Donald Noble’s Site

It is possible to use the Ordnance Survey Open Data 1 to 250,000 raster maps as a background layer in JOSM. However, the positional accuracy of this scale of map is limited. This could also apply to the StreetView tiles, but they are readily available as a WMS layer, which is probably preferable.

The OS tiles are in the OSGB co-ordinate system, but OSM uses WGS84. However, there is a plugin that can fix this, and re-project the tiles in the correct location.

Firstly you need to register and download the tiles from the OS, if you do not have access to them. This is free, but can take a while. Once you have saved these to your computer, move the TFW world files from georeferencing files/TFW/ into the main folder with the TIF images.

Then install the Import Image Plugin for JOSM, and restart as required.

To import a tile, select ‘Import image’ from the file menu; browse to and select the required TIF image (with the TFW file in the same folder). This should be imported to the default reference system (which will be wrong, but that is changed later).

Once the image is imported, right click it in the Layers panel, select ‘Layer Properties’ then the ‘Source Reference System’ tab. Type EPSG:27700 in the search field, which should give “OSGB 1936 / British National Grid [ESPG:27700]”. You will probably want to ‘Set as Default’ so that this step doesn’t need to be repeated. But you also need to click ‘Apply Default’ at the top to re-project the image, this isn’t done when setting the default.

This should give the OS 250k raster tiles as a background layer, in the correct location with standard OSM data. Additional tiles have to be imported as separate layers, and need to be toggled when tracing at boundaries, because the images have been rotated and scaled as part of the re-projection.

addenda This should also work for any other image map using UK National Grid, where you have (or can create) the appropriate world file for the extents of the map.

Constantly typing source: OS_OpenData_StreetView when editing OSM was becoming tiresome. Therefore I hacked together a quick sources preset based on one for Spain by user Sanchi. Perhaps this will be useful for others editing OSM in the UK using JOSM.

With one or more nodes or ways selected in JOSM, simply click on “Data Source” to open a dialogue box to quickly add in the source(s) used.

To install, open the JOSM preferences and select “Map Settings” (the 3rd tab down) and then the “Tagging Presets” tab. Click the + to the right of Active Presets, and enter a name such as “Data Source UK” and the URL http://drnoble.co.uk/files/OSM/Presets_Data_Source_UK.xml. This should be available after restarting JOSM.

You may wish to add a shortcut icon to the toolbar, rather than using the menu item each time.

Version History

• 0.3 (2012-01-02) Current version added ‘OS_OpenData_VectorMapDistrict’ and note/fixme fields
• 0.2 (2011-12-28) added ‘local knowledge’ item
• 0.1 (2011-10-15) first version

I have done most of my Open Street Map editing using the free JOSM Editor, as I feel it has a number of advantages over the default, Flash-based, Potlatch editor built into the website. The feature I use most is the various background image layers, but also being able to quickly loading my GPS tracks and support for other plugins are useful too.

JOSM Imagery Layers

When editing, primarily I’ll use Bing aerial imagery (also available in Potlatch) to help align my GPS tracks and photos. However, in areas where high resolution imagery is not available, I can switch to the Ordnance Survey Open Data Street View layer¹.

There are also a number of older maps which are now out of copyright, and so features such as hills (which don’t change much) can be added to OSM. They can also be useful for checking routes of old railways etc., although the alignment can easily be 50-100m out. There is a list of old map sources on the OSM wiki — however, coverage is incomplete, and sometimes the servers are not available for whatever reason.

When editing in hilly region, I sometimes find the hill shading incorporated into the cycle map useful; and again, this can be loaded as a background layer (although it can also be a bit slow to load at times). Finally, I also occasionally load the OSM tiles as a background, which at first seems counterintuitive, but can be useful.

There is also support for displaying multiple layers at once, being able to alter the transparency of each. But this often becomes very confusing, as it is not always apparent which layer something is from.

GPS Tracks

JOSM can directly load GPX files, as well as (optionally) downloading other GPS tracks uploaded tot he OSM website. I usually change the colour of my tracks, and set them as the top layer, so that they stand out against the other tracks and features.

JOSM Plugins

I have installed quite a few of the available plugins for JOSM, but the two I find most useful are:

Buildings Tools which lets you quickly draw rectangular buildings. I have configured the preferences to automatically set source="survey;bing" as this is usually the case. Complex buildings can be drawn in parts, and made into one using the shift-J join shortcut. When combined with the feature to constrain the geometry to selected ways, this is especially useful.

Improve Way Accuracy lets you realign a series of nodes with fewer clicks—especially handy when using a trackpad. Simply select the way, press K, and click to realign. ctrl+click adds a new point, and shift-click locks the movement of a specific node.

JOSM Presets

Having a much wider series of tagging presets built into the program speeds up editing IMO. Although the grouping of them sometimes seems counterintuitive, so I added the preset search dialogue button to my main toolbar.

You can also install additional presets for the types of things you are editing (such as Skiing). The One click presets are especially useful for tunnels and bridges.

I have also developed hacked together a preset for source tagging based on another similar preset for Spain. See separate post on this

I’m sure there are loads of other useful plugins/presets etc. out there that I am not aware of, but these are the ones I have been using to date.

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¹ A nominally 1:10,000 series of maps, not to be confused with Google’s street-level photography.

I finally bought myself a DSLR camera in the spring, and I have taken approximately 6100 photos with it since then, plus another 1700 during the year with my old camera, and a few hundred on my phone… However, my top 10 of the year were all taken with the new camera.

Looking back over those that are on Flickr, there is an obvious pattern. Most of my top 10 are either completely monochrome or simple tones, and are mainly closely cropped details. There are exceptions to this, but not many. Surprisingly perhaps, they are not all square format, and I have been processing far fewer panoramic shots this year.

My top three are as follows, and you can view my top 25 on Flickr

Iris Leaves

Glasgow Botanics Station

Orange Chain

Over the past few months I have been getting involved with the OpenStreetMap project — a Wikipedia style map that anyone can edit, and use for whatever they want.

I had downloaded a few map apps for my iPhone, which used OSM as a background. I spotted a few errors, so looked into how to correct them.

I had looked at OSM a few years ago, when it was just a series of straight line roads connecting the major towns. Since then it has improved significantly, and now has most roads accurately located, as well as a multitude of minor tracks and paths that are not on other maps.

Over the course of this year, I have noticed the map grow, with people adding and tweaking things here and there. For example, the routes of the new M80 and M74 appeared as they were constructed, and were changed to live motorways on the day they opened. Six months later, they are still not on Google, Bing, or Yahoo Maps; and thus any of the services that use these.

While the motorway network is a more obvious differentiator — I actually think that the local addition of tracks and paths, for walking and cycling, is the biggest asset of OSM. The likes of the Ordnance Survey, Google, and Navteq will update their maps of the motorways at some point. But they are unlikely to add the minor paths that make up an interesting bike ride, or a great walking shortcut.

As for why I contribute my time to this project, it is an interesting project, that could — in the same way as Wikipedia — become a de-facto standard for maps in a few years time. If everyone (or at least a reasonable number of people) add there own favourite shortcuts and routes, they will all be mapped for everyone to use.

I will post more on the editing I’ve done, the tools I’ve used, and the outputs I’ve seen in further entries. At some indefinite point… probably!