Editing Standards and Conventions

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For more general recommendations and tagging recommendations, see Good practice.

The following are some Standards and Conventions for editing the maps.

Tagging

Roads

A physical road, street, footpath, etc. is initially drawn as a series of nodes grouped together to form a way. The way should then be tagged with a highway=* tag and a name.

Many ways appear the same in most of the OSM editors, however, when rendered they will be displayed in different colours and widths based on the tag values entered.

Street Names and naming conventions

Don't use abbreviations

Don't describe things using name tag

Unnamed objects

Objects (usually streets) which have no name:

  • without name=* or it's variants
  • additionally could be tagged noname=yes

See also


One way streets

If traffic can only travel down a road oneway then it is important to draw the way in the direction of travel and then add a oneway=yes.

Divided highways

A divided highway (also separated highway) is any highway where traffic flows are physically separated by a barrier (e.g., grass, concrete, steel), which prevents movements between said flows. While divided highways typically consist of two opposing traffic flows, such as with dual carriageways, they can also consist of three or more divided sections having a combination of same-direction and opposing flows, such as highways with "local" and "express" lanes (whereby entries to and exits from the highway are possible only from the former).

Divided highways should be drawn as separate ways. The ways will typically be oneway=yes, and should be tagged as such where appropriate. Ways connecting the divided ways should be drawn at locations where movements between the divided ways are possible, that is, where the physical separation is interrupted (e.g. [1]; as always, add access tags for legal limitations). Where the divided ways are parallel (often, but not always) their nodes should be positioned so that they are adjacent to each other. This creates a more pleasing aesthetic effect in renderers, especially on curves. It also preserves the information on their mutual separation distance along their whole length.

As with any ways, the spacing between is governed by the need to accurately represent curves (see below):

Wrong.
Right. Nodes aligned in pairs.

JOSM tools

JOSM contains several tools that will save your time and ease your pain during editing process

Roundabouts

See Roundabouts

Junctions

See also Node#Nodes_on_Ways

All road junctions should be drawn as a node which connects the ways (both or several ways share the same(!) node).

It is incorrect to use two nodes are just on the same (or nearly the same) position but actually are not the same. While this might look right, it will not define a valid routable connection from one road to the other.

If your editor's map style does not make shared nodes discernable, then a usual trick is to just move the node in question a bit and watch which ways move too. Please be sure to "undo" (with your editor's "undo" function, not by moving back(!)) this test move.

Some quality assurance tools help to discover such potential connection problems (way end closely to another way but not connected).

Bridges

Bridge ways are tagged bridge=yes and layer=1

A bridge is drawn as a separate way. This is one of many situations where a road is no longer represented as a single way, but as several ways arranged end-to-end, each with different tagging. The editors provide an easy way to split a way at a given node, for this purpose.

The highway and name tag should be applied throughout. The short way representing the bridge should additionally be tagged with bridge=yes and layer=x, where x is one more than the layer tag of the road underneath (or 1 if there is no layer tag on the road underneath).

Often the bridge will not connect directly to a junction. In which case you should add a piece of road connecting the two (see image):

Bridge near junction

See Key:bridge for details.

Tagging Areas

Areas are closed ways

On some occasions the feature you wish to tag is not represented by a line (as is the case of a road, river, rail line etc), but by an area. For instance a wooded area, a park, or a lake are all Map features which are areas. Create a new closed way which represents the outline of the required area. Annotate this way with the required tagging from the map features page, such as natural=water (for a lake), landuse=forest (for a forest), or leisure=park (for a park), etc.

Highways as Areas

Most ways are assumed to be areas if they are closed (i.e.--if the way connects back to itself). However, there are some exceptions to this, such as highways, which are generally assumed to be ways. If the highway is meant to be an area (for example, a pedestrian square), then an area=yes tag should also be added, to imply that this feature is not just representing the way that forms the border, but the area within it, too.

Areas and Ways Sharing Nodes

There is not clear consensus yet on how to draw areas adjacent to ways. They may be drawn either by leaving a small gap between the area and the way or by connecting them so that the area shares nodes with the way. That being said, when the way is a highway, it usually is most accurate to include a gap, so that the area ends by the side of the road and does not share nodes with the road's way. This is because highway ways usually are traced along the centerline of the road, and it is unlikely that the area being tagged actually extends to the center of the road.

Accuracy

See main article: Accuracy

Accuracy is important during mapping. Beware of systematic errors of aerial imagery (see for example Bing#Precision). Remember, that when tracing roads — particularly winding, rural ones — you should add enough points to make each curve look like a curve. Of course, this is entirely subjective, as curves made entirely of lines will only ever approximate a "true" curve (which has an infinite number of nodes), and will always look like a series of lines when zoomed in past a certain point no matter how many nodes there are.

