Funded by:

© AHDS

     

What happens when you digitise?An introduction to some key themes

Alastair DunningArts and Humanities Data Service

http://ahds.ac.uk/

Think Digital:Best Practices for Digital Resources across the Cultural Heritage Sector

Funded by:

© AHDS

     

OverviewGeneral processesDigital objectsData models

Funded by:

© AHDS

     

Source Digitisation Resource

Funded by:

© AHDS

     e.g. William Shakespeare: The Complete Works

slides videotape

John Bright bust © Public Monuments and Sculpture Association

sculpture

text

performanceMark Rylance as Hamlet, Block/TIrmani, June 2000 © Donald Cooper

Source Digitisation Resource

Funded by:

© AHDS

     

digital audio/movie recording

scan/digital camera/3-D scan/OCR

item to digitise

digital object

Source Digitisation Resource

Funded by:

© AHDS

     

digital resource

Title: JOHN BRIGHT

Sculptor: Bruce-Joy, Albert

Type: Sculpture

Date Completed: 1890

Description: marble bust

Public Monuments and Sculpture Association collection available through AHDS

Visual Arts image catalogue: visualarts.ahds.ac.uk

Source Digitisation Resource

Funded by:

© AHDS

     

digital resource

As you like it, William Shakespeare.

Available as DOS ASCII Text (Especially converted for MS-DOS based machines.)

Search Results for William Shakespeare

http://ota.ahds.ac.uk/

Source Digitisation Resource

Funded by:

© AHDS

     

digital resource

September 4, 1995 ITN News At Ten

Actress Tilda Swinton becomes a living, sleeping, performance art exhibit for artist Cornelia Parker in an exhibition at London's Serpentine Gallery.

Newsfilm Online http://www.bufvc.ac.uk

Source Digitisation Resource

Funded by:

© AHDS

     

Elements of a digital resource

Users

Knowledge

Experience

Culture

Environment

HardwareSoftware(OS)(Network)

Digital ObjectsBinary Data

Data ModelsRelationships

• Users are the most important element

• Advice on hardware and software, objects and data models can be sought

• Fit for Purpose: Digital objects must be created with their intended use/purpose of paramount importance

Funded by:

© AHDS

     

Digital objects

• Text• Image• Time-based media

Funded by:

© AHDS

     

Digital objects - Text

• Text is data stored as a stream of characters (numbers, letters, etc.)– Text Transcription– OCR

Funded by:

© AHDS

     

Digital objects - Text

Text Transcription

Pros:• low overhead to start transcription • person, keyboard, document• hand-written documents can be transcribed• transcriber can follow complex disorganised documents

Cons:• slow and expensive• human error

© David Leach/Crafts Study Centre 2004

Funded by:

© AHDS

     

Digital objects - TextOptical Character Recognition

Pros:• automatic, suitable for digitising large numbers of documents• highly accurate for clean, clear type written documents• systematic errors can be easy to find and find

Cons:• current technology is very poor on hand-writing• complex document layout can become scrambled

5 S

Funded by:

© AHDS

     

Digital objects - Image

• Images are data understood as a spatial pattern or shape– bitmapped/raster images – vector spatial data

Funded by:

© AHDS

     

Digital objects - Bitmapped images• Bitmapped images are made up of

many pixels• Each pixel stores information about it’s

colour (RGB)• Pixels per inch (ppi) dictates amount of

visible information• The standard archival file format is

uncompressed TIFF v6

Funded by:

© AHDS

     

Fit for Purpose Capture

• National Gallery• Hi-res images• 20,000 * 20,000 pixels

• Old Bailey Online• Lower res images• 1,024 * 1,024 pixels

Funded by:

© AHDS

     

Digital objects - Bitmapped images

Good practice

• Check the optical resolution of the scanner• Avoid interpolated resolution• Capture master images at appropriate resolution and bit depth• Check scanning time• Record details of scanner/camera settings and any image editing• http://www.tasi.ac.uk

Scanning versus direct digital capture

• Always depends on the resource • Is there an analogue version of the resource?• Time – money – available skills• Image quality - colour fidelity

Funded by:

© AHDS

     

Digital objects - Vector images

x,y x,y,z

• A point represents an exact location in two or three dimensional space

• Two points define a line

• A series of connected lines define an area

Funded by:

© AHDS

     

Digital objects – Time-based media

• Time-based media– data understood as a sequence

through time– audio and video (multimedia)

Funded by:

© AHDS

     

Digital objects – Time-based media

• Audio– Moving from analogue to digital called sampling

– Frequency of sampling rates Hertz (Hz)

– Uncompressed digitisation 36kHz– .WAV and .AIF– MP3 offers good quality compressed

(lossy) files

Funded by:

© AHDS

     

Digital objects – Time-based media

• Video– Issue of file sizes and bandwidth– MPEG - The Motion Pictures Experts

Group standards are the most popular compression standards

– The three standards, MPEG-1, MPEG-2, MPEG-4

– Compression basically works by selecting key frames and only recording changes between the frames (but it gets a lot more complicated!)

Funded by:

© AHDS

     

Data models

• List, one item follows another

• Tree, each item can have several children

• Sets, items belong to one or more groups

• Geography/geometry, items are located using a co-ordinate system

Funded by:

© AHDS

     

Lists

e.g. spreadsheet

Funded by:

© AHDS

     

Trees and hierarchies

e.g. Text mark-up

<xml> <book title= “The Great Gatsby” author= “F. Scott Fitzgerald”> <chapter /> <page /> <sentence />

<word /> </book></xml>

Funded by:

© AHDS

     

Sets

e.g. Relational database

Table: art_work

Id no.ArtistTitleDescriptionSubjectMaterial

Table: image

Id no.File nameCreatorDateSize (pixels)ResolutionOrientation

one to many relationship, avoids redundancy, i.e. art workinformation is stored only once

Funded by:

© AHDS

     

Geography/geometry

• GIS (spatial) database

• The distribution of things upon the surface of the earth

• Maps and plans - Aerial photographs - Co-ordinate lists

Figure created by Peter Halls using data fromthe Cottam Project directed by Julian Richards. Image copyright © Archaeology Data Service.

Funded by:

© AHDS

     

Selecting your Data Model

• Consider how the original source material is organised

• What your users are familiar with• Fit for purpose• Seek specialist advice

Funded by:

© AHDS

     

Selecting software 1

• Avoid little-used software with proprietary features

• Select software that can perform the right tasks – e.g. Don’t use a word processor as a

spreadsheet– e.g. Don’t use a webpage editor as a

database

• Watch out for licencing costs

Funded by:

© AHDS

     

Selecting software 2• Do look for software with export and import

options.• Do look for software that supports important

standards. e.g.

How data is organised Data model

Important standards

trees mark-up XML (SGML)

sets relational databases

SQL

coordinates CAD or GIS

DXF,ESRI shape files

Funded by:

© AHDS

     

Summary

• A discussion of general processes including:– Source– Digitisation– Resource

• A brief overview of digital objects including:– Text– Image– Time-based media

• A look at data models and selecting software.