Peter Miller wrote: > I get the impression that rectification gets a lot harder as the angle > gets more slight and it is clear to me that a camera pointing straight > down would be the most useful device going forward. Not easy to do. You can't legally modify an aircraft at all without invalidating its certificate of airworthiness, so where to mount the camera? > The time of day is also important to avoid long shadows. Generally an overcast day reduces the contrast to make the photos easier to use, but shadows can actually be very helpful. They give an impression of height for some things. For archeology shadows sometimes showed medieval ridge and furrow field systems and the edges of roman building platforms. Winter time when there are no leaves on the trees will reveal much more detail. The true route of roads and streams are easily hidden by tree cover from the air. Calm winter days often are less turbulent than summer days so the 'plane as a platform is steadier. (Clear blue skies in summer can be VERY bumpy in the air). > I am pleased that this project is creating some useful discussion > which we should continue to see what we can extract from these images > and what we can learn going forward. > > Tools to process images and to host rectified images seem to be pretty > crucial to take full advantage of all this. > > Fyi, I have added comments to some images to say what it is of, the > bearing the image was taken at, and the appropriate link to OSM.
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