCD readers use light emitting diodes (LEDs) to illuminate the barcode and an array of 2000
or more CCDs to detect the pattern of bars and spaces. This system has the advantages of low
cost, high scan rate, no potential laser hazard and no moving parts, but the major disadvantage
for many applications of having to be held within a centimetre or so of the code. CCD readers
with similar range and cost to laser readers have come on the market recently, and having lost
the short range disadvantage they may in future take over much of the laser market.


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Laser readers use a low power laser beam and moving mirror to scan the code and a
photodiode to measure the amount of reflected light of the laser’s wavelength. The lasers used
in hand held barcode readers usually have a maximum output power of less than 1 milliwatt,
classified as Class 2 in the UK, although long range models use more powerful beams of 1-
5mW and are rated Class 3a. A Class 2 laser is not harmful to the skin, and in a barcode
reader the laser power is dispersed further by the scanning action; the only risk is to the eyes
and a person must not stare directly into the beam, although the blink reflex would normally
give adequate protection and momentary exposure and reflections from glass surfaces are not
known to be harmful. No published evidence could be found that exposure to the scanning
beam would damage museum objects, but 3-D laser scanners are increasingly being used to
record objects for replication apparently without harm. Simple laboratory tests carried out by
a conservator with a 1-5mW laser pointer on a variety of organic materials showed no visible
change after prolonged exposure (Bergeron 1999).

The simplest hand-held scanners scan along a single line at about 40 scans per second and can
decode the common 1-D barcode symbologies. Reading range varies from model to model
and is also dependent on the size and print quality of the barcode, but up to about 15-20cm
would be typical with the size of code likely to be used in the museum (see Appendix 2). The
reader must be oriented so that the scan line crosses all the bars, although the barcode can be
scanned either way up, and many readers sound an audible beep after a successful read.
Omnidirectional readers as used at supermarket checkouts can read a barcode at any
orientation by firing the beam in multiple directions, but there are very few hand held models
available and they are more expensive and bulky than the single scan line readers.

Laser reader attachments are available for general purpose personal digital assistants (PDAs)
such as the Compaq Ipaq range, and there are one-piece portable units with a built-in scanner
and small display for use where a more robust device is required. Symbol Technologies Inc.
produce a range of “hands free” wearable systems consisting of a miniature laser scanner
worn on the index finger with a thumb-operated trigger and connected to a small computer
strapped to the forearm; these are considerably more expensive than hand held devices and it
is doubtful whether it would be possible to handle museum objects safely while wearing such
a system.

Reading 2-D codes is more complex than 1-D and requires more expensive equipment. Some
symbologies can be read with modified versions of the CCD and laser readers used for 1-D
barcodes, while others are decoded using software to process an image of the symbol captured
with a video camera.

RFID readers, also referred to as interrogators, may be fixed or portable devices. They vary in
complexity and functionality depending on the tags which are to be read, but all include an
antenna to transmit and receive radio signals to transfer the data stored in the tag. Techniques
have been developed to handle situations where multiple tags are within range of the reader,
for example a tag can be told to stop transmitting when its data has been received. If tags are
to be encoded or updated in-house then a programmer device will be required, and this
function is combined with a reader in some units.

3.2.3 Computing and data communications
Once a tag has been read successfully, the decoded data is ready to be used by a computer
connected to the reader or passed on to a central system. For museum collection management
a laptop or desktop PC running some version of Microsoft Windows is the most likely, but
almost any system could be used as long as the reader can be connected in such a way that the


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decoded characters appear as if typed on the keyboard. This may be achieved either through
software or by means of a connector called a keyboard wedge if the computer has a separate
keyboard. Portability is important if the system is to be used where objects are stored, in this
case a laptop computer on a trolley would be a good compromise between convenience and
screen size for staff use.

Selection of tag-reading devices for use by visitors involves considerations which may be less
relevant for staff equipment, including weight, size, security and simplicity of use.
Audioguides have evolved over several decades and are now available and apparently popular
in many museums and galleries, but digital multimedia information systems are still at an
early stage, although much experimental work has been done (Schwarzer 2001). PDAs such
as Compaq / Hewlett Packard Ipaqs are being used for many projects because they can handle
audio recordings and display images and video, run web browsers and custom-written
software and have various connectivity options. This flexibility makes a PDA a suitable
choice for the Petrie Museum to trial and prices are decreasing, although the unit cost
including a barcode reader is still approaching £1000. There is some convergence between the
functionality of PDAs, digital cameras and mobile phones, and it is possible that in the future
visitors will be able to use their own devices to retrieve information from the museum server.

