I have become involved in producing large print maps through maintaining the Wiltshire pages of GENUKI. For each parish there is a description of the location as a distance and direction from a larger place, and genealogy information including a list of church records and indexes. Each parish page has a link to an Ordnance Survey map showing the location of the parish. The descriptions and other information as text on the web pages are accessible to blind or partially sighted people, but the linked OS maps are not. I therefore decided to provide basic maps in tactile and large print formats, to show the locations of main towns. The accompanying article Production of Tactile maps with Braille labels, published on web pages describes how I developed these, and the advice I received on tactile maps. My large print maps so far use the same graphics as the tactile maps, just changing the labels to be large print instead of Braille. Although there is a great deal of advice available on designing printed or web pages of text for people with visual disabilities, I have not found any general advice or guidelines on producing diagrams for people with visual disabilities. The main purpose of this article is to describe what I have done, and ask for comment and advice.
My background is in physics, computers, and genealogy, also having an interest in geography. I have no experience of blind or partially sighted people, or involvement in material or education for people with special needs. So I may have missed some advice which is well known to people in those fields.
I am aware that people with different visual disabilities have different requirements. Visual disabilities may blur the image, restrict the field of view, or change the appearance of colours. On web pages of text, there are guidelines for designing them so that people can alter the appearance to suit their preferences; some people may reverse or change the colours, others may increase the font size. On the printed page, there are guidelines, for example the RNIB "See it Right" booklets describe "Clear Print" recommending 14 point print, and "Large Print" 16 to 22 point. I have also used Effective Colour Contrast and Making Text Legible from Lighthouse International.
As I am producing tactile maps and large print maps, they start from the same basis. Braille characters are 24 point, so it is easiest for me to start with 24 point letters for large print.
I design the maps in CorelDraw and publish them as pdf files. It is very easy to "invert" the image: reverse all the colours - black to white and vice versa, colours to their complementaries. I could supply my CorelDraw files for people to download and modify to suit their preferences, but this would be complicated.
What I seek is a set of guidelines on producing diagrams for people with visual disabilities. For example:
I would also like examples of maps which are successful for a variety of visually disabled people, and comments from people with visual disabilities.
Labels are 2-letter abbreviations for towns, standard 3-letter abbreviations for counties, and are 24 point Arial. (In fact, the font is not embedded in the pdf file, so a user may get a similar substitute.)
On the large print map of Kent
On this map I have tried indicating grid lines every 10 km as thin light lines, but I considered that it made the roads and boundaries harder to see. I have now added another version with light tones as vertical bands, alternating every 10 km, with white horizontal dividers; this is particularly intended to help people who can only see part of the map at any one time.
On the map showing Kent and surrounding counties :
This map is to show the boundaries of Kent and surrounding counties, and also to show National Grid 100 km square TQ and identities of surrounding squares. Because London and Middlesex are relatively small areas, getting county labels into them determines the overall scale. Most county boundaries are black lines width 0.7 mm; but I have changed the London/Middlesex boundary to grey and allowed the letters to be immediately adjacent.
The "thin blue" lines to show the 100 km National Grid squares are 40% cyan, and are 0.18 mm wide. I don't consider this ideal, and would welcome examples of better combinations. Would it be better to give the grid square a light tone all over (e.g. 10% black)?
My files are in pdf format. This makes the files small, and gives very good definition, particularly of text. If there are other formats that would be preferable, or good alternatives, please let me know.
This page by David Hawgood was amended 21 April 2004 and validated by W3C Validator