[OSM-dev] OSM data import using osm2pgsql... what's next.

[Loic Duros]

Hello Christian:

Thank you for answering my question. This is definitely extremely helpful.


On Wed, Jul 30, 2014 at 1:29 PM, Christian Quest <cquest at openstreetmap.fr>
wrote:

>
> The PostGIS in Action book has an interesting example of query:
>> "Suppose the task at hand is to find the total length of all interstate
>> highways in the state of Utah. We search for two tables: one with the
>> polygons for all the states and one with all interstate highways in the
>> United States, represented as linestrings. Next we extract the polygon that
>> represents Utah from the states table and perform an SQL join with the
>> highways table using
>> the geometric intersects function as the join operator and geometric
>> intersection as
>> our output function. The output of that query would be those portions of
>> all highways
>> within the state of Utah."
>>
>> Is such a query doable with the postgis database generated by osm2pgsql?
>>
>
> Yes
>
> It is not designed for that, but I regularly use it that way.
> Be aware that osm2pgsql does not keep all OSM data and tags. This is
> controlled by the style file (or style LUA script) during import.
> Be aware also of the map projection. By default osm2pgsql will reproject
> OSM lat/lon into web mercator coordinates. Doing real distance based
> queries will require reprojection...
>
>

When you say that osm2pgsql will reproject OSM lat/lon into web mercator,
and that real distance calculation will require reprojection, do you
actually mean re-importing the data in a different manner in the database,
or is there a way to do the conversion on the fly with a query or using
custom client code?



Again, thank you for all your help!
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