Almost everything I have surveyed for OSM was collected while going to places I had to go to anyway. I do take different paths every time in order to collect more data, but I haven't yet done a “purposeful survey”.

Among many other things, I have collected partial information about the surface of some streets (ie. whether certain segments are paved or not). However, I haven’t traveled through any of these streets from end to end. I’m wondering how to tag this partial information.

I think my options are:

  1. If I know the surface of part of a street, mark the whole street as such.

    Problem: It may turn out that elsewhere on the street the surface changes, so I’d be introducing bad data. I already know of streets that change surface, and more than once.

  2. Split the way at the boundaries of my knowledge. Mark only the known segment(s) with a surface tag. Leave the rest untagged.

    Problem: It will probably turn out that the same surface continues past those boundaries, so I would be doing a lot of useless splitting and re-combining. In the very worst case, I might survey n non-​adjacent segments, split the way into 2n+1 pieces, and weeks later find that the whole street had the same surface and combine it all back together.

  3. Don’t upload anything yet. Keep the data locally, and only send it to OSM once I collect information for the entire length of a street.

    Problem: This could take a while. Maybe I’ll never get around to it. Partial information should be better than nothing.

I’m gravitating towards option #2, but I’d like long-timers to comment on whether it’s acceptable or not to split ways for this reason. What are the practical consequences of split streets? Are newbies confused by them? Is it “common” for mappers to mistakenly set tags to only one of the segments without noticing it’s split, when it’s data that applies to the whole street?

What about all the splitting and recombining, do we really care about too much or useless creation and deletion of elements? Sometimes I’m obsessive about that, and for example, when aligning ways, instead of deleting excess nodes and adding necessary ones, I try to move the nodes already there; even though I rationally know that nodes aren't a scarce resource :)

asked 29 Nov '12, 06:14

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nicolas17
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edited 29 Nov '12, 13:28

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Vclaw
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OpenStreetMap lives from partially surveyed data. The problems you describe aren't really problems but just common situations you can find everywhere. Ways have to be split for lots of different reasons as for example different maxspeed restrictions, route relations, varying names, changing access restrictions and of course also different surface tags. Splitting is a common task and should be done whenever necessary. If you later find two adjacent ways having the same tags and same relations then of course you can just combine them into a single way again, but this is not necessary.

In my opinion you can tag the whole street with the same surface if you are pretty sure that it won't change even if you haven't surveyed all parts of that street. If there are errors you or somebody else can correct them later. But if you are really unsure about the unsurveyed part of the street then better just split it and only tag the surveyed part of it.

In my own experience splitting a way looks odd to new mappers at first. Some of them think they can somehow mark specific parts of a way and apply tags to them. But they get used to it soon.

Of course it also happens that tags are added to long ways when they only apply for parts of it. This is just one single case of various mapping errors. Finding such an error isn't easy at the moment as surface tags aren't rendered on the main map but this might also change in the future.

There are also unofficial maps visualizing the surface tags as for example ITO Map.

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answered 29 Nov '12, 08:01

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scai ♦
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Bing imagery is of help here, as changes in the surface can often be seen as colour changes in the image. A uniform colour will give you confidence that the surface is consistent between the surveyed and unsurveyed parts of the street

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answered 29 Nov '12, 14:19

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srbrook
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1

This is unfortunately not possible at the image resolution available in my area. There is almost no difference between asphalt streets affected by camera noise and cobblestone.

(29 Nov '12, 20:14) nicolas17
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question asked: 29 Nov '12, 06:14

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