[OSM-dev] Clickable POIs - use marker/pushpin layer?

[Andy Allan]

On Jan 8, 2008 12:17 PM, Andy Robinson (blackadder)
<blackadderajr at googlemail.com> wrote:

> Ok, so maybe I'm off kilter here but in my mind I see the logic of having
> any point on a given map return something more than a zoom change ;-) is it
> feasible to have a transparent image map type layer that resolves to a query
> of the information?
> I hate markers so making map content directly accessible without the need
> for markers would be of real interest to me. I'm thinking of an external POI
> db or info directly from OSM. A change in the mouse pointer confirms the
> presence of a hotspot. What happens when it's activated would depend on what
> the content was.

For the case where the location of your POIs / markers / etc is known
at tile-rendering stage, i.e. not user-contributed locations:

* You could have transparent hotspots (use transparent.png for your
javascript markers) and that will make things effectively clickable
but keep the paleoStalinists happy
* You can use the map icons as markers (e.g. pub.png for the
javascript marker) and simply "block out" the space for it on the
pre-rendered tiles with something transparent. That way when the icon
layer is on it's indistinguishable from the first option, but you also
have the choice of switching off markers. I get lots of complaints
about POIs on the cycle layer obscuring junctions, for example.

Neither of these will work cleanly for overlapping icons, but you
probably want allow_overlap = true for an editor otherwise people will
get very confused. And all of it comes with the disclaimer that I
haven't actually done it yet.

There is also Lines of Interest (or something), as per the Camden
Cycle Campaign. You can see on their map a mixture where they have
their google-inspired overlay mixed with our data at
http://maps.camdencyclists.org.uk/allroutes/ - change the dropdown in
the top right to OSM Cycle and some of the overlay routes disappear
where we have the data. Although it would be nice to draw transparent
hotspotlines over the right places on the OSM tiles, so that you can
click for full details, the whole problem that they are trying to
solve with our help is that everything you add to javascript slows the
whole thing down.

Cheers,
Andy