As already mentioned at Google Earth Blog, Google Today announced at their Google Geo Developer Day, version 4 of the client. The first noticeable thing is the UI had undergone a radical revamp, (in fact see images at OgleEarth and the Google Download Site), my favorite the tri-state tickboxes!, there are are tweaks to the inbuilt layers and terrain.
However most interestingly (for me), is the new KML features. Firstly 3D models can now feature textures, (using Collada XML file format), which introduce a new ‘object’ type for Models.
NetworkLinks, Overlays and placemarks, can all specify a Region that they apply to. Firstly it can conserve bandwidth by only fetching network links when the area that the link knows about is in view. But it also extends to make nice ‘Streaming KML’(tm) layers, that can incrementally load in imagery as you zoom in, so you can create a nice image layer (eg) much like the inbuilt imagery.
Also individual placemarks, overlays and even folders can have Level of Detail information specified, which can greatly improve the presentation of many layers, without resorting to server tricks to manipulate the data.
There is also the beginnings of support of for ‘Updates’ via network link, so the whole content doesn’t have to be refreshed each time, just ‘incrementally’ updated, haven’t got this to work yet.
Also in the News: Google Maps API had added Geocoding for US, Canada, Japan, France, Italy, Spain and Germany (other contries to follow). {edited to add:} Also you can overlay KML’s directly in Google Maps, Neat! (that link is a demo of overlaying recent images from Geograph!)