Somehow I found myself on the Virtual Earth blog and found the post on ‘Microsoft corking the bat’ quite interesting:    

If you think applications like Virtual Earth and Google Earth are simply fed raw data from remote sensing systems and manage to present the experiences they do you’ve been watching Minority Report too many times 🙂 Tweaking doesn’t even come close to doing justice to the enormous production process to get data from sensor to web. It’s understandable that most of us are completely unaware of this process; there would be a lot more vegetarians if we all had to kill what we eat. In the same way we are insulated from the gory details of the journey from farm to grocer, we don’t need to understand how to process imagery and data models of the Earth’s surface if all we want to do is cruise around in Virtual Earth and enjoy the experience. To appreciate this beautiful image of Niagara Falls we don’t need to be aware of the image processing that went into creating it:

1. UltraCam is flown and captures the imagery with a prescribed set of overlap
2. Pre ortho processing – ingest formatting, pan-sharpening (mutispectral brought to panchromatic resolution), radiometric normalization (images brought to similar spectral range)
3. Orthorectification (surface and camera distortions removed from imagery and images are geographically referenced to a coordinate system)
4. Orthomosaic (individual ortho images seamed and color balanced together)
5. Final radiometric look up table (final spectral adjustment applied to entire mosaic)

The Virtual Earth team employs lots of people whose job is to make the sensor data collected represent the Earth as best as possible where automation breaks down. Rob Waterman is one of these guys. I asked Rob what goes into creating elevation models of the Earth’s surface:

My goal is to make the data represent real life as best I can. Specifically for Niagara I used three different input DEM sources and some well placed breaklines etc. to generate a single improved DEM for the area.  There is nothing "fake" about it.  I combined the best of all the data sources available to me to come up with the most realistic representation of the area (including ortho imagery for breakline placement and many oblique photos to help determine the most accurate/representative layout of the area).  I think we are here to generate the most accurate/realistic Virtual Earth we can and that means using the all the data available in an attempt to arrive at the "truth".

Read the full entry here. Check out the Niagara Falls pictures here. Beautiful.