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The other day I was driving through an intersection, noted some feature of it (a "No U Turns" sign in my direction, or number of lanes), and made a note to later add it to the map.

However, I wonder: is it helpful to map only one direction of an intersection? Won't this cause other mappers to look at the data, see one direction has been mapped, and assume all four directions have been surveyed?

What's the best practice for such "drive-by" mapping?

Put differently, I suppose I'm asking whether mappers can distinguish between data being absent because the feature is unsurveyed, versus being absent because the feature has been surveyed and the locality's defaults (e.g., "U turns are permitted by default") apply.

asked 14 May '17, 13:21

dsh4's gravatar image

accept rate: 4%

No map is perfect and I view the process of improving OSM as incremental. If you can add or correct details you have improved the map. That is true even if you've only added details apparent when traveling in one direction.

Some day I or another mapper may be driving the other way through that intersection and notice the mapping is wrong or incomplete and fix/add more details. In the meantime, you've improved the experience of those traveling the same direction as you as their routing app will know that they can't make a U-turn at that point going that way.

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answered 14 May '17, 14:40

n76's gravatar image

accept rate: 17%


If you know that some feature is missing but can't map it because it needs to be surveyed, add a note or a fixme to attracct other mapper's attention. But avoid issues that are automatically pointed out by QA tools or obvious from the satellite imagery.

(15 May '17, 11:32) Vincent de P... ♦

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question asked: 14 May '17, 13:21

question was seen: 2,027 times

last updated: 15 May '17, 11:32

NOTICE: is no longer in use from 1st March 2024. Please use the OpenStreetMap Community Forum