General Mapping tips for creating buildings and houses in JOSM

• Alignment: After downloading your aerial imagery (e.g. Bing, Esri), first hide any data layers to avoid confusion, then show the OSMUK Cadastral Parcels layer (Click Imagery > Imagery not matching any other category > OSMUK Cadastral Parcels). Then create an offset on your aerial imagery (e.g. Right-click on Bing layer > Offset > New offset) and drag the imagery around in the main window, trying to match to the ground rather than roofs. Click Okay. Now you can show the data layer again and (optionally) hide the Cadastral Parcels.
• The cadastral Parcels layer is not always 100% accurate, but you can use Cadastral Parcels to give you a good idea of whether buildings should be split. It’s a good way of checking how many houses there are in a terrace, for example. You can then verify and check these splits when you survey on the ground.
• Use the buildings tool (B) to create square buildings easily, extrude areas by using the ‘Create Areas’ tool (X), double clicking to add points and dragging to extrude.
• For terraces, if it’s a simple rectangular shape, create a single building for the terrace, then split it into the correct number of houses using ‘Terrace a house’ function (Shift+T).
• For complicated, (e.g. mirrored, then repeating, turn-of-the-century terrace houses), it’s sometimes easier to create a single house first, then select the outline, then add to the selection two points along the mirror line, then Ctrl+C, then ctrl+alt+V, alt+shift+S. This will create a mirrored version along the mirror line, but some nodes will be duplicated. Then select each pair of duplicated notes (one pair at a time, I usually use lasso select mode for this), then press M to merge them. Repeat this process as necessary until you have the entire terrace of separated, identical houses. This method also works well for semi-detached pairs of houses. You can then duplicate these pairs of houses Ctrl+D, moving and rotating as needed (ctrl+shift+drag).

Recommendations for gathering house numbers, names, address info and other details for mapping

• In person visits, surveying on the ground. If, before doing this, you have already created the houses and marked them as building=house, using an app called StreetComplete will prompt you for house numbers. You can do all of these while on the survey, but it’s usually quicker to mark the extremes and any abnormalities, then fill the rest in later in JOSM. E.g. On a road with houses from 2-86, while surveying on the ground, mark 2, 86 and anything unusual, such as 16A, 16B, or extra houses with names that have been built in gaps between other houses. Look out for houses converted to flats which may have multiple addresses. It’s also a good idea to mark all houses at junctions, since it’s sometimes not obvious later on which road a specific house is on. One more thing to look out for is whether or not a road has a house number 13. Some do include 13, but often, presumably due to superstition making a house number slightly less desirable, developers will call the house 11A, 12A, 14A or sometimes omit 13 completely.

• Use Kartaview and Mapillary imagery. There are JOSM plugins available too.

• Create your own Kartaview or preferably, Mapillary imagery using the corresponding apps, and use it later. Doing this can help others in future too, even if they’re looking for other street-side features, so please consider using one of these, especially Mapillary as it’s the one most mappers tend to use. This is possible while driving (phone in cradle) or while walking or cycling. If you’re driving, and if your main interest is collecting house numbers and names, consider using your phone in a cradle attached to a side window rather than the front. You’d be surprised how good this can be. From my personal experience, phones featuring cameras with built in optical image stabilisation tend to fare much better on bumpy roads than those which don’t. If you’re walking and using the Mapillary app, remember it’s also possible to manually trigger a capture, to make sure a detail has been captured, rather than waiting for the automatic periodic captures.

• If driving, you could also use a dash-cam to record video footage of the houses. You can view this footage later and make notes.

• If your dash-cam has a microphone and you are on a very very quiet road, it might be possible to stop the vehicle in a safe place and make audio notes to remind yourself of important details later.

• If your Dash-Cam includes a GPS, this footage can also be uploaded to Mapillary directly for the benefit of yourself and others. If you’re in the market for buying a dash-cam, it’s possible to get ones with rear-facing cameras too, and some even offer the option for a third camera. Usually these 3 cameras would be designed for ‘front’, ‘rear’ and ‘internal’ use, but you can always point them out of side windows to see what’s on the left and right, or left and rear, or some other combination. Usually if these are wired correctly they will record to the SD card in the main camera, and if it has a GPS module, all 2 or all 3 sets of videos will be GPS tagged. This is very useful for Mapillary, for your own use, and to help others.

• Consider getting a 360 camera compatible with Mapillary and attaching it to your car, or walking around with it as you go. I’ve never tried this, but some do it. Keep in mind that 360 cameras often record lower resolution imagery, since the entire field of view needs to be mapped equirectangularly, so zooming in to house numbers might not be quite as successful as you might imagine, unless the camera is very high resolution. Try to find sample recordings from other people and determine if it would work successfully for your own intended use.

• Please be extremely careful if recording for the purpose of mapping while driving. Road safety is of far more importance than mapping. Please comply with all road safety laws and recommendations in your country, and exercise common sense.

• If driving, you could use a phone camera in a cradle (preferably with the screen off to avoid distraction and save power) to record video with possible audio notes, as above. Again, only do this if it is allowed in your country, and exercise due caution at all times.

• If walking, you can similarly use your phone or other device to record video along with audio and explain what you can see (E.g. “Terrace from junction with Sycamore Road, from left to right is 18, 20, 22, 24, 26, 28” or “red door is 33A and 33B, white door is 31”). Or you can use your phone to add to Mapillary or Kartaview, remembering these won’t record audio.

