[HOT] next HOT tech chat

[Harry Wood]

> So, there's a few different things you could cache.
> 
> One is imagery/tiles. For tiles it's a well-solved problem, tile.osm.org
> uses a bunch of squid caches and the configuration is all at
> http://git.osm.org/chef.git/tree/HEAD:/cookbooks/tilecache
> 

It would be neat if a BRCK type device could intercept requests to tile.openstreetmap.org while an internet connection is working, and then serve the same tiles from cache if the internet is down. I'm thinking of man-in-the-middle caching on the connection device. Is that a squid-like thing to do?  That type of caching may already be a generic function of BRCK. It would mean that if you have some tool running locally, but which is designed to require an internet connection for embedded maps (hitting tile.openstreetmap.org in the standard way) it could carry on working, without re-configuring tile URLs.

...but it wouldn't have all the tiles in the region. Just those which somebody had viewed before. To have all the tiles, the temptation is to request the full pyramid as a bulk tile download. That causes problems for the server, and is strictly disallowed on the main osm tile server, but you could imagine some set-up in which aid workers are allowed to bulk-download a pyramid of tiles from a HOT tile server before they get on a plane.

Of course the smart way is to run a tile server in the field. Smart because it's more compact, and also because feeding in diffs is a reliable compact thing to do. Another "solved problem" really ...Except that the technology is somehow still far too complicated to give to a random non-technical aid worker. In fact I think even people like MapAction didn't get their heads around it. Rendering is still very much an OpenStreetMap expert skill. 

It think tiled vector data will be the key to lowering barriers here. You mentioned tiles and API data as two forms of caching, but cached *vector* data has huge potential. This is a bit more of a blue skies idea. But check out this tantalising preview from the MapBox guys: https://vine.co/v/b0DvTPnpPtw  That's the whole planet on USB key, rendering on the fly.  I think we want to get to the point where aid workers don't leave home without a copy of this. Then another challenge is allowing them to request low-bandwidth data updates when they have internet. Of course there are some pretty amazing mobile apps which use a tile vector data approach. I really love MapsWithMe, but it's closed-source and doesn't do low-bandwidth updates. Is AND the best open source one? I hope we'll see convergence on an open standard and open tools to view, and update vector tiles. What's the best way for HOT to push things in that direction?

Harry Wood






 A disadvantage is that they only cache what has been requested.



I think a remote team with sporadic internet connection. 


on the topic of HOT usb stick.... https://vine.co/v/b0DvTPnpPtw <<< The entire word rendering on the fly!