[OSM-dev] Trial clickable POI layer

Martijn van Oosterhout kleptog at gmail.com
Fri Sep 21 18:43:14 BST 2007

On 9/21/07, David Earl <david at frankieandshadow.com> wrote:
> I think it is going to need separate "tiles" at each zoom level so the
> amount of data can be throttled (I assume this isn't going to the
> database for each overlay, but pre-generating them like the image tiles
> do, yes? If not, I think they should be - essentially they are companion
> data to the image tiles so can sit alongside the image tiles).

No, these arn't tiles. This is just a DB serving data asked for.
Basically depending on where you are the client requests a bbox and
the server gives it a list of POIs. I don't really want to go down the
route of making tiles of them, the data (currently only 60,000 POIs)
just isn't enough to justify it.

So when you load the map there is only *one* request to the server, no
matter what zoom-level you're on. And you need to pan quite a bit to
trigger a new request.

> I suggest the "horizontal" text (names of POIs, place names etc) is also
> in these "tiles" (maybe a separate layer, I don't know what layers can
> hold, but if it is html, it can be both simultaneously).

You mean display the names always? Without clicking on anything?

> I would also put _all_ the POIs (determined as useful for that zoom
> level) on one layer (two layers with text if necessary), but give them
> an HTML class; then have a control dialogue somewhere which allows the
> user to turn on and off the icons/text for particular classes of POI.

I like the class idea. I have prectically no experience with
stylesheets, but the possiblities are there. Do you have some idea of
what kind of things we want to be selectable?

Have a nice day,
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/

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