Wednesday, March 21, 2007

Placing Custom Aerial Photography

This morning I had some fun with an aerial photograph taken by a colleague here at Google. She shared one of her excellent photographs which depicts the coastline of Santa Cruz, CA as seen from the cockpit of a small plane. I placed the image as an overlay in Google Earth, but as this image was not of the landscape at a 0 degree tilt (i.e. looking straight down), I had tweak and stretch the image a bit to place it. Additionally, I used the Snapshot View command to capture an appropriate view point in Google Earth.

I posted this as a KML file so that everyone could take a look. Let me know what you think.

I was only somewhat successful, as the overlay is not an exact match to ground features. Notice the roads and some other features are not aligned. Anyone else want to open this file and edit the overlay yourself? It is tricky, but very fun!

7 comments:

Lauren said...

I think you did about as best as could be done with the limited stretch operations available. Georeferencing overlays is tough and most professional GIS apps apply a complex series of transformations and point matching to warp the image into shape. I do think it helps to turn the overlay transparency down to make it easier to line up points.

But I don't think it needs to be perfect - as it is, the perspective view provides a lot of information that you don't get with the base imagery. You can see that the prominent structure is actually a lighthouse, for example.

John said...

Thank you Lauren. Yes, as you mentioned, the perspective that an alternative angle photograph provides can be both useful and interesting. It is also nice to see the sides of the cliffs which are otherwise distorted when you tilt the view in Google Earth.

Working on that overlay made me want to jump in a small plane and take some pictures