[OSM-dev] Slippy Map Elevation Overlay

Graham Jones (Physics) grahamjones at physics.org
Wed Apr 29 19:41:10 BST 2009

Ah yes - I was lazy and didn't render all zoom levels - I only did a couple
to see what it looked like.  The blockiness goes away if you render the
The problem I had though was that some of the tiles appear half transparent
like I intended, and sometimes they look like pretty solid colour that
obscures other map features.  It's almost as though OpenLayers is displaying
the lower zoom level tiles as well as the top one.   I've never looked at
WorldWind - I might have a quick look this evening.


2009/4/29 MilesTogoe <miles.togoe at gmail.com>

> Graham Jones (Physics) wrote:
>> I sometimes think that the main slippy map has a bit too much plain white,
>> especially in undeveloped places where there are not many roads such as the
>> Pennines or North Yorkshire Moors in Northern England - I keep wondering if
>> this is an un-mapped area, or if there is nothing there....
>> The cycle map is very good with shaded elevation contours, but the main
>> osmarender and mapnik maps do not include this.
>> I would like this sort of shading to be available for the main map too,
>> but I am not convinced that rendering it into the tiles is good, because
>> sometimes those extra colours or contour lines are a distraction, so it
>> would be nice for the user to be able to switch them off.
>> I wondered if there is any reason why we could not create an overlay of
>> elevation information (contours and or shading) that could sit on top of the
>> main map as a user selectable leayer?
>> I have had a quick go at http://maps.webhop.net/srtm.html.  It sort of
>> works - the high ground stands out, and you can see the shape of the ground,
>> and you can switch the overlay off and on.  It does not work that well as an
>> overlay though because it is not really transparent enough.  I find that
>> sometimes the transparency works quite well and you can see the map
>> underneath, and others it is practically opaque.
> pretty nice, though when zoomed in, it gets blocky - maybe this is actually
> how the parcel boundaries are, maybe you where just trying to get stuff
> prototyped.    I keep thinking it would be nice to integrate OSM data with
> free satellite data like java based WorldWind NASA data as the background -
> haven't really researched this yet.

Dr. Graham Jones
Hartlepool, UK
email: grahamjones139 at gmail.com
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