[GIS] Make OpenLayers request WMS tiles only within a certain bounds

mapsopenlayers-2web-mappingwms

Is there a way to actually tell OpenLayers not to request tiles out of particular bounds?

I want the rest of map and other layers still accessible, so maxExtent on map is not an option for me. I just want to restrict one WMS layer to particular bounds. If view port is inside the bounds and user zooms in fine, OpenLayers requests new tiles! but if viewport is outside, the WMS should only fill the bounded area with tiles from that WMS layer.

Does that make sense or is that even possible?

Best Answer

You should use maxExtent option on layer level.

Related Solutions

[GIS] How to optimize a WMS request by limiting number of tiles

I think you are missing some thing here :-) This is not how WMS servers work, You are also conflating tiles and features. With tiles. If you are using tiles then the hope is that a tile will be drawn once and cached for subsequent viewings. The cache can be at the server (where the cost of drawing a tile can be shared between all users) or in the browser (where it will only benefit the user of that machine). So it doesn't really matter how many features are drawn on a tile as the next time you view it there will be no draw at all.

If your WMS (or initial tile draw) is too slow because of the number of features being drawn then the best plan is to work out why that is. Adding an index to your data will be the first thing to try, then look at the type of data store you are using (try PostGIS instead of shapefiles etc). Finally if things are still too slow look at scale dependent rendering using SLD (http://geo.ifip.tuwien.ac.at/imak/2009/stack_workshop/doc/sld_basic/scale.html) to restrict the drawing of features to the most important ones when the user is zoomed out.

[GIS] Can we request new OpenLayers WMS image for an extent without moving the map

when u check out OpenLayers.Layer.WMS structure, you can see that it inherits from OpenLayers.Layer.Grid... and when looking at api, you can notice that spiralTileLoad() may help you about what you want...

from OpenLayers doc:

spiralTileLoad: function()

Starts at the top right corner of the grid and proceeds in a spiral towards the center, adding tiles one at a time to the beginning of a queue.

Once all the grid’s tiles have been added to the queue, we go back and iterate through the queue (thus reversing the spiral order from outside-in to inside-out), calling draw() on each tile.

code:

var wms = new OpenLayers.Layer.WMS("NASA Global Mosaic",
          "http://wms.jpl.nasa.gov/wms.cgi",
          {layers: "modis,global_mosaic"});
wms.spiralTileLoad();
wms.redraw();

map.layers[i].spiralTileLoad();
map.layers[i].redraw();

i hope it helps you...

Best Answer

Related Solutions

[GIS] How to optimize a WMS request by limiting number of tiles

[GIS] Can we request new OpenLayers WMS image for an extent without moving the map

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