Tiles vs. WMS, problems to understand WMS

wyo · 2010-08-07T09:27:22.000Z

Neider http://wiki.openstreetmap.org/wiki/WMS nor http://en.wikipedia.org/wiki/Web_Map_Service are very informative about what WMS really is. As much as I understand WMS produces images yet I don’t understand what’s the difference or advantages to tiles. Could anybody enlighten me or better update the Wiki and/or Wikipedia so this is understandable by anybody?

Wyo

amm · 2010-08-07T09:59:30.000Z

Not directly meant as an introduction, but http://wiki.openstreetmap.org/wiki/Mod_mapnik_wms#What_is_WMS.3F has a short comparison of the differences between WMS and tiles. Basically WMS is supposed to be more flexible, but potentially needs a lot more resources, so doesn’t scale as well to many users.

JRA · 2010-08-07T10:50:08.000Z

These pages should work well as a general introduction:
http://docs.geoserver.org/stable/en/user/services/wms/index.html

wyo · 2010-08-07T12:07:30.000Z

Yet as much as I understand WMS does provied maps in form of images (png, jpeg, etc). Are these single images for the whole requested map or specialised rendered tiles fitted together on the client?

JRA · 2010-08-07T13:12:20.000Z

Output is allways one image per request, size (in pixels) set by HEIGHT and WIDTH parameters. Client can deside to make smaller requests and combine them together on the client side. See wms and wms-untiled examples from http://dev.openlayers.org/releases/OpenLayers-2.9.1/examples/

Here is another example that should show you a map with two simple layrs on a browser
http://www2.dmsolutions.ca/cgi-bin/mswms_gmap?SERVICE=WMS&VERSION=1.1.1&REQUEST=getmap&layers=park,popplace&STYLES=&SRS=EPSG:4326&BBOX=-173.537,35.8775,-11.9603,83.8009&WIDTH=400&HEIGHT=300&FORMAT=image/png

Change layers=park,popplace to layers=park and you will see a difference. WIDTH=800&HEIGHT=600 will give you a bigger image.