A means of accessing data on central servers from anywhere in the museum will be required.
Cable connection to multiple data ports or docking stations is not practicable given the floor
layout, and collecting data for periodic batch transfer would not provide the desired
functionality. Many PDAs and laptop computers have built-in infra red connectivity, but this
has a short range of only 1-2 metres. Bluetooth wireless connectivity is becoming more
common but this only covers a range of about 10 metres. At present, the most viable solution
for the museum using established technology is “wi-fi” wireless networking to the IEEE
802.11b standard, giving a range up to about 30 metres indoors depending on the location of
walls and other obstructions and with a maximum data transfer rate of 11 Mbits per second.
Equipment is becoming available conforming to the new 802.11g standard, which operates
over a similar range but can transfer data several times faster and is claimed to be backwards-
compatible with 802.11b so that older equipment will continue to operate (at its original
speed).


3.3 Functionality options

3.3.1 Tag data
If tagging is to be implemented for a collection then decisions have to be made about what
should be tagged and what data should be on the tag; the larger the collection the more critical
it is to define a workable system before starting.

The minimum sensible granularity would be to use one tag for each accession number. In the
Petrie Museum there are inconsistencies in the object numbering due to the number of people
involved in registering the collection over many years. Many UC numbers are subdivided by
appending alphabetic or Roman numeral suffixes to mark items which may be either parts that
were originally joined in one artefact, or sets of similar objects, or dissimilar objects that were
found together on excavation. Allocating a separate tag to each suffix would probably not be
useful while the objects are stored together, but extra tags should be allocated if and when the
items are separated. A further complication is that a single number, with or without a suffix,
may cover multiple physical items which may be in split locations e.g. part on display and the
rest in store. It would not be practicable to tag every separate item since there are grouped



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items such as boxes containing many thousands of beads, but a separate tag could be used for
each box or each set of pieces in a different location.

In a small collection or where the objects were arranged in an ordered number sequence it
would be possible to include the accession number in the tag data, but this would not be
practicable in the Petrie Museum. The tag data will be linked to other object information on
the database, so the main requirement is for each tag to be unique. The MDA was approached
but had no guidance for the format of object tags. A simple set of sequential numbers would
be adequate, however in an attempt to make the codes recognisable outside the museum an
option would be to define a structure prefixing the unique number with the four digit
Resource registration number (0117 for the Petrie Museum).

As well as tagging the objects, each object location such as a storage drawer or display shelf
should be given a tag containing a location code to allow for object location checking and
move recording. Location codes can simply be unique numbers, with a database table linking
the numbers to location details.

3.3.2 Software
Software is required to interface with the tag reader to record the location data for each tagged
object, and subsequently to update the location each time the object is moved. The assignment
of location-type codes to members of staff and researchers would allow the same software to
record temporary removal of an object from storage. One possibility would be to interface to
the UCL library system using the barcodes issued to library users, alternatively researchers
could be allocated temporary codes for the duration of their visit. Journaling of object moves,
including the reason for each move, would enable later detailed analysis of handling of the
collection. Software to print or program tags would also be needed unless they are to be
purchased encoded and ready to install.

Software for the visitor information function needs to run on a lightweight portable device
and should be simple and intuitive to use. Reading an object tag can retrieve catalogue data as
on the current museum website, but the same tag is potentially the gateway to future
additional information limited only by the resources available to create it. A bookmarking
feature could allow a visitor to note items for later study; in some electronic guidebook trials a
facility has been provided for visitors to forward information to their personal email address.

The Petrie Museum central object catalogue uses the Adlib database system with staff access
provided by PCs running Microsoft Windows 2000 or Windows XP. The database can be
extended to incorporate tag data, but unfortunately the version of Adlib currently in use will
not run on PDAs and does not provide a supported means of access from other software. A
version of Adlib has been announced to run on PDAs running Windows CE, such as the Ipaq,
but will operate in batch mode on a subset of records downloaded from the main database and
had not been delivered at the time of writing. Therefore with the present system it would be
necessary to have a separate mechanism for PDA access for visitors, and this could be based
on the extracted data held in a MySQL database which is already used by the museum
website. The most flexible means of delivering information to visitors would seem to be
through a web browser interface, since browsers are available to run on almost any computer.
Careful design is required to work within the limitations of the small PDA screen size, and
additional functionality could be developed as resources permit.

