Andrew Hallam at Digital Earth Weblog writes his third installment in a detailed series on Google Earth. This time he posts on getting WMS servers to show up in Google Earth, and homes in on those places where both Google Earth and WMS protocols have room for improvement.
Some notes on his notes, then:
1. Finding a WMS: One place to look is Mapdex (no surprises there). Do a search for “WMS” in Service and you’ll get 394 services from 109 servers. That’s a good start for experimenting.
2. WMS Reflector Script: I like the “reflector script” (great name) that Andrew uses, as it is quite versatile and robust, certainly more so than the one I used when experimenting on Canada, in this post.
He notes of the script that he uses, however, that “the big limitation with this approach is that the user has no control over what gets displayed. They cannot turn the individual WMS layers on or off.” He proceeds to try to work around this limitation by constructing a KML document that contains multiple network links, all containing one layer. The end result is understandably a bit clunky looking.
Unless I’m mistaken, however, and perhaps Andrew has already considered this route but dismissed it for reasons I haven’t figured out, there is a conceptually simpler way to construct the reflector script, involving multiple <GroundOverlay> elements inside one folder (which is allowed), each of which holds an individual layer that can be turned on or off separately. This is what I did for the Canada reflector script [txt], and it means you only need one network link, and it can be at the top layer in your Places. (The full post, with KMZ network link)
As for HTML legends — these are nice, but if you’re not so wedded to it having to be HTML, then you’ve already done most of the work if you make a PNG out of it, and then display that as a ScreenOverlay. Here is an example using Andrew’s PNG [KMZ]. All we need then is a web service that turns HTML into a PNG and returns it, and we’ll suddenly have a nice pipeline for generating floating legends for Google Earth. Of course, there are no links this way, but you could keep those in the descriptions in the Places window.
7. The XSL Stylesheet is extremely cool, and it is exactly what WMS needs for automated delivery to Google Earth. Jeremy at Mapdex, is that something you could use to generate a network links with component <:GroundOverlay> tags for layers, much like you did with ArcIMS?