[OpenLayers-Users] Large Vector Layer

[Gregor Mosheh]

Scott Davis wrote:
> I have a datalayer that has ~10,000 bus stops (points).

WFS is basically like GeoRSS in that it communicates XML about vector 
data, and that the browser must decipher the XML. Differrence 1 is that 
it can describe more than a point; difference 2 is that it's even more 
verbose and therefore XML parsing is even slower.

So if you're in a circumstance (say, zoomed out to the city-wide view) 
where you'll want to see 1,000 points or even 500, you probably won't 
enjoy the effect.

This has been a thorn in my side for a few years, wanting to use WFS but 
finding it impractical for any significant scales of use.


At FRUGOS a few months back where I met you, I presented my solution 
when I had the same issue in Google Maps. My solution was to use a WMS 
layer, then have a click handler that would do the real magic:

1. Grab the data for the point, e.g. GetFeatureInfo to GeoServer
2. Draw a popup box anchored at the appropriate location on the map, 
containing the data.

The visual effect is that they clicked and got a popup, but you get to 
bypass the overhead involved in true Features. I know that OL can do all 
of the above. For (1) there's a Freemap of the CIA Factbook 
demonstrating click-to-query code. Part (2) should be very easy once you 
have the data and have generated the HTML.

-- 
Gregor Mosheh / Greg Allensworth
System Administrator, HostGIS cartographic development & hosting services
http://www.HostGIS.com/

"Remember that no one cares if you can back up,
  only if you can restore." - AMANDA