Satellite imagery taken at a 45 degree angle was added to Google Maps in 2010. Bird's Eye View enables you to get an alternative look at selected locations. The 45 degree angle view is not available across all of the areas covered by Google Maps, and is mostly restricted to larger cities. You'll need to activate the newer MapsGL technology in your browser before the Bird's Eye View layer becomes available.
Open Google Maps in your browser. If you have not already upgraded to the MapsGL version of Google Maps, which includes support for 45 degree imagery, you'll see an "Experience MapsGL" heading on the left. Click "Try it now" to activate the feature.
Navigate to the area you'd like to view using the pan tools in the top left corner or clicking and dragging using the mouse. Click the "+" button or use the mouse scroll wheel to zoom in to the map at a specific point. If you reach the Street View interface, you've zoomed in too far.
Click the "Satellite" button in the top right corner of the map if you are not already viewing satellite imagery. Open the drop-down menu below it and select "45°" from the list to activate the bird's eye view. If the option is greyed out, either you need to zoom further into the map or the current area does not support the layer.
Click and drag around the navigation ring in the top left corner to change the direction the map is viewed from. The 45 degree bird's eye imagery can be viewed from the four points of the compass, so it's possible to rotate around a particular landmark or building.
In most cases the 45 degree bird's eye view appears automatically when you zoom into a supported area using the satellite view. You can toggle the standard overhead view or the 45 degree angle using the "45°" option on the layers drop-down menu.
With the 45 degree angle imagery activated, you can still pan around and zoom in and out of the map. Once you've zoomed out to a certain level, or panned beyond the area covered by the bird's eye view photography, the standard satellite imagery takes over again.