At FOSS4G we learned a bit about how GeoMajas accomplishes this. It
doesn't answer your question about how GISCloud does it, but may be a
start on accomplishing it on your own maps using OpenLayers (or a hint
that maybe GeoMajas can do what you want).
GeoMajas sends out the layer as raster, and the layer has a click event
handler. This handler will fetch the geometry at the location and load
it into the browser, then trigger the click on the vector feature. It
isn't truly loading zillions of vectors, but the on-demand vector
loading can simulate the effect pretty convincingly.
That could easily be done using WMS GetFeatureInfo, parsing the geometry
from the response, and adding Features.
GeoMajas takes it a step further, in that the server does some
calculation to determine whether there would be too many vectors, and if
the payload is light enough it really will send vectors.
--
Greg Allensworth, Web GIS Developer
BS A+ Network+ Security+ Linux+ Server+ ZCE-PHP
GreenInfo Network - Information and Mapping in the Public Interest
564 Market Street, Suite 510 San Francisco CA 94104
PH: 415-979-0343 x302 FX: 415-979-0371 email: [email protected]
Web: www.GreenInfo.org www.MapsPortal.org
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