[OSM-dev] Clustering of points

Bjoern Hassler bjohas+mw at gmail.com
Tue May 16 22:19:07 UTC 2017


Hi Darafei,

That's excellent, many thanks. I'll explore this.

All the best wishes,
Bjoern

On Tue, 16 May 2017 at 21:32, Darafei "Komяpa" Praliaskouski <me at komzpa.net>
wrote:

> Set up database and import your area of interest:
> https://switch2osm.org/loading-osm-data/
>
> You'll also need a software for visualization (QGIS, install
> QuickMapServices plugin).
>
> Let's say you want to get the clusters of buildings closer than 60 in
> Minsk (I just happen to have it at hand).
>
> You connect to database and issue a query like this:
>
> create table buildings_clustered as (
>     select
>         ST_ConvexHull(
>             unnest(
>                 ST_ClusterWithin(
>                     way,
>                     60
>                 )
>             )
>         )       as geom,
>         'block' as class
>     from planet_osm_polygon
>     where
>         building is not null and
>         ST_Intersects(
>             way,
>             (
>                 select way
>                 from planet_osm_polygon
>                 where place = 'city' and
>                       name = 'Минск'
>             )
>         )
> );
>
> After it finishes, you can look at result in QGIS:
>
> [image: image.png]
>
> To make writing and formatting SQL simple, I use DataGrip (
> https://www.jetbrains.com/datagrip/download/).
>
> Docs references:
> https://postgis.net/docs/manual-dev/ST_ClusterWithin.html
> https://postgis.net/docs/manual-dev/ST_ConvexHull.html
> https://postgis.net/docs/manual-dev/ST_ConcaveHull.html
> https://postgis.net/docs/manual-dev/ST_Intersects.html
>
> Hope these are enough building blocks for your task.
>
>
> вт, 16 мая 2017 г. в 21:00, Bjoern Hassler <bjohas+mw at gmail.com>:
>
>> Hi Darafei,
>>
>> Thanks for the quick response. I'm not hugely familiar with the tools,
>> but quite possibly that is all that's needed.
>>
>> Do you have some code, or link to a recipe or a good page to get started?
>>
>> Thanks!
>> Bjoern
>>
>>
>> On 16 May 2017 18:34, "Darafei "Komяpa" Praliaskouski" <me at komzpa.net>
>> wrote:
>>
>> Is there anything in this that's not covered by importing OSM data using
>> osm2pgsql and then using a combination of PostGIS's ST_ClusterWithin and
>> ST_ConvexHull?
>>
>> On аў, 16 мая 2017, 20.28 Bjoern Hassler <bjohas+mw at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> I'm interested in clustering of OSM points, as sometimes seen on maps,
>>> as well as finding convex hulls. Basically the idea is to assist mappers in
>>> locating villages in remote areas in sub-saharan Africa.
>>>
>>> Would anybody be interested in discussing this, and work out what the
>>> options are?
>>>
>>> We're working with health workers in Zambia, and might be able to write
>>> a publication on this, in case it's motivation for somebody to participate.
>>>
>>> All the best wishes,
>>> Bjoern
>>> _______________________________________________
>>> dev mailing list
>>> dev at openstreetmap.org
>>> https://lists.openstreetmap.org/listinfo/dev
>>>
>>
>>
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