Free the postcode lite

What is it?

There are a lot of uses 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 I believe). Free the postcode are doing a very good job, but it is hard to contribute to their database as you need a GPS so they have few postcodes.

The idea 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 a lot of web purposes.

What licence will the data have?

It will be public domain. Users will have to place their data in the public domain.

What maps will you use?

We have scans of out of copyright OS maps of the whole country.

Isn't orthowotsiting an old map hard?

Luckily we're going to work in the OSGB coordinate system that matches up with the 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. I don't want to be the first to prove them wrong in a court as that will be pricy.

Will this data be imported back into Free the Postcode?

It might be, that will depend on someone working out how to store partial postcode data in Free the Postcode.

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 pretty good. We hope to be able to get better than 100yds accuracy out of it in the end. This is more than good enough to locate a reagion as large as the first half of a postcode.

My house isn't on a 1950s map

Find some local landmarks, 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.

Why doesn't it work yet?

We're still thinking about how this will work, and processing the maps so we can use them on the web.

So, how will I work 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.

Yeah, 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. I 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 I don't know how to work them. Feel like improving how this works, let me know.

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

I don't think they were part of the new popular edition at 1inch to the mile. If you have free higher res images of either of these places (we only have quarter inch to the mile) then we might be interested in them.

Who did the work?