Friday 25 March 2011

Fairy land

Another string of pronouncements have been made on the Talk mailing list by the ODbL deniers about why OSM should not accept the new licence and contributor terms. Grant despairingly wonders why they should come to these conclusions.

People come to these conclusions because it suits their agenda, not because of the facts. Why let a carefully written licence and all of the discussions that have gone before get in the way of a good conspiracy theory? The world is full of conspiracy theorists and FUD mongers; the fact that OSM attracts them simply shows the project is big enough to attract the cranks as well as the serious.

Some people will always glaze over when confronted with a big blob of words, whether that's a licence agreement or something more important like an explanation of how dangerous radiation is. They then seem to go off into fairy land, inventing fearful scenarios and outcomes that are wrong.  Doing thought-experiments is a great way to test the limits of a licence, but you have to keep checking that you have not exceeded the bounds defined by the licence otherwise you end up in fairy land.

I fully and wholly respect anyone who has an objection to the licence change and who wants to use the CC-BY-SA licence as it is, I just haven't been convinced by their arguments. What I don't respect is the underhand way some people undermine the licence change process by spreading FUD and untruths about what it means and the way the project will work when the change is complete.I support the change to ODbL. I believe it will benefit OSM, but even ODbL is not powerful enough to drag everyone out of fairy land.

Thursday 24 March 2011


We've been working on addressing close to home. Bing aerial imagery came along and I realised that although Bing is not as good here as elsewhere, it is just about good enough to trace buildings. I traced a few buildings and then took the existing addressing and applied it to buildings. It was much better, so we gathered the remaining addresses for Swanland. I then tried to gather all the addresses for nearby Melton in a day (and didn't quite manage it). Then Blackadder announced he had completed a whole postcode, and I realised that I was more than halfway through HU14, so I just had to polish off North Ferriby. Just! What was I thinking about.

I decided to try Blackadder's scheme of drawing the gardens too. That means working out where the boundaries of private gardens are. This is harder to work out than it may seem. Some are masked by trees, some of the photography is a bit blurry and so on. Then there's the age of the photography - about ten years old. A lot has changed in ten years. I have had to use OS StreetView for a few areas where new housing has been built since the Bing photos were taken. I have tried to represent the differences between hedges, fences and walls as best as I could. I tried to take note of hedges or fences as we wandered around gathering the addresses.  My verdict on drawing gardens: DON'T. It is a pain and makes the difficult job a lot harder.

Gathering the addresses seems a bit easier, it's probably just that we can do it on auto-pilot. I draw the buildings as blanks before we gather the addresses, we can then write on the real addresses as we go round and sketch in any additions. It is still a lot of work. You can see more here.

I'm not doing any more addressing for a while, but I think I will do some more again. The prospect of gathering the addressing for the whole of Hull is overwhelming and would take years.

Friday 18 March 2011

Naming country roads

A lovely day tempted us out, first to do some jobs on the allotment, then trying to resolve a few names on the country roads. We found a couple of small residential roads missed on the first pass. We found two war memorials, a small church, some allotments and a village hall previously missed too.

Before we went out I spotted something we've seen before, or so I thought. There looked like a road name on OS locator that looked like it was really the name of a farm. There is a road called Highgate heading west out of Cherry Burton, which is well signed. OS Locator shows a small section of road called "Dunken Hill Highgate". I expected to find a farm called Dunken Hill and that the same mistake as we have seen before, that is an address has somehow become treated as a road name.

We found the farm called Dunken Hill, exactly as expected, but when I got home I looked at OS StreetView. It shows the road name as Dunken Hill (without the Highgate bit). It shows the farm name as Dunkenhill Farm. There is also a nearby area also labelled as Dunken Hill and the road crosses part of the edge of it. There were no signs, but I decided to accept the OS StreetView name. The OS Locator still seemed muddled and being different from OS StreetView is something that happens. If anyone knows better I will accept their wisdom or knowledge.

I'm not actually too bothered about some of these country road names, the roads are there, there are no houses or businesses on many of them except farms and they have names of their own. Many country roads have no name boards, so using the name to navigate isn't actually possible on the ground. Making sure the missing roads are added is much, much more useful, but hunting down road names can be an excuse for a pleasant ride out.

