Vi:Editing Standards and Conventions

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Gán tag

You can assign "tags" ("keys" and "values") to any point (node), street (way), area (closed ways) or relation. You can find a list of suggested tags on the Map Features page. It is recommended that you take a good look at that page and familiarise yourself with the tags which are most widely accepted and recognized by most tools/renderers. Note though that any keys and values are valid and may be employed in OpenStreetMap, and the Map Features page is subject to change, with proposals being voted upon.

The Good practice page has a number of points concerning tagging.

Make sure to visit FAQ for various useful hints, like how to use multiple values for a single tag.

Đường

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.

Tên phố

In the name tag, enter the full name as it appears on the street name signs. Use mixed case with the first letter of each word capitalised (for example, Church Street, not Church street). Do not abbreviate words. There is currently no table of standard abbreviations (St. could be Street or it could be Saint) and it has been decided that this is a rendering issue. i.e. the underlying data should have the full street name. This will allow a renderer to introduce abbreviations as necessary.

Watch out for apostrophes. The same rule applies. If the street sign has an apostrophe, the OSM data should have an apostrophe. There is no obvious consistency; the London Underground station Barons Court is adjacent to Earl's Court, one with an apostrophe, one without.

Also see Bilingual street names

Đường không có tên

Sometimes a road does not have a name (in the real world) That's fairly rare, but it sometimes happens. In this case, enter the highway tag, but not the name tag.

Often a road has a name, but you don't know what it is. This might be because you didn't write it down while you were out surveying. Maybe you used a camera but the picture came out blurry. Or maybe you are sketching over Yahoo! Imagery. These kinds of roads should be drawn in as ways tagged with highway=road as per the guidelines on Yahoo! Aerial Imagery#How to sketch? ... however not everyone follows this, and "sketched" roads are often left untagged or given some other highway tag by a reasonable guess.

Đường một chiều

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 one way, 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. Where the divided ways are parallel, which is oftentimes — but not always — the case, their nodes should be positioned so that they are adjacent to each other, which 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.

Wrong Right. Nodes aligned in pairs.

Bùng binh/Nút giao hình xuyến

Kiểu đối tượng này được thảo luận chi tiết hơn tại trang này.

Junctions

All road junctions should be drawn as a node with connecting paths. It is incorrect to add a node that appears to be on a path but is actually not connected. While this might look right, it will not define a valid path from one road to the other.

An incorrectly drawn road junction
A simple road junction

Cầu

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 to throughout. The short way representing the bridge should additionally be tagged with bridge=yes and layer=1.

Bridge-Junction-Connection.png


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).


See Key:bridge for details.

Tagging Areas

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.

Độ chính xác

Accuracy is important. The GPS system provides fixes that can be accurate to 1-10m which is more than good enough for this project. Do bear in mind, however, that a road can be several metres wide and a GPS fix could have been made anywhere in the road or even on the pavement. For many purposes accuracy to a few metres is plenty good enough. What is equally important however is topological accuracy. Do two roads intersect at the same point (a crossroads) or is the intersection offset? This detail may only be a matter of a few metres, but can be the difference between driving instructions that might say at the crossroads go straight ahead or at the junction turn left and then after 10 metres, turn right.

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. Any "rule of thumb" as to node spacing and quantity would be arbitrary and capricious. 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: on one hand, remember that you are drawing a map, not just a routing diagram; on the other hand, don't try to seek perfection by adding more and more nodes past the point of diminishing returns, keeping in mind that each additional node requires that more data be stored and transferred.

Note: Keep in mind that the road in the diagram below is about 20km long. For very short roads you do not need to add that many nodes.

How not to do it

Tracing curves badly.png

The above is an example of a very roughly-traced rural 20-kilometer road. Drawing roads like this isn't helpful. When someone comes along to do it properly, he will have to work hard to refine this way by adding lots of points into it and adjust them. Nevertheless it is not recommended to delete existing items without verifying every single node if it bears some tags.

How to do it

Tracing curves accurately.png

This is the same 20-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.

Thời gian

Dates should be in ISO 8601 format, i.e. YYYY-MM-DD. Where a numeric day of week is necessary, Monday=1, Sunday=0 or 7.


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 it's 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'd 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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