What is it?

There are a lot of applications on websites for being able to tell where people are from their postcode. For example "Where is my nearest B&Q?". Unfortunately this data is expensive to licence (a few thousand pounds/year for a website). Free the postcode are doing a good job, but it is hard to contribute to their database as you need a GPS, so they have few postcodes.

Our goal is to collect postcode data by getting users to locate themselves on a map of the country. They need only give the first part of their postcode, and if we can collect locations for all of these parts then we can create a database that is good enough for many applications. We are also accepting complete postcodes and 'partial' postcodes including the number portion of the second half of the postcode, in order to improve our accuracy.

What licence does the data have?

The data will be will be in the public domain; consequently, users submitting data agree to their submission being in the public domain when they enter their postcode.

Will I get more junk mail if I enter my postcode?

No, we are just interested in where the postcode is. We don't collect your name or house number. Please see our privacy policy.

What maps are you using?

We have scans of out of copyright OS maps of England and Wales. You can register interest in future projects involving Scotland and Northern Ireland.

So can I do what I like with your scans/tiles?

No. The scans and tiles have been placed under a licence; they are not in the public domain.

Okay; I can use the tiles for some things; can I download the complete set?

Not yet. We need to make sure we've uncovered all the obvious flaws with the current tiles (eg human error in cropping and numbering the tiles) and have worked out an efficient distribution format. Let us know if you want to use the tiles; please don't try and crawl our tileserver to obtain the entire set.

Isn't orthowotsiting an old map hard?

Luckily we're going to work in the OSGB coordinate system that matches up with the grid lines on the map; this means we don't have to distort the maps too much. We also are not overly fussy about the accuracy, so this step can be done quickly.

Why don't you use maps created from OpenStreetMap data?

Because they are licensed under Creative Commons Share-alike licences, so we wouldn't be able to make our data public domain.

There are people who believe that locating a point on a map creates a derived work, and hence requires a licence. We don't want to be the first to prove them wrong in a court, as that will be pricy.

Also, the OpenStreetMap maps are not yet complete enough to achieve our goal of country-wide coverage.

Will this data be imported back into Free the Postcode?

Probably not directly. We are looking at the best way of presenting data from both projects whilst not polluting the Free the Postcode database with our lower accuracy data. We are importing Free the Postcode data into our database for display, but not re-exporting it currently.

If you are using scans of old maps, how accurate will the locations be?

Some of the scans are out by a degree or two but they are fairly good. We hope to be able to get better than 100 metres accuracy out of it in the end. This is more than good enough to locate a region as large as the first half of a postcode, and hopefully as much as the 'partial' postcodes described in the answer to 'What is it?' above.

My house isn't on a 1950s map

Find some local landmarks and guess where your house is. This is accurate enough for our purposes.

I know exactly where I am, and what my postcode is

If you have a GPS, enter your data into Free the Postcode and make the world a better place.

I can't seem to find a certain island on your overview map

We've put together a list of hard to find islands, so you might well be able to find it from there.

So, how do I use it?

Find your location on our map, click where your postcode is, enter the postcode, agreeing to release your data.

Psst, I have a copy of the codepoint database. Wanna look?

No thanks, we want free data so we don't have to keep paying the nice codepoint people.

Won't you drive codepoint out of business?

We don't think so. There are a lot of places where this level of accuracy just isn't enough. Those people will still have to pay until Free the Postcode improves its coverage.

The map doesn't join up.

Yes, it isn't perfect. The OS didn't publish a single map of the whole country, so you have to scan then stick together data from several maps. We don't really know how to correct it perfectly. It would be really cool if someone could write software to detect the gridlines and automatically cut the images up on the lines and make them square.

The wonkiness is so annoying it drives me mad, and I have experience of orthrectifying maps. Please let me straighten your maps.

Cool. Contact us, that would be great.

Why didn't you use proj/gdal?

Because we don't know how to work them. If you feel like improving how this works, let us know. Update: We do use proj for the postcode display.

Why don't you have good mapping data of Scotland and Northern Ireland?

While the Ordnance Survey did create the New Popular Edition maps of Scotland at 1 inch to the mile, these were never published, so we can't buy them to scan in. All we have been able to get is quarter inch to the mile maps, which don't fit into our tiling scheme, and are too small for finding postcodes on.

Scotland and Northern Ireland were included in the Ordnance Survey 7th Edition at 1 inch to the mile, but almost all of these maps remain in copyright for another few years, so we couldn't put them online.

If you do have free higher resolution images of either of Scotland or Northern Ireland (eg the 1920s Popular Edition, or the War Office Editions), then we would be very interested. Do please contact us if you have such maps.

If you would like to be notified when we do get out of copyright 1 inch to the mile maps of Scotland and Northern Ireland, please register your interest.

Who did the work?