Scores on the doors
When you go out to eat you want to know that the people preparing your food have a good standard of food hygiene. Across England, Northern Ireland, and Wales the Food Standards Agency collate hygiene ratings from local inspectors and publish them as an open dataset. It is a great, consistent, dataset and we already include extracts of it on our Data Mapper e.g. food hygiene ratings for Leeds.
To protect privacy, the user's location is not sent out of the page so our web server never knows the user's precise location. Instead, the user selects a local authority and we send every food establishment in that local authority to the browser. That means the user has to select the correct local authority and it is a bit slower to load initially but those are the trade-offs to protect privacy.
Update 2019-04-17: Having since added every Local Authority, the drop down list was proving to be a bit unweildly so we came up with a new method to auto-identify the Local Authority without sending the user's precise location to our server. We split the UK into roughly 55km (half degree) blocks and saved GeoJSON files containing the Local Authority boundaries in that block. Clicking on the "Use my location" button loads the boundaries for that block and, in the page, we then work out the Local Authority from the user's precise location and ask for everything in that Local Authority. That means our server still doesn't get to know the user's location better than about 55km or to Local Authority level.
Location, location, location
One problem I've noticed is that the location of the premises is sometimes off. That is because the FSA have determined the location by using the postcode centroid. This relies on the correct postcode being assigned and it also limits the accuracy with which a premises can be located. Sometimes a cafe/restaurant/pub might be listed up to 200m or so away from where it really is. It may be possible to improve locations by matching establishments to those included in Open Street Map data. However, the inconsistency of spellings and puncuation in both datasets will likely make that quite hard. It is something I'll try in the future.
The project currently covers Bradford, Calderdale, Kirklees, Leeds, Wakefield, Harrogate, and York. Update 2019-04-17: We have now added every Local Authority in the UK (England, Scotland, Wales and Northern Ireland).