I don't know exactly what sort of space partitioning algorithm OSM uses, and I wonder if the OSM supports what I want.

Basically, if you want to render france, you render it at a certain zoom level, and you obviously don't query small street data. At this point, does it make sense that if I don't want to zoom and display areas and details which are under 50km, the entire planet data would be much smaller than the 40GB file download.

Is there such available download, if not, is it supported in the API ?

asked 26 May '14, 18:56

jokoon's gravatar image

jokoon
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accept rate: 0%

quite the same question as different-level-of-detail-at-different-zoom-level-api, isn't it?

(27 May '14, 17:22) aseerel4c26 ♦

No, OpenStreetMap doesn't have such a kind of download. OSM always works at the highest possible resolution.

To some extent it is possible to download a selection of data - e.g. just the boundary of France - using tools like the Overpass API, but again the boundary will be at maximum resolution.

If you want to draw a map for low zoom levels, maybe you shouldn't use OpenStreetMap at all - head over to http://www.naturalearthdata/ and check out what they have.

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answered 26 May '14, 19:04

Frederik%20Ramm's gravatar image

Frederik Ramm ♦
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accept rate: 24%

Frederik is right. Moreover, natural earth data has shorelines and boundaries simplified for lower zoom levels using some sophisticated node elimination algorithms. I played with the 10m and the 110m datasets and coastlines are heavily reduced - meaning performance goes up.

I suspect that some aggregation algorithms are implemented in mapnik, since features are simplified at lower zoom levels.

(26 May '14, 19:57) MatthiasN

so how are the lowest zoom PNG generated (meaning browsing at the scale of continents) ? if that's the case doesn't that mean generating low zoom is expensive ?

(26 May '14, 20:30) jokoon
2

The fact that the data is distributed as a big blob, doesn't mean that whoever renders a map from it can't preprocess parts of it or combine it with other lower resolution datasets. Also since the low zoom tiles are catched it is not really a problem if is more expensive to generate them.

Read https://github.com/gravitystorm/openstreetmap-carto for the map style used by openstreetmap and follow some of the links for the data sources mentioned there.

(26 May '14, 22:12) cartinus
1

@jokoon yes, low zoom tiles are expensive (most so in the "middle" zoom range)

(27 May '14, 07:57) SimonPoole ♦

any planet dataset file in some "minimal" or "lite" version or with a low zoom level ?

(28 May '14, 00:12) jokoon
1

@jokoon No - see SimonPoole's answer ("... no ... you will need to download an extract for the area you are interested in and filter out what you don't want.")

(28 May '14, 00:19) SomeoneElse ♦
showing 5 of 6 show 1 more comments

The simple answer: no.

The more complicated one: to acheive what you want you will need to download an extract for the area you are interested in and filter out what you don't want.

Extracts for example http://download.geofabrik.de/

Filter for example: http://wiki.openstreetmap.org/wiki/Osmfilter

But there are many ways to skin a cat.

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answered 26 May '14, 19:05

SimonPoole's gravatar image

SimonPoole ♦
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accept rate: 19%

edited 26 May '14, 19:07

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question asked: 26 May '14, 18:56

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