Use scanned image for tracing?

Hi all,

I’ve just joined OSM and would like to get involved. I live in a new housing development in Bristol, UK and would like to add my local roads and buildings.

I’ve got an Android phone and have downloaded OSMTracker. I’ll give that a go soon :slight_smile:

The developer also provides detailed maps of the area to be developed, which I currently have as pdf files. Can I use these as a background image in the editor to trace over? So far I’ve only played with the Potlatch editor, but if you’d recommend something else please let me know.

Generally, any tips or pointers would be appreciated.



Hi Stephen,

Using scanned images is possible, but pretty technical, and certainly needs some understanding of map projections. However, usually the bigger obstacle is that the map’s copyright will be owned by someone, and it’s important to get their permission before using it as a source (this is why using Google aerial photos is a no-no). Unfortunately in Britain it is highly likely that the developer’s map has significant elements of the detailed Ordnance Survey products, and that it was created using the OS GPS ground stations.

The route to working with scanned images is: a) georectify the image (tools such as GDAL, QGIS can do this); and b) get it accessible through a WMS or TMS server (there is a service called WHOOTS which does this for web accessible images). Normally this route is mainly used in OSM with public domain US military maps for humanitarian and crisis mapping. It has a steep learning curve. Editing then has to be done with one of the off-line editors (JOSM or Merkaator) as the on-line potlatch editor does not support WMS/TMS backgrounds.

Depending on the size of the area of the development, and whether you walk or cycle, it should take no more than a couple of hours to get decent GPS traces. Many people have just done things like vary the route to the paper shop, or where they walk the dog, and have thus collected the data incidentally. Personally I’d reckon this to be quite a bit quicker than trying to get permission & then re-jigging the map as a background.

If there are no other maps of the development then mapping it in OSM provides a great service for everyone in the area. An estate on the N. side of Cambridge was mapped some years ago and OSM was the only viable map for removal vans, taxi drivers, pizza delivery folk, and of course visiting friends and family. I know of similar stories in Ireland.

Some Bristol OSM contributors met-up recently: they ma be able to help. Check the OSM wiki Bristol page.

Best wishes,


Hi SK53

Thanks for getting back to me :slight_smile:

The GPS track does sound like the best solution. I tried out OSMTracker this morning, but it didn’t get a lock before I had to go to work. I’ll keep playing and hopefully be able to use that to get the roads in.

The main thing I wanted to be able to do with the scanned map was to mark the individual houses on. As you mentioned, I thought this would be useful for deliveries etc. Is there an easier way to do this? I have a pretty good relationship with the developer and think I’d stand a good chance of getting permission to use the map, but I think I’d need a more detailed guide on how to use the image.

Thanks for pointing me to the Bristol page on the wiki. I’ll see if I can get in touch with someone local as well.


Houses not yet on an OSGB map are unlikely to be copyright by them (but one can never be sure :-)).

Make sure the developer understands the implications of the OSM licenses CC-BY-SA & ODbL, and that you get the relevant permission. I don’t see problems with this: there’s a win for the developer in that the properties are on the map, and many of the materials are openly available as site marketing material and so on. You both need to be aware of what might have been based on OSGB stuff.

If you have a really good relationship with the developer you might ask for the house outlines in a vector format (ESRI Shapefiles are far & away the easiest to deal with). It’s a lot easier to re-project a shapefile & convert it into an OSM file suitable for importing than rectifying images.

There are also programs available which pull shapes out of PDF files (used with the French Land Registry data), but I dont pretend to know how they work or how you deal with projections with them.

As for getting a lock, even with my dedicated GPS devices I tend to leave them out in the open for 10 minutes before mapping: I get better results. Many gadgets are also sensitive to how they are held & orientation.

Hi Stephen,

I normally use a windows mobile 9.5 phone for logging but I also have an android device. It usually refuses to get a fix (however long I leave it) unless it is connected to the internet via either GPRS or wi-fi. So what I do is connect to the internet, fire up the GPS wait a small amount of time for the fix, then disconnect from the internet.