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RE: Example: Real-time feed of satellite photos

From: Yvette P. Hoitink <y.p.hoitink@heritas.nl>
Date: Mon, 3 May 2004 19:14:26 +0200
To: "'WAI-GL'" <w3c-wai-gl@w3.org>
Message-Id: <20040503171333.B460AA0EFB@frink.w3.org>
John Slatin:


From: w3c-wai-gl-request@w3.org [mailto:w3c-wai-gl-request@w3.org] On Behalf
Of John M Slatin
Sent: maandag 3 mei 2004 17:42
To: w3c-wai-gl@w3.org
Subject: Example: Real-time feed of satellite photos

I received the following inquiry from someone who works at a state agency
here in Texas.  It presents an interesting challenge, and it seems like
something that might furnish a good example for us. I'm also curious to know
what solutions members of WCAG WG would propose in order to meet WCAG 2.0.
<begin query>
Our agency receives satellite photographs of Texas that are automatically
formatted into jpegs and loaded to our Web site. These images are real-time,
from one-hour to about 12-hours old. These are continually and automatically
updated on the site.

I have an opportunity to review these Web pages now because they are being
revised to add additional types of satellite photos. It's my job to make
recommendations regarding the content's usability and whether it meets state
Web site accessibility standards. 

On these pages, the user selects up to four different parameters (using drop
down lists) and then clicks a "display image" button. A jpeg is returned to
them in their browser. 

Since these images are automatically updated, alt text specific to each
photo can not be added. And I'm not really sure how they could be
descriptive enough, anyway. Besides, the photos are not presented inside Web
pages, they are just the jpeg files.

The state rule says we should provide an alternative format for pages that
are not accessible. I don't think that is possible in this case. Would you
suggest some disclaimer text on the page stating that these images are not

</end query>


Regardless of the realtime issue, I don't think you can give a description
of a satellite image that conveys all the information of the image.
Therefore, I would treat satellite images the same as images "designed to
create a specific sensory experience", requiring a text label or text
description but not a text equivalent. I do think this is stretching the
"designed to create a specific sensory experience " phrase a bit, so we may
need to revisit that wording. Unlike art, satellite images are not designed
to create a specific sensory experience but still require eyesight to do
them justice.
Since the images are selected based on parameters, they already have
meta-data associated with the image. Region, date and time would be likely
parameters, which I will use in this example.
They could use this meta-data to generate an HTML-page that includes the
satellite picture, using the metadata to create alt-text or a subscript. 
<img src="satellitepicture.jpg" alt="Satellite image of Wisconsin, 3 May
2005, 1:05 PM">. 
This would mean reprogramming the website so they do not open raw JPEG files
but use server-side scripting to generate an HTML page. It wouldn't require
a great effort since they already have to determine server-side what JPG to
open based on the selected parameters. The alt-text doesn't do the image
justice, but it's the best accessible way I can think of to present this web
Yvette Hoitink
Heritas, Enschede, the Netherlands
E-mail: y.p.hoitink@heritas.nl
WWW: http://www.heritas.nl
Received on Monday, 3 May 2004 13:13:33 UTC

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