To generalize, though, sharp curves (those having a small radius) require many, closely-spaced nodes, while broad, long-radius curves can consist of fewer nodes having more distance between them. Without a hard-and-fast rule, it is best said to simply use good judgement and strive to seek a balance.

Small example using GPS traces

Below there is an example of a very roughly-traced rural 2-kilometer road. It's rather crude, particularly on the sharp curves. We would normally expect mappers to represent this kind of road with more nodes than that.

How it shouldn't be done

This is the same 2-kilometer road - but this will look much better on the map, and gives the map user a better sense of the curves of the road. You can see the road on the map. You can see, that ... other mapping services] have a similar degree of accuracy.

How to do it

Note: Keep in mind that the road in the diagram below is about 2 km long. For very short roads you do not need to add that many nodes. If a road is perfectly straight then a node at either end is always sufficient, regardless of how long it is.

It's easy enough to "fix" these things i.e. enhance the detail of the road. Normally you should just add more nodes to the existing way. If you choose to delete and redraw a whole road, check that the nodes don't themselves have tags e.g. a highway=crossing node. Potlatch and JOSM] will highlight tagged nodes.

Date and time

Simple definition

Dates should be in ISO 8601 format, i.e. YYYY-MM-DD.

Precise tagging

Miscellaneous

  • Intersections and interchanges - These are most likely to be always improved by someone else, no matter how much detail you put in
    The initial level of detail should include correct connections from/to each road and link road and the existence of any bridges and underpasses; remember to set oneway tags where applicable.
    For intersections any pedestrian crossings are valuable information; add a node in the way they cross at their location
    After that there's still lots of detail that can be added (as with all roads: number of lanes, speed limits, lit=yes/no
  • Accuracy. How do you judge and or indicate the accuracy? How accurate is good enough? Is a rough approximation better than nothing (i.e. inaccurate roads get refined the way wikipedia articles do).
    A GPS trace is almost always more accurate than other sources available to us. Still several, even tens of traces can be used to improve the accuracy. Do note though:
    • Sometimes and in some environments the GPS trace can wander off to some direction (often 15-30 meters but even 90 meters); compare the trace with your memory, photos and notes to see if straight roads appear as a reasonably straight set of trace points.
    • If it's a new road (nothing previously entered in the area) and there aren't any aerial images available, draw it in anyway
    • If there are already other roads around and your trace seems bad, try to deduce the "real" form from the trace by not crossing roads that don't intersect with the road you traced.
    How accurate is good enough varies with each user:
    For most uses it's accurate enough when it's not misleading: say when a cycleway drawn on the map
    • shows all correct bends and intersections
    • and no nonexistent ones
    • and is on the right side of the nearby road / stream / railway
    • and is roughly the correct distance away from those features (some editors have support for measuring distances)
    Some may later want to draw fences, hedges and walls around the houses (where they exist); they will have mapped their locations to within a few meters by repeated traces and considerable amount of deducing and aligning things in lines
    Not only inaccurate roads, but those lacking secondary information, are refined later anyway. When contemplating on whether to approximate some road, try to consider if a user would find any value in the approximated form - is it likely to be within, say, 50 meters from the real location at all times (in otherwise unmapped territory)? If you approximate, do add a source=approximation or similar tag to the way.
  • Is it constructive/helpful to mark a road that you know is roughly in the right place but don't have any supporting GPS data?
    This depends again on what else is there:
    • If an urban road is missing in a rectangular grid and you confirmed its existence and it was, say, roughly halfway between the parallel roads: the position is likely to be almost as good as the position of those parallel streets when you draw it in.
    • If the missing road ventures into the unmapped territory winding along the way, it's likely better to draw just a stub for the starting point and add a FIXME=continue on the last node. If one were to draw the full way freehand, it would very likely be too short/stretched/skewed - unless there are good aerial images available.
  • Landmarks, footpaths, etc.?
  • How do you indicate that one road passes over or under another? - See the description for bridges above, and Key:bridge.
  • If a road is made up of several/many ways, all ways should carry the name and/or ref tags.

Topology

  • Is correct topology more or less important than accurate location?
    • In the end both are equally important and not even mutually exclusive, but since with our tools the topology can be surveyed more accurately than the location, it should be always kept correct, even if that leads to some nodes being some meters more off than otherwise.
  • If a road is a dual carriageway it should be shown as two lines
  • If a road has a small traffic island (eg at the approach to a large roundabout) should this be represented as a triangle or not? How big should it be before it should be drawn?



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