4. Use of machine-readable tags in other collections
There has been some use reported of machine-readable tags, mostly barcodes, for collection
management and no doubt they are also used elsewhere but still only in a small minority of


                                               12
institutions. None of the known implementations stated an intent to provide visitors with
information by reading the tags. The initial implementation of a tagging system has often
been prompted by a relocation of the objects, probably because the time and cost are difficult
to justify at any other time, although there are ongoing benefits. The English Heritage Ancient
Monuments Laboratory developed a barcoding system in 1991 to record the move of their
bulk finds store, using Code 39 symbology to encode accession numbers and shelf locations
(Jewess 1995). The Musée des arts et metiers in Paris also used Code 39 to track objects
during and after the move to a new reserve store (Picard 1998). Six institutions, all in the US,
responded to a web-based survey of barcoding for museums in September 2002 (Power
2002). An inventory system using barcodes and with a web browser interface has been
developed by Museum Victoria in Melbourne specifically to supplement the KE EMu
collection management system, and from April 2003 it was made freely available to other
users of that system (Hawkins 2002).

Only one large scale museum application of RFID tags could be found: In 2001 the Boijmans
Van Beuningen museum in Rotterdam started using the Helicon Talking Tag system on its
collection of 15000 drawings, citing both object tracking and security benefits
(www.semiconductors.philips.com/markets/identification/products/icode/).

An increasing number of portable visitor information systems are being experimented with,
most commonly using infra-red beacons either next to selected objects or positioned at
intervals to detect the visitor’s location in a gallery, e.g. the Hypertag Magus Guide trialled at
the Fitzwilliam Museum in 2002 (www.hypertag.com). The Electronic Guidebook project at
the Exploratorium in San Francisco has included barcodes and RFID tags but not for every
object (www.exploratorium.edu/guidebook/). Where a relatively small number of tags are
installed the unit cost can be much higher than if tagging an entire collection, and failure of a
tag when the battery runs down is less critical if it is not part of the collection management
system.


5. Trial at the Petrie Museum
Initial investigations suggested that RFID tagging would be the best option for the Petrie
Museum, primarily because it does not require line of sight between tag and reader. However
on discussing the requirements with KTP Ltd, commercial suppliers of both RFID and
barcoding systems, it became apparent that RFID technology would not be suitable in its
current state, and they recommended that barcodes be used instead. KTP quoted a minimum
of 30 pence per RFID tag, and these were about the size of a credit card – considerably larger
than many of the objects. It was also unclear how well the system could handle scanning
multiple tags in close proximity. As there did not seem to be any other practical alternative to
consider, it was decided to carry out a trial with barcode tags. Details of the hardware used in
the trial are given in Appendix 1.

5.1 Barcode generation
Software for printing barcodes is available in the form of complete label design packages or
as fonts for use with other programs such as the Microsoft Office suite. Working
demonstration versions of both types can be downloaded from the web, and there are also a
few free fonts, mainly for the Code 39 symbology. Some printer manufacturers also supply a
limited range of barcode fonts bundled with their printers.

An evaluation copy of BarTender from Seagull Scientific (www.seagullscientific.com) was
used to print the first barcodes for the trial. BarTender is a feature-rich label design and print
program available in 3 editions according to the number of features enabled. The evaluation


                                                13
expired one month after installation, but before that it was used to print barcodes with
different symbologies and sizes. It was found that printing a 12 digit number in Code 39
produced a barcode twice as wide as the same number in Code 128C. Tag size must be
minimised because of the many small objects in proximity in the Petrie storage, therefore
Code 39 was ruled out despite its use being reported by several other museums. The Code
EAN13 barcode was about the same size as Code 128C, but the check digit was printed in the
human-readable number and could cause confusion if the number ever had to be typed rather
than scanned. If official EAN numbering was to be adopted then the museum would only
have control over the five digits that correspond to the product number, which could be too
restrictive and would not allow the Resource registration number to be included.

It was decided to use Code 128C barcodes for the next stage of the trial, and an evaluation
copy of the ID Automation Code 128 font package was installed (www.bizfonts.com). This
package allows barcodes to be printed from many applications and includes macros for use
with MS Office programs to calculate the check digit built in to the Code 128 symbology. The
evaluation version does not expire, but prints “DEMO” vertically in small type in the upper
part of some barcodes; these codes can still be scanned across the lower part and were quite
adequate for trial purposes. Sequences of barcodes were printed by generating the numbers in
an Excel spreadsheet and using this as the data source for MS Word mail merge. Printers
designed specifically for printing barcodes are available but not essential. Barcodes were
printed satisfactorily on an Epson EPL5700 laser printer at 600 dots per inch, but tests on an
HP 970Cxi inkjet printer rated at 1200 dpi produced symbols that did not scan so well at
small font sizes.




