Web technologies for accessible cartographyPresentation Transcript
Web Technologies for Accessible Cartography
Liddy Nevile Dr William Cartwright
The challenges ...
Spatial scientists and cartographers
aim to make spatial information more useful and ‘accessible’ to wider audiences
aim to make all information accessible to a wider range of audiences in a wider range of contexts
The symbiosis ...
Information encoding protocols XML , GML, SMIL, SVG, … ( OGC and W3C recommendations ) and
notions of 'content equivalence' and ‘multiple modalities’ and ‘device independence’ ( Accessibility principles)
brought together to make geospatial info more widely useable and accessible for all.
Typical use case:
Can’t use hands (or mouse or keyboard)
Screen reader output
Eg someone riding a tandem bicycle or someone using an assistive technology
My context - Quinkan Reserves
Requirements: location independent, device independent, language and literacy independent, ..
Needs: location, names, terrain info, weather, titles (real and native), attractions, history, access & IP rights, ...
(From the Quinkan Reserves Booklet of the Ang-Gnarra Corporation)
Quinkan Interpretive Centre
A Quinkan museum? Self-guided tours. How accessible would it be:
nearest city is 250 miles away
‘ exhibits’ are vulnerable
‘ floor space’ is 100 sq. miles
A virtual experience? How accessible could that be?
historically paper-based with inert images
Now ‘geographical visualisation’ or ‘interactive multimedia’ with
provision of power from author to user
data sets with access devices & interfaces for users to choose perspective, content and transformation.
A map may be a table of textual information, an image, a haptic representation, a sound presentation, and more...
Map-makers anticipate users’ needs
The choice must be available ‘just in case’ rather than ‘just in time’
Requirements for accessibility
Equivalent content, or
Content that is
Directly accessible, or
W3C recs for information representation
WAI recs for information accessibility (discovery and use)
OGC recs for geospatial information
Standards? Can these coalesce beneficially?
eXtensible Mark-up Language ( XML)
a meta-language to define and create new mark-up languages
promotes W3C's accessibility goals
separates structure and display
XML files not just presented but controlled by applications written in XML
XML vs. HTML
separation of data (within the XML file itself)
structure (as defined by the XSTL stylesheet) and
validation (by the DTD or schema)
A single XML file can contain multiple modal representations
<A_robustus_intro> <audio description> This page contains information relating to the fossils of Australopithesuc robustus. It shows an image of a skull specimen discovered in 1950 by Robert Broom showing a slight sagittal crest and large zygomatic arches that project forwards, hiding the sunken nasal area. </audio description> <large print> The above image shows the skull of Australopithecus robustus. Discovered in 1950 by Robert Broom this. Look at the distinctive features and note them. </large print> <standard> The above image shows the skull of Australopithesuc robustus. Discovered in 1950 by Robert Broom this. Look at the distinctive features and note them. </standard>
a single user is not presented with all three forms (normally, although it is possible) but rather with the form that suits some criteria specified by them, by their browser, or by their assistive technology access device.
**Note that the user has the final say.
In this case,
Technologies: Scalable Vector Graphics (SVG)
Yet another vector graphic format but W3C recommended and has accessibility qualities
Allows for text description of image
Includes metadata for whole and parts
Supports contextual zooming, etc
Synchronized Multimedia Integration Language (SMIL)
a clever set of controls for synchronising multimedia
is invaluable for bringing together the alternative representations that are used in the accessibility world
is interpreted by most assistive technology software and devices
eXtensible Stylesheet Language Transformations (XSLT)
XSL applications operate on XML stylesheets
can be selective with content, satisfying style sheets that define what is suitable for the user's access agent
uses applications to dynamically define content, its form, or its transformation
Scalable Vector Graphics
Text to produce images
Low-loss / high compression
2 or 3 dimensions
Elements and their relationship eg CAD
To produce SVG files
Server-side SVG generators are available:
AFP to SVG transcoder
CGM to SVG transcoder from IBM
Internet Mapper from XYZ Sistemas Industriales, S.A., which generates maps in SVG or HTML.
or convert XML to SVG using XSLT.
graphics can be exported from several graphics packages –
Adobe Illustrator and CorelDraw .
GE-Smallworld and SICAD GIS Internet map servers (range is growing).
Some printer drivers are available.
CSIRO (SVG viewer),
The University of Nottingham (postscript to SVG, Flash to SVG and a SVG-Perl library) and the
University of Tsukba (fdsSVG).
(See list at W3C site - http://w3.org/ )
SVG for cartographers
Traditional Raster images offer poor resolution, large file sizes, and too many server interactions for zoom, pan, etc.
Tax in Zurich, Schwyz and Zug http:// ww . karto . ethz . ch /teaching/ vtb _2001_ hilber _ ziegler /
It seems a short step, given the existing and emerging technologies, for cartographers to combine their exciting developments in geospatial visualisation with the techniques of accessibility to produce accessible cartography.
metadata should be standardised so equivalent alternative representations can be discovered and re-constructed or transformed for those with accessibility needs (widely described).
and, if it is in XML (RDF), it can be manipulated by XSLT and offered in a useful way to those who need it.