Potlatch – the OpenStreetMap editor

First post on this blog for a while – not so much as a result of inactivity, but rather, because OpenStreetMap has just moved to API 0.6 and that’s meant a lot of work for Potlatch to keep up.

Most of this is behind the scenes and won’t make any visible difference to the user. In particular, the “version number” of each node and way is now communicated back and forth between Potlatch and the server, to make sure that changes can’t get out of sync if two people are editing the same thing at once. It might sound simple, but it’s been quite a lot of work to mash that into Potlatch.

Then there was the problem where the server started storing relation members as ‘Node’, ‘Way’ and ‘Relation’ – rather than ‘node’, ‘way’, and ‘relation’. It’s at times like this that you want to hit the computer round the head and say “look, you know what I mean, just get on with it”.

However, it’s not all boring internal stuff, so here are some of the changes in the most recent Potlatch – 0.11. There’ve been various improvements over the last week so if you didn’t see them to begin with, look again; and there’ll continue to be more tweaks over the days and weeks to come.

Speed

Here’s the really good news!

Redrawing the map is now a lot faster in areas with relations – which is a lot of the world. In brief, when Potlatch 0.10 (and earlier) drew a way, it would look through all the loaded relations to see which ones the way was in. And then it would do the same for every node on the way.

It doesn’t do that any more. Each way now has a list of the relation it’s in; so does each node. The difference this makes to the speed is immense.

There are a couple of other speed improvements, too. Of course, Potlatch is still dependent on the speed at which the server sends map data; the new server has improved this, but times when lots of people are editing are still best avoided if you can.

Changesets

An improvement in OpenStreetMap’s new API is that your work is grouped into “changesets” – a grouping of all the editing you do in one session. You can add a comment to the changeset, so that others can see what you did easily. To add a comment using Potlatch, once you’ve finished your edits, press ‘C’. Type your comment and click Ok.

This feature could be (and will be) further refined but it’s a good start for now.

“You have unsaved changes”

Firefox and Safari users have long been prompted if they close Potlatch while changes are unsaved, but this now works for Internet Explorer users, too.

History

The history feature (‘H’) is smarter, and can now detect small changes – typically just moving a node or two – made in other editors.

In particular, it now looks at the history of all the nodes in a way, not just the way itself. As a related improvement, Potlatch no longer saves a new version of the way itself to the database if only the nodes have changed.

Background layers

The options dialogue box has been improved for a clearer layout of background layers.

In addition, you can specify your own, custom layer if you have a set of ‘900913’ (spherical Mercator) tiles somewhere on the web. To do this, specify the full URL (including http://), replacing the z, y and x co-ordinates – in that order – with exclamation marks. For example, http://npe.openstreetmap.org/!/!/!.png – but don’t try to trace from Google, it won’t let you. (This was actually added in 0.10f.)

Error messages

Error messages from the OSM server are now shown to the user, rather than just blinking the warning icon. So if there’s a problem, you get to know about it (and can e-mail me in case it indicates a bug in Potlatch!).

Most of the Potlatch development work recently has been updating it to cope with API 0.6, which is why there’s nothing very much visible right now.

But, hoorah hoorah, a slightly updated new version is now live.

The main change is that there’s more presets. Lots of them: addressing, landmarks, sports, and so on. Better still, the preset ‘group’ icon doesn’t reset itself every single time, so you don’t have to keep paging through. (Funnily enough, the hardest work was drawing the icons. I’m still not that happy with the lighthouse for ‘landmark’ – it’s ok if you know what it is, but probably not otherwise…)

Another change that UK mappers will appreciate is that NPE is now offered at zoom levels 13 and 15, not just 14. (Thanks to TomH for this one.)

And, as ever, there’s a couple of little fixes in there. Nothing major enough to merit a new version number though!

NPE coverage is now complete for England & Wales at zoom level 14. Just select Potlatch’s out-of-copyright map layer and it’s all there. Zoom levels 13 and 15 will follow next week courtesy of Tom Hughes.

Potlatch’s out-of-copyright layer now has New Popular Edition maps for the whole of the south of England.

That means I’ve now finished rectifying all the NPE scans, though a few areas in the North haven’t uploaded, and there are a bunch of rogue tiles hither and thither (e.g. Cardiff, Somerset). I’ve started work on fixing those and they’ll be done in forthcoming weeks.

The Scottish Popular Edition, with Mike Calder’s excellent scans, is the next challenge! At Andy Allan’s suggestion I think it might be worth opening this up for people to help with the rectification and will be considering how best to do this.

The latest Potlatch is now live.

The main new feature is a super new “parallel path” feature, which will create a way at a given offset – in metres – from another one. So if you’ve driven along one carriageway of a motorway, but not the other, you can still map both – just draw the first one, then create a parallel path at the right offset.

To use it, select the way, then press ‘P’ for parallel. Potlatch will ask you what offset to use – you can choose from a handful of presets, or enter your own. Click ‘Ok’ and two offset ways will be created, one on either side. Delete the one you don’t want, and unlock (click the padlock) the one you do – after adding intersections, tags and so on, of course.

A few other changes:

• The ‘loading ways’ display (top right) now tells you whether it’s saving data, too.
• When you zoom in/out, ways are redrawn (at the new width) gradually, not all at once. This means that Flash Player won’t seem to hang every time you zoom.
• A new option, “Highlight unnamed roads”, will show any unnamed highways with a red border (casing) – particularly useful in cities where people have traced from Yahoo aerial imagery. It’s just like the NoName layer on the static map.

All of Northumbria and Cumbria are now on Potlatch’s NPE layer (at zoom level 14, of course) – plus Doncaster which was accidentally missed off the last release.

The two remaining gaps are a “central belt” across Northern England (the Pennines, Yorkshire etc.), and the South-East. (Scotland will be done later.)