Monday 7 March 2011

Shared building, two streets

I have been gathering addresses and other detailed information for the villages that make up the postcode area HU14 - more of that soon. One thing I noticed in a few places is where a building that makes up a semi-detached house is on the corner of two streets and each house is on a different street. Having thought about it there is no real reason why both houses in a semi-detached should be on the same street, I just expected that they would be.

The highlighted houses in the picture are especially confusing because their numbers are so close, but one is on Riverview Avenue and the other on Southfield Drive.

Friday 4 March 2011

Who needs approval?

I have seen discussions about what tag to use since I first joined OSM and it's not always easy to understand. Some things seem obvious like tagging a road. It's a highway right, so highway= ... ? Residential is fairly easy (but is it a living_street), but is a substantial road a trunk road or a primary, or even a secondary? Is a small road a service road, a track, an unclassified or even a path?

How do I tag a church? Apparently it's not a church, it's a place or worship, so then it needs an extra religion tag to differentiate churches from temples from synagogues etc. Why not just tag it a church or a temple?

Areas of land are unfathomable. Some get the landuse tag, i.e. how the land is used such as retail or commercial. That makes sense, but then along comes landuse=grass. Not 'used for grazing' or 'used to suppress weeds', just landuse=grass. Hmmm, does that work?

So it seems that somewhere in the past a plan was devised to sort this out: an approval process. New tags would be proposed, discussed and commented upon and then voted on, so tags would be approved for use. Approved tags? What's that all about? There are no approved tags, anyone can use any tag that suits their purpose.  That's at the core of OSM and part of what makes OSM so successful.

Imagine what would happen if I couldn't use any tag I want to. Picture the scene: I come across something that is not in the list of approved tags. I want to add it to the map. I have two choices, 1) add it as something else that is in the approved list but that is not what I have seen or 2) I can walk on by and not add it until it is in the approved list.

Both of these are stupid: option 1) will show up as the wrong thing until the tag is approved. What if the tag is not approved? Will I remember to remove it? How will I feel about removing my hard-won object?

Option 2) is even worse. The object will not get into the map database. So not only will no one looking at the map or database know it is there, no one will know there is such a thing waiting to be added, so when (if) the tag is proposed no one will know how many of them there are waiting for the tag. Will I go back and add it to the database after the tag has been approved? Somehow I doubt it, more likely I would be fed up with the bureaucracy of the process and will have left the project to give my time to someone else.

Then there's the thorny question of who should be the one to approve these new tags? No one owns OSM, so there's no one to appoint an approver. How do I know what it is you are interested in or what you want the map to be about? I don't so doesn't that rule me out from approving your tags? That effectively rules everyone out from being the approver since no one can understand everyone's motivations, so next you need a committee to try to cover more interests. How big will the committee need to be? Who sits on the committee? Am I allowed to vote someone on/off it? Why? What gives me a vote? Do I get a vote because I have been in OSM for six days? Six months? What if I have only changed a single road name in that time? So maybe I get a vote because I've added a thousand nodes. I could just add loads of nodes into existing roads just to get my vote. Can I buy a vote in return for a donation of  ten dollars? What about 10,000 dollars?

So even if some sort of committee gets formed, how often do they meet? Will they need to get advice from other experts? So how long will it take to get a tag approved? When they do decide to turn down a tag will there be some sort of appeal process? What if that is challenged by a rich company that wants a tag approved and who has a large legal team?

How will people be bound by any of this? Clearly they will have to agree to this, so as well as signing up to a licence for the data, they will have to agree to be bound by the Approvals Committee. How many people will agree to that?!?

So the answer is simple. Allow people to use any tag they like and allow a process of natural selection to merge disparate tags together as a consensus develops. Publish a list of tags that are widely used based on statistics. A description of how people have chosen to use it would help other people decide if they want to use it too. A list of the tags supported by some of the main data consumers such as renderers and routers would help too.

If this the right way to do it, then why does the approval process exist? A very good question. I don't think it should not be there at all. Removing the process would remove the right of passage of creating a tag. It would stop the stupidity of someone creating a tag, getting it through the voting process by a few people voting to approve it and then claiming it is an approved tag and demanding it gets rendered even though it has hardly ever been used. It stops people voting for or against a new tag even though they have not used it, have no knowledge about the subject and only voted because someone invited them to do so on a mailing list.

So I do sometimes struggle to find the best tag to use, but I'm relaxed about that. I am not at all happy about the phoney, abused and irrelevant tag-approval process and I would like it to end now.