• There are probably other combinations of these you could imagine and use yourself. You could even print the map out, labelling and adding notes as you go. Don’t forget you can make notes of amenities such as amenity=waste_basket along the way. It’s also a helpful to take photos of things like Post Boxes, noting their collection times, and add these to OSM too.

• You could also encourage your friends to download and use simple OSM data-entry apps like StreetComplete. As mentioned earlier, if a building is marked as “building=house”, it will prompt for a house number on StreetComplete.

Requesting permission to use data from other maps and data sources

As OSM mappers, we all know we can’t use other peoples’ maps or data, because of copyright. But don’t forget, it is perfectly acceptable to any maps or data, even if copyright usually applies, IF YOU RECEIVE PERMISSION TO DO SO. How can this apply to OSM?

I have recently approached a number of housing developers in my local area who have excellent, detailed site plans of current, past and future housing developments on their websites. Without asking permission, we cannot make use of these maps, but I recently tried the following: I composed a brief email explaining my voluntary work for OSM and what OSM is. I then asked if it would be ok for me to copy details from specific maps on their website to help update OSM to help local communities. I then briefly mention how the information shown on their maps could helps couriers, cyclists (they often show cycle paths), pedestrians, motorists, etc. Most housing developers I’ve approached have been very happy for me to use their map data. I’ve technically never had a refusal, but some developers never replied, meaning I couldn’t use their maps.

Asking permission can also apply to other data sources, not just new housing developments. It’s just what I have most experience of personally. Another example might be to request permission from charities regarding the location of specific objects such as defibrillators and bleed control kits in a town, or other good sources of what would be considered ‘local knowledge’ if those individuals were to contribute to OSM themselves. Many people aren’t aware of the existence of OSM, even if they use it every day through other services. When requesting permission, I always try to email, because when they reply, you then have evidence of the granted permission for future reference, just in case it was ever queried. It also helps you know exactly what data they’re giving you permission to use.

Once permission is granted, it’s then just a matter of taking the (usually JPEG) file from their website into JOSM and rotating/scaling it to the correct location and orientation. This often requires trying to match the site plans to existing OSM map features and/or satellite imagery. It can be tricky sometimes, but it’s usually possible. JOSM has all the tools needed to align these maps accurately.

Housing Developers’ maps are a really valuable resource. The great thing about these maps is that they often include details and features that are almost impossible to get from aerial imagery. They also show where terraces are split into individual houses, exactly which buildings are garages, terraced houses, detached or semi-detached houses, electricity substations, etc, as well as attenuation ponds and similar features, and the location of cycle paths vs footpaths. It could also be available months or even years before aerial imagery is updated to include these developments.

A few points of caution, though. Just be aware that in some, very rare cases these plans are not followed exactly, and houses are built slightly differently than shown. From my experience, this is quite rare.

Also, please don’t be fooled by the numbering of most development plans. These are almost always plot numbers, not the final house numbers on the street! From my own experience, the street names can also, very occasionally, be subject to change.

(As I write this, I don’t have JOSM open to explain which tools I use for imagery alignment. I will try to add this later. Please send me a message if you need these instructions and I’ll try to add it soon.)

UK Post Codes

For Post Codes, things become a little more complicated, but this info can usually be discovered without too much effort for most houses.

• The Code Point Open Dataset (https://www.data.gov.uk/dataset/c1e0176d-59fb-4a8c-92c9-c8b376a80687/code-point-open), better known to most OSM users as Post-Code Centroids can be added as an overlay on JOSM easily. Please see this guide here for instructions: http://codepoint.raggedred.net/ . Post codes cover specific areas (essentially polygons). Post-Code Centroids show the central point of those polygons. It’s useful information which can be cross referenced with other information (see below).

• Shops are keen to get business, so often have websites or Facebook pages on which they will advertise their address to the public, including their post code. It is considered perfectly acceptable to use this information to update OSM (https://osmfoundation.org/wiki/Licensing_Working_Group/Minutes/2023-08-14#Ticket#2023081110000064_%E2%80%94_First_party_websites_as_sources). So if you see a shop, look up its website/facebook/other social media pages and it may well give this information. Use this to update the shop.

• Almost the same as the above point, but don’t forget that often there are businesses run from home. If you use Google or another search engine to search for a specific address. You may find there’s a business that’s run there, even if it doesn’t have a shop front. E.g. plumber or dog groomer. If that business has a website, Facebook or other social media page, it may include a post-code.

• Look at existing data on OSM and use common sense. It sounds obvious, but if there are 3 terraces of houses and there’s a shop at the end of the first terrace, and a house in the third terrace, both of which have an identical value for their “addr:postcode” tag, then it’s almost a guarantee that all the houses and shops in all three terraces will share that post-code.

• Do you have friends who live in that area? Ask them what their post-code is.

• Last of all: You can even ask the people who live there. If you’re walking down a street, it may be possible to ask those already outside their homes what their post-code is. They usually will know this. Try not to act suspicious. Be friendly, smile(!), and explain openly why you’re asking (E.g. “I’m a volunteer updating a free, publicly available map service. May I please ask you, what is the post-code of your house?”). If they seem suspicious of you, don’t pressure them. It’s understandable that people don’t trust everyone. Be polite and thank them for their time.

There are lots of other good methods and sources which I’ve probably forgotten. I’ll try to update this page if I think of them. But please don’t copy from OS or Royal Mail. Also don’t copy data directly from Google or other search results, or from any other site which licences data from RM or OS.

IpswichEdits