[OSM-dev] {To Brett} Re: OSM Data Question from FireGirl

Andy Robinson (blackadder) blackadderajr at googlemail.com
Wed Feb 13 10:40:22 GMT 2008


Fire Girl wrote:
>Sent: 13 February 2008 5:03 AM
>To: dev at openstreetmap.org
>Subject: Re: [OSM-dev] {To Brett} Re: OSM Data Question from FireGirl
>
>
>	Firstly you need to figure out what you want to do with the data :-)
>	That will help limit your options. You'll need to determine things
>like:
>	1. How many different areas do you need?
>	2. How large are the areas that you need?
>	3. How up-to-date does the data need to be?
>
>	If you're pulling out many different areas at regular intervals then
>	something like osmosis will give you a lot of flexibility. If you
>need
>	a specific area that isn't *too* large, osmxapi will be the
simplest.
>	If up-to-date data isn't critical then a pre-generated extract may
be
>	more appropriate.
>
>	In general, large amounts of data are best served by osmosis. With
>	osmosis you can slice and dice to your hearts content without
>consuming
>	server resources (other than the initial planet download). Very
small
>	areas may be served by the standard osm api but try to limit your
>usage
>	of this. Somewhere in between lies osmxapi which will handle larger
>	areas than the main API, but probably not ideal for downloading
whole
>	countries.
>
>	The main API will provide the most up-to-date data, osmxapi will be
>	within 10 minutes, and osmosis just works with whatever files (ie.
>	planet file) and changesets (ie. daily/hourly/minute) you choose to
>	download but can also be within 10 minutes with a bit of effort.
>
>	If you're just trying to get used to OSM and don't know what you
need
>	yet, I'd suggest downloading one of the extracts suggested by
Milenko
>	(http://planet.king-nerd.com/usa/) and playing with it. When you get
>	something working using that data then you can figure out how to get
>	your updates to that data.
>
>
>
>
>
>
>Ah thank you Brett... I think this is leading me down the right path. :)
>Basically, yes, I am looking for a Pre-Generated extract and just plan to
>use the OSM data for in-house rendering (don't need to serve it up). So
>given that fact, it sounds like osmxapi - is the way to go to get to
>specific tailored OSM data files?  I am a Windows girl, but can setup Linux
>with some effort ... but maybe you know a way to do this in Windows.  I've
>got a pretty souped up box and that would be ideal for me.
>
>One thing I noticed is these OSM files, ..... even State files are very
>huge.  They sit in a compressed BZ2 format like at 50MB for a state... but
>once you fluff it up, it grows to over 1GB for just one single State.
>........ Can the data within these compressed files be extracted for what
>is needed without fully un-compressing it.... or *must* you un-compress it.
>I guess that is a stupid question perhaps, but just checking.
>
>finally... what is on my mind is, let's say I need to get to just a very
>small geographic region, a Neighborhood within a City within a State for
>example.  To extract the OSM file for a City, I need BBOX coordinates,
>correct?  If that is the case, what is my best bet for getting to the BBOX
>(I hope I am using the correct nomenclature), to finagle the
>SOME_CITY_DATA.OSM file (for instance) from a SOME_STATE_DATA.OSM file?
>Using osmxapi first against the STATE OSM file that contains the CITY i am
>interested in? :)

If it's a very small area you need then just downloading that area from the
main API or via osmxapi will give you what you need. The limit on the main
API is a 0.25degree area. Queries that are bigger should be addressed to
osmxapi which does not have that restriction. For the main API you can also
use JOSM to download the area of data directly into the editor.

To get bbox values I normally use http://www.informationfreeway.org because
that has the lat and lon of the pointer displayed in the bottom right hand
corner.

Cheers

Andy


>
>Am I on the right track in my thinking here?
>
>**** Summary *****
>
>LOGIC: >> STATE OSM FILE (1GB) > COULD POTENTIALLY EXTRACT INTO 100'S OF
>CITY OSM FILES USING OSMXAPI
>
>QUESTION: IS OSMXAPI THE FASTEST WAY TO JUST GET FIXED DATA FOR IN-HOSUE
>RENDERING, NON-SERVER USE?
>
>ALSO: IS THERE A WINDOWS PATH TO GETTING TO THIS LIMITED DATA?
>
>AND FINALLY: HOW TO NAVIGATE RELIABLE BBOX COORDINATES, I presume to feed
>into OSMXAPI to get to smaller Sub-Set data files for Cities or smaller
>areas :)
>
>Have a very nice evening.
>Best wishes, FireGirl.
>
>--
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