Sometimes it's far more desirable to integrate the 3D scene with real live video footage than to build all the surrounding landscape. Not only is it easier sometimes but it can be far more realistic.
The process begins with shooting footage, normal aerial. Then a computer stabilizes the video. Following that one of our artists uses specialized applications to spot features in the video that are "tracked". This is done as a mixture of guidance by the artist and some very clever computer programming. The result from this is both clean video footage (required for the final composite) and 3D data that accurately represents the movement of the camera.
The camera is imported into the 3D scene and everything is adjusted to fit perfectly into the video footage. Then the animation, outlining the imported camera data is renderedout as a separate video file.
The new 3D video file is then overlayed into the stabilized video footage, and once a few more adjustments are made we have a perfect finished video.