Web technologies for accessible cartography

Mapping Sciences Conference 2002

Web Technologies for Accessible Cartography

Liddy Nevile Dr William Cartwright

mailto:[email protected]

mailto:[email protected]


The challenges ...

Spatial scientists and cartographers

• aim to make spatial information more useful and ‘accessible’ to wider audiences

Accessibility experts

• 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.

http://www.w3.org/WAI/

http://www.w3.org/


Accessibility

Typical use case:

• Can’t use hands (or mouse or keyboard)

• Voice-only input

• 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?


Mapping Science

• 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.


Today,

• 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

• Alternative content

Content that is

• Directly accessible, or

• Compatibly accessible


The technologies

• 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_robustus_intro>


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 chunking

• 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

• Programmable

• Elements and their relationship eg CAD

• Accessible


To produce SVG files

• Creation

• Export

• Conversion


Creation• 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.


Export

• 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.


Conversion

• BlackDirt (WMF2SVG),

• 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.

• XML (SVG) images offer smaller files, sharper images, fewer transformation requests

• The range of transformations are all produced from a single data set


• vector graphic shapes (e.g., paths consisting of straight lines and curves), images and text

• dynamic and interactive

• clipping, masking and composing

• colour definition and fill

• symbol specification


• text placement (including text along-path)

• animation and motion-path animations.

• For data mining it also provides the additional functionality of being able to attach metadata to the SVG element as an attribute.


But• Source code cannot be protected

• Number of plug-ins is still small

• Some topology is missing

• Some limit to graphical symbolisation

• Some line styles re-assembled from 2 or more lines

Even so, interest in SVG is increasing.


Flash, PDF and ActiveX

• Currently most popular formats

• Not so interoperable

• Not accessible

• Require proprietary software

• Need multiple drawings for each view of map


We assert

that the languages can be used to provide alternative and equivalent representations for those with special accessibility needs

for the benefit of all. Greater choice of representation is generally beneficial - the information accessibility ramp.


Accessible geospatial visualisations

• Many of the above techniques considered essential for accessibility are available to cartographers

• The Open GIS Consortium is supporting this work in a number of ways


Geospatial Markup Language

• An interoperable XML language (esp. SVG)

• Has co-ord lists, points, lines, line strings, polygons, multi- points, lines and polygons

• Provides info about Spatial Reference System encoding, incl. map projection used, datum, spheroid and coordinates

• Allows for feature encoding


GML applications

• Open GIS Consortium part of WAP/W3C Workshop on in Nice, France, [Feb 2001]

• the OGC specs can meet the needs of WAP/W3C for mobile computing

• CSIRO (Simon Cox) is developing eXploration and Mining Markup Language (XMML) as an application of GML


Interoperable Geospatial Objects (Nolan et al, 1999)

• Use standardised metadata to have compatibility and comparability between different geospatial objects.

• ie objects that deal with the same geospatial object can be identified and their similarities/ differences identified.


Prototype mapping sites• Social Patterns of Vienna

http://ww.karto.ethz.ch/neumann/cartography/vienna

• OECD-Atlas of Europehttp://www.carto.net/papers/svg/eu/

• European/Swiss migrationhttp://ww.karto.ethz.ch/teaching/dip_2001_joray/

• Tax in Zurich, Schwyz and Zug http://ww.karto.ethz.ch/teaching/vtb_2001_hilber_ziegler/













http://www.carto.net/papers/svg/eu/







http://ww.karto.ethz.ch/teaching/dip_2001_joray/











http://ww.karto.ethz.ch/teaching/vtb_2001_hilber_ziegler/
















Conclusion

• 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.


And ...

• 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.

Web technologies for accessible cartography

Technology

Transcript of Web technologies for accessible cartography