A meaningful share of Terravek's customers are public sector bodies with a legal obligation to buy accessible software. That is what got accessibility onto our roadmap. It is not what has kept it there.
The obvious work was the obvious work: contrast ratios, focus indicators, semantic markup, keyboard navigation through the whole application including the map. Tedious, well-documented, mostly mechanical.
The interesting work was the map itself. A geospatial viewer is a fundamentally visual artefact and there is no honest way to make a raster image accessible to a screen reader. What you can do is make everything around it accessible, and provide the underlying measurements in a form that does not require seeing the picture — a queryable table of the features, their attributes and their locations.
Building that turned out to be useful to a great many sighted users too. It is now the fastest way for anyone to answer 'which spans breached clearance this cycle', and it was built for screen reader users.
We are at 91% of AA success criteria and publishing the gap list. The remaining items are mostly in third-party components we are replacing.