[Talk-us] Whole world files

[Richard Weait]

On Fri, May 28, 2010 at 12:42 PM, Fred Hillhouse
<fmhillhouse at comcast.net> wrote:
>
>> > Greetings,
>> >
>> > I just joined this list. I looking forward to learning more
>> about what
>> > is going on and providing help somewhere in the future.
>> >
>> > In the meantime, I found files for the whole world and also
>> for some
>> > limited areas. What I was looking for was files
>> specifically for the
>> > USA. I was thinking along the lines of grid squares, like
>> FN43 (maidenhead).
>> >
>> > Does anyone know if these subsets might be available?
>> >
>> > As a follow up, if I downloaded a world file and unzipped it, would
>> > the directories and files be in the "slippy" format?
>> >
>> > Downloading the entire world is pretty much pointless for
>> me since I
>> > spend my time in the 6 states of New England (ME, NH, VT,
>> MA, RI, CT).
>> >
>> > Thank you for considering my questions!
>>
>> Hi Fred, and welcome.
>>
>> There are subsets that we call 'extracts' of the planet file
>> available for smaller areas of interest.  Some tips and
>> background here.
>> http://weait.com/content/openstreetmap-extracts
>> http://weait.com/content/combine-openstreetmap-extracts
>>
>> When you download the planet, or extracts, they are usually
>> in OSM's xml format.  So, no, not images for a slippy map.
>> Other formats are available, like pre-built files for Garmin
>> GPS receivers, and others.
>>
>> So, welcome again and enjoy.
>>
>
> Hi Richard,
>
> After reading through the different pages available there, I am still
> clueless of a direction to go..
>
> I will tell you a bit about the application I am using and maybe another
> clue from you may help.
>
> The application (APRSIS32) that I am uses the OSM tiles for display. As I
> move the map about, tiles are grabbed it they are not local. I would guess
> you are very familiar with these 256x256 tiles.
>
> I have been retrieving tiles using two methods; move the map manually and
> let the application grab them or moving the map via a GPS simulator. The
> first method is tedious and I have to move to each zoom level to get
> appropriate tiles. The second, I create a file of the path to follow. This
> is not too bad since it can run unattended. I do have to run for each zoom
> level.
>
> What would you suggest?
>
> Thanks!
> Fred

Dear Fred,

That program you are using, is that related to the APRS amateur radio
stuff?  Sounds like great fun.

The OSM planet file, and the OSM extracts are in OSM XML format.  They
are not the slippy map tiles.  I'm not aware of anybody who prepares
slippy map tile extracts for areas like the US North East.

I would caution you about using an automated method of retrieving
tiles from the OSM server.  First, there is a potential problem that
you would download a row before an OSM update and the next row after
the update.  That might give you adjacent tiles that don't line up.
That's a minor consideration even though OSM updates happen many times
per second.

The largest concern that I have is that automated downloads of large
numbers of OSM tiles makes a large and noticeable load on the OSM
servers.  There are times that the server administrators will notice
this unusual load from a single user, and that their load is adversely
affecting other OSM users.  They can and will block users who
adversely affect other users.

The tile usage policy is here, as well as some suggestions for
alternatives to scraping tiles from the server.
http://wiki.openstreetmap.org/wiki/Tile_usage_policy

Those alternatives include 1) building your own tile server, or 2)
using a commercial provider of OSM tiles.

I'll have a quick look here and see how much time and space it would
take me to create those tiles for you.  I'll let you know shortly.