Web Accessibility and Online GIS

March 19, 2007

Is it impossible?!

Online maps are visual, there is no getting round this basic premise. The use of a summary attribute for a map element in a page is the only thing I can think of that would be of any use. This works in the same was as an alt attribute for an image – screen readers will read this text out to users who have problems visual impairments.

As the majority of online mapping servers generate images as output there could probably be further development in customising the ALT attributes of these images to provide more detailed information of the current map state, so rather than alt=”A Map”, alt=”Map showing towns and major roads.” This alt text could be derived from visible layers, and the centre coordinates of the current map location.

I tried running one of my map URLs on the online validator at http://webxact.watchfire.com/ which tests “single pages of web content for quality, accessibility, and privacy issues.” It timed out…

http://wave.webaim.org/wave/Output.jsp performs similar checks..what can best be described as a mess was returned along with lots of “page not found errors.”

Fortunately clients do not seem to demand that accessibility standards are met for mapping pages, but with increasing legislation in many countries for websites to be usable by people with disabilites it is definitely an area that needs further work.


Posting Code on the Web

February 25, 2007

An important part of the blog will be code snippets. I thought it would be prettier if these snippets had the same nicely coloured syntax as I have in Visual Studio 2005. As will all things computer based things are never easy, and take time. After a good hour or so of messing around I found the following:

i) Copying and pasting to Word or Frontpage will convert the text to HTML (of a fashion..), but spacing and fonts are not retained, and the time spent cleaning up the code is probably equal to manually coding the HTML from scratch.

ii) I found a .NET macro that can be added to Visual Studio at Jeff Atwood’s blog – Coding Horror. This was a useful exercise in seeing how .NET macros could be written and run from Visual Studio, and what is involved in converting the text. Unfortunately when posting in the WordPress code box there were gaps appeared between code lines that had to be deleted manually. For large amounts of code this became somewhat annoying…

iii) The solution! A link from the page at Coding Horror suggested a Visual Studio Add-In created by Colin Coller at his blog Needs Improvement – the latest version can be found here. This Add-In creates a short cut when right clicking on selected code in Visual Studio, with a variety of options such as including code line numbers, and setting indent levels. The HTML can be pasted in WordPress and is displayed perfectly. The only minor problem seems to be if I then run the spell checker some spaces disappear. I’ll just have to be more careful when writing in futur.

Another interesting find, that is not really a requirement for the blog, is this web control. This allows a code text property to be set and when the web page is generated it can be rendered with syntax highlighting from a wide choice of programming languages.

    1     Public Sub VeryHappy()


    3         Dim LotsOfTimeSaved As Long = 10


    5         Try

    6             ‘copying and pasting

    7             LotsOfTimeSaved += 10

    8         Catch ex As Exception

    9             ‘not needed =)

   10         Finally

   11             ‘no need to search for another solution!

   12         End Try


   14     End Sub


February 20, 2007

I have recently downloaded, and been playing around with an OpenSource map renderer for the .Net 2.0 framework – SharpMap.

The development site can be found at http://www.codeplex.com/SharpMap. The development site is stored in CodePlex which is descriped in Wikipedia as a site website for OpenSource projects hosted by Microsoft providing “wiki pages, source control based on Team Foundation Server, discussion forums, issue tracking, project tagging, RSS support, statistics, and releases. ” This is the first time I have heard of CodePlex, but it is an interesting and well designed concept in itself.

SharpMap itself is very quick to install and comes with a set of demo pages that show some very fancy AJAX zooming, WMS capabilities, and symbology. The code classes themselves seem simple to use, and getting some of your own test data into a sample page was quick and easy. I hope to get a sample site together myself in the coming months, as it seems a very useful way to publish data without having to pay extortionate license fees in order to display geographic data – on a Windows server. In the meantime feast your eyes on this lavish screenshot…

SharpMap Rendering