[OSM-newbies] Downloading only updated tiles

[Andy Allan]

On Mon, Aug 11, 2008 at 1:21 PM, Risto H. Kurppa <risto at kurppa.fi> wrote:

> So is there a way to update my local maps so that only the changed
> tiles would be downloaded? rsync that checks if the file is changed
> and then updates?

You can use the ETag HTTP header from the tiles to see if they have
been changed, so long as your application keeps track of them. See
http://en.wikipedia.org/wiki/HTTP_ETag

andy at everest:~$ curl --head http://a.tile.openstreetmap.org/9/256/170.png
HTTP/1.1 200 OK
Date: Mon, 11 Aug 2008 13:58:21 GMT
Server: Apache/2.2.4 (Ubuntu)
ETag: "da41b3eb954cb826578be4d26ccff719"
Content-Length: 24554
Cache-Control: max-age=554888
Expires: Mon, 18 Aug 2008 00:06:29 GMT
Content-Type: image/png

> I've tried asking around this in some places but so far I got around 0
> answer. So if you can help me, please do, if not, guide me to someone
> who can.

If you have more technical questions on this you can ask on our
developers mailing list.

Cheers,
Andy