[OpenLayers-Users] technical questions about OpenLayers implementation

[Christopher Schmidt]

On Sat, Apr 14, 2007 at 06:45:56PM +0200, Pedrazzi Gelsomini wrote:
> Hello,
> 
> I developed  a web application with an interactive map using OpenLayers.
> At the beginning I chose OpenLayers and not ka-Map beacause throught
> OpenLayers I was able to overlap and integrate different layers, like:
> - 2 WMS layers (originated by MapServer based on an shape files archive on
> my server)
> - 1 WFS layer (originated by MapServer that queries my database getting a
> set of points localized by GPS)
> - 1 layer coming form Google that allows me to get simply satellite maps of
> the planet.
> At the end I chose OpenLayers above all beacause it allows me to use also
> the Google Maps.
> Now I would have two important questions:
> 1) I know that the Google Maps License permits to get the maps only using
> the API. Someone can explain me how OpenLayers is able to get the Google
> Maps without using the API? Are there some license problem?

OpenLayers uses the Google Maps API. You still have to include the
Google Maps API script in your page -- OpenLayers essentially provides a
wrapper around it.

> 2) OpenLayers does not have a cache tiles system like ka-Map. How can the
> interaction (zoom and panning) be so good also without this system?

Depends on what you mean by 'so good'  :)

http://openlayers.org/dev/examples/freemap.html is slow. Lots of data,
rendering antialiased, takes time.

http://openlayers.org/dev/examples/lite.html is pretty quick, but not
instant. Low resolution data, intelligent styling decisions for ease of
rendering.

http://tilecache.org/demo.html is much faster. It runs under TileCache,
which is basically the server-side component of ka-Map rewritten in
Python.

Regards,
-- 
Christopher Schmidt
MetaCarta