                     Figure 3. Ipaq PDA with SPS3000 scanner attached

5.2 PDA scanner
A survey of portable barcode readers showed several options for devices which might be
acceptable for visitors to carry around the museum and also be usable by staff for collection
management tasks. Symbol Inc., a major manufacturer of barcode scanners, produce the
SPS3000 range of expansion jackets which fit neatly onto Ipaq PDAs to add barcode reading
and/or wireless networking capabilities, and this combination matched the requirements
(Figure 3). An Ipaq H3950 was purchased together with the SPS3000 model which provides
both scanning and networking and includes a supplementary battery. Confusingly there is no
clear model numbering within the SPS3000 range, and it took two attempts for the supplier to
send the correct model. Scan drivers for the SPS3000 have to be downloaded from the
Symbol web site then installed on the Ipaq through its wired connection cradle, the device can
then decode all the common 1-D barcode symbologies. A program called Scanwedge included
with the drivers allows the scanner to be tested, displaying the contents of a barcode and its
symbology. By default the scanner is fired by pressing the button on the left side of the Ipaq,

                                              14
but the trigger can be changed to one of the buttons below the screen which some users may
find less awkward. A beep sounds and green light shows on a good read, while the laser
switches off after a few seconds if there is no read.

5.3 Wireless network
A set of wireless networking hardware was borrowed from UCL Network Services for
evaluation. This consisted of an access point and antenna for connection to the wired network
and two PCMCIA wireless network cards for use in laptop computers. It was found that a
single access point did not have the range to provide coverage throughout the museum,
although this was not essential for the trial. The strength of the wireless signal is reduced
when it passes through a wall or other solid obstacle, and the layout of the museum makes it
impossible to get unobstructed coverage from any single point. Another access point and two
USB wireless network adaptors have now been purchased to extend the area covered, but
parts of the galleries still have no signal.

5.4 PDA software
Hypertag Ltd were known to be using Ipaq PDAs for visitor information systems, and were
approached about the possibility of using their software with barcodes instead of the infra-red
tags they had worked with on other projects. After meeting to discuss requirements, it was
found that the cost of customising the Hypertag software would have taken a large part of the
trial budget and there would have been substantial further costs if adopted after the trial,
therefore this was not progressed further.

Communication by email with Forbes Hawkins, developer of the barcode system at Museum
Victoria, confirmed that it would be quite simple to set up an interface to the object
information already available on the Petrie Museum website using the Pocket Internet
Explorer (PIE) that comes with the Ipaq.

To avoid the possibility of disrupting the live museum website, a test copy was set up on a
separate PC running Windows 2000 Professional and Internet Information Services, together
with a copy of the MySQL database that holds object data extracted from the main Adlib
catalogue and is accessed using ODBC. Simplified HTML and ASP routines were created to
take account of the small screen on the Ipaq (320 x 240 pixels) and limitations of PIE such as
lack of support for multiple windows. A simple form was created to accept an object number
and link to a page that displayed the object image and description. A selection of UC numbers
were printed as barcodes to test scanning of a number into the HTML form. It was then
possible to scan one of these barcodes anywhere within range of the wireless network to
retrieve the object data. Once this basic capability had been proved to work, the framework
was established on which to develop the required functionality.

5.5 Laptop computer and hand held scanner
The Ipaq/SPS3000 has the advantage of being compact and easily portable, but is not very
convenient for data entry as characters have to be entered by tapping on a virtual keyboard
that displays on the screen when needed. A laptop computer running Windows XP
Professional was purchased and configured to connect to the wireless network and thus allow
authorized users to log in and access the Adlib database. A Zebex Alpha-50 trigger-operated
barcode reader was obtained on evaluation at the recommendation of suppliers Barcode
Solutions Ltd, and purchased after satisfactory testing (Figure 4). This lightweight laser reader
has a USB connector to attach to the laptop, and decoded barcode data appears as if typed on
the keyboard.




                                               15
                       Figure 4. Laptop computer and Alpha-50 scanner

5.6 Scanning tests
It was found that the beam from both the scanners had a wide spread that made it difficult to
scan the right barcode if several were close together. At a distance of 15cm the beam from the
Alpha-50 covers a width of 17.5 cm, and in tests with more than one barcode in the beam the
reader always decoded the rightmost one. Using black paper to block the sides of the laser
window proved that the scan width could be reduced to a certain extent without affecting its
ability to read the code.

Scanning distances were measured for different size barcodes to find a compromise between
small symbol size and reliable readability at a practical distance. The results are tabulated in
Appendix 2. For most font sizes the Alpha-50 has a substantially longer range, while
performance on sizes below 10 point was probably limited by the print quality. Font sizes
from 12 to 16 point appear to provide the most acceptable compromise between readability
and tag size.

The distance tests showed that if tags were placed next to objects in display cases many of
them would be out of scanning range, particularly from the Ipaq although most of the pottery
would also be out range of the Alpha-50. The number of small objects displayed close
together means that even placing barcode tags with those in range would be visually
distracting. An alternative was tried of placing a set of barcodes with small images of the
objects on the outside of a case, but this was also very obtrusive even for a few objects
(Figure 5).




                 Figure 5. Barcodes and images on the glass of a display case

With the density of the current displays, placing a barcode with every object where it can be
seen would have the unfortunate effect of making the museum look more like a warehouse. A


                                               16
solution would be to place barcodes within Ipaq range for selected items to enable visitors to
retrieve further information on those, while tags for the majority of the display could be
placed under the objects ready for scanning by a member of staff when an object is removed.
Another possibility would be for a visitor to scan a location barcode on a display shelf and
have the Ipaq display thumbnail images of objects recorded at that location, then selecting a
thumbnail could retrieve further details of that item.

One of the options for this project was to explore the possibility of being able to interface to
the UCL library barcode system to “issue” objects to internal researchers who are also
registered users of the library. It was found that neither of the scanners used for the trial were
able to read the library barcode symbology, therefore this was not pursued. It would be
possible for the museum to issue its own user tickets to record research use.


6. Recommendations and suggestions

   •   Barcoding every object and location would have real benefits for object tracking and
       administration, and it is recommended for that purpose.

   •   The benefits for visitor information are less obvious at this time, as there are major
       practical difficulties. Creating an electronic guidebook style system beyond the
       website catalogue data would be a major project in its own right. Such projects
       elsewhere have benefited from sponsorship and/or collaboration with major
       corporations, e.g. Hewlett Packard and the Exploratorium, IBM and the Cairo
       Museum.

   •   It is recommended that the Code 128C symbology is adopted because it encodes
       numbers in a very compact form with a built in check digit, and as it is widely used
       there should be no problem obtaining compatible scanners in the future.

   •   It would be impractical to encode object registration numbers into the barcodes. Item
       barcodes and location codes should use sequential numbers, using database tables to
       link these to UC numbers and storage location names. In both cases the number should
       be prefixed by 0117, the Petrie Museum registration number. Extra digits could be
       included for future use, e.g. to distinguish object codes from codes given to archives
       and photographs.

   •   To print tags in-house, purchase the full non-evaluation version of the ID Automation
       font package used during the trial. Available on-line, price US$139 for a single user.

   •   Consider purchasing a 1200 dpi laser printer which might give better barcode print
       quality and increased scanning range for small font sizes.

   •   Use archival quality self-adhesive labels, available from suppliers of conservation
       materials, to tag locations. Use acid-free archival card for object tags.

   •   Extend the wireless network to give coverage throughout the museum. This will
       require some experimentation to find optimum antenna locations. Consider purchasing
       equipment conforming to the faster IEEE 802.11g wireless standard once this has
       become established.




                                                17
   •   Stored objects are being separated and supported in Plastazote foam through an
       ongoing program of storage improvement. It will often be possible to cut slits in the
       foam to hold barcode tags, and it is suggested that barcoding implementation should
       begin with these drawers to gain experience with the system before tackling less well
       ordered areas. It would also be useful to provide feedback to those installing the foam
       if there are common problems in placing the tags.


7. Conclusion
Barcodes are a familiar and well-established technology, very widely used and low cost,
partly due to the adoption of global standards. However despite their widespread use in
industry and commerce, barcodes have been implemented in few museum collections.
Barcoding is not a perfect solution for machine-readable tagging of objects, the necessity for
line of sight between scanner and tag being the major disadvantage, but it seems to be the
most practical and affordable method currently available and will be particularly beneficial
for tracking the movement of objects during collection relocation. It is likely that further
development of RFID technology will lead to its greater commercial use and consequent
standardisation and cost reduction, and it will then be more appropriate for use in the
museum. The systematic tagging and recording of the collection with barcodes before the
museum is relocated will bring benefits which outweigh the disadvantages, and should make
any future changeover to a more advanced type of tag much less of an effort than the initial
implementation will be.


References

Adams Communications 2-D symbologies. http://www.adams1.com/pub/russadam/stack.html

Bergeron, A. 1999. Laser pointers. In message from K. Untch to the Conservation DistList
http://palimpsest.stanford.edu/byform/mailing-lists/cdl/1999/1420.html

EAN International. http://www.ean-int.org

Electronic Guidebook Project. http://www.exploratorium.edu/guidebook

Hawkins, F. 2002. Museum Victoria Collection Inventory System.
http://www.emuusers.org/MVCIS.asp

Helicon Talking Tags. http://www.helicon-cs.com

Jewess, C. 1995. The Ancient Monuments Laboratory Bar Code Location System.
http://www.eng-h.gov.uk/barcodes/

MDA Fact Sheets. http://www.mda.org

Picard, È. 1998. The Musée des arts et metiers reserve store, a research tool. La Revue 24,
Sept 1998.

Power, R. 2002. Barcoding for Museums. http://members.aol.com/oldtruth/bcindex.html

Schwarzer, M. 2001. Art & Gadgetry The future of the museum visit. Museum News
July/August 2001.


                                              18
Appendix 1: Equipment and software used for the trial

   •   Dell Inspiron 1100 laptop computer running Microsoft Windows XP Professional,
       fitted with a Cabletron Roamabout 802.11b wireless network card in the PCMCIA slot

   •   Zebex Premier Alpha-50 handheld laser barcode reader with USB interface cable

   •   Compaq Ipaq 3950 PDA running Windows CE

   •   Symbol SPS3000 add-on unit fitted to the Ipaq, combining barcode scanner and
       wireless network interface

   •   Cabletron Systems (now trading as Enterasys) Roamabout 802.11b wireless network
       access point connected to the museum wired network

   •   Actiontec 802.11b wireless network access point connected to the museum wired
       network

   •   Epson EPL-5700 600dpi laser printer (now superseded by 1200 dpi models in the
       Epson range)


Suppliers:

The Dell computer (approx £800) was purchased directly from Dell (http://www.dell.co.uk/)

The Ipaq pda (£405), SPS3000 scanner (£400) and Actiontec access point (£75)were
purchased from Dabs (http://www.dabs.com/uk/home.html)

The Alpha-50 reader (£175) was purchased from Barcode Solutions Co Ltd
(http://www.barcode-readers.co.uk/)

The Cabletron equipment was on loan and the laser printer was already in use at the museum
before the project started.

All of the items, or equipment with equivalent functionality, are available from many other
suppliers.

Most of the barcodes used during the trial were printed using demo versions of the BarTender
label design program (http://www.seagullscientific.com/) or Microsoft Word and Excel with
IDAutomation font software (http://www.idautomation.com/)




                                             19
Appendix 2: Barcode scanning distance table

The table shows maximum scan distances obtained when reading Code 128C barcodes with
the Alpha 50 and SPS3000 scanners. All barcodes encoded the same 12-digit number
011700018000 and were printed using ID Automation demo fonts sAdC128c and sAdC128d
on an Epson EPL-5700 laser printer. Scanning ranges were found to be identical for both
fonts, as expected since they differ only in height. Measurements were made (a) through air
only and (b) perpendicular to the glass into a museum visible storage drawer where the
barcode was 10cm below the glass.


                 Alpha 50                        SPS3000

Font     Air (cm)       Through           Air (cm)       Through
size                     glass                            glass

  8        8.5             -            unreadable          -
  9        7.0             -                7.0             -
 10        11.5           10.5             10.0             -
 11        16.5           16.0             11.5            10.5
 12        19.0           19.0             12.5            13.0
 14        23.0           22.0             16.5            15.5
 16        37.0           35.0             20.0            18.5
 18        37.5           36.0             25.0            20.0



             Barcode dimensions

 Font    Width      sAdC128c         sAdC128d
 size    (cm)         height           height

   8      1.40         0.40              0.70
   9      1.55         0.50              0.75
  10      1.80         0.55              0.85
  11      1.95         0.60              0.95
  12      2.10         0.65              1.05
  14      2.50         0.75              1.20
  16      2.90         0.85              1.35
  18      3.20         0.95              1.55

Barcode dimensions at a given font size will differ for other font producers.




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