Sydneysider Andrew Hallam posts a long and detailed evaluation of Google Earth on his Digital Earth Weblog. He approaches the application from the perspective of a GIS professional contemplating using it for his work. It’ a fascinating and nuanced read, and amounts to some great free feedback/feature requests that Google would be remiss in ignoring.
Andrew is impressed by the network link, however. I wonder why there wasn’t such a thing before in GIS land (is there?) The idea of the network link is great, but it is “just” an XML feed applied to a spatial coordinate system. Wasn’t there ever any need for that before? How did (do) GIS pros deliver oft-updated and even dynamically generated data to a wide set of subscribers?
“Andrew is impressed by the network link, however. I wonder why there wasn’t such a thing before in GIS land (is there?)”
ESRI’s desktop software has had this link for years, and you can subscribe to datasets via ArcWeb Services. Not many people take advantage of this though because of bandwidth issues and the cost of subscriptions. Google can afford the huge costs of their digital image archive (I can’t even begin to imagine how much they paid for it, but its millions I’m sure). My company used to subscribe to data, but it was much easier to just buy a CD “dump” and use that (and cheaper).
“The idea of the network link is great, but it is “just” an XML feed applied to a spatial coordinate system. Wasn’t there ever any need for that before?”
ArcIMS (another ESRI product) has used what ESRI calls ArcXML. It’s been around for over 5 years. UMN Mapserver has a similar method. We’ve all been using XML for web mapping since as long as I can remember.
“How did (do) GIS pros deliver oft-updated and even dynamically generated data to a wide set of subscribers?”
Basically you can subscribe to ESRI’s ArcWeb Services or take a look at the ESRI Geography Network to see how “pros” do it. Our datasets are usually too large to do analysis upon so people usually just buy DVD/CD versions of the data sets. You can download much of what we use free (Good example is the U.S. State of California’s Spatial Information Library), and preforming GIS analysis over the internet is very bandwith intensive (even over the LAN it is sometimes very difficult).
James is correct. There is nothing new about networked access to spatial data in the GIS world. There are a variety of methods for achieving this, depending on whether you want a map image (a GroundOverlay in Google Earth terms) or spatial features (points, lines and polygons).
In my post, what I was trying to say was that without the ability to bring in data from external map services Google Earth would be much less interesting, to me anyway. Network links open up a lot of options.
I’ve started working on a “less nuanced” wish list of enhancements to Google Earth that address some of the issues that I’ve raised. Most of the items on the list are just stuff that most GIS people deal with every day, with some minor variations due to the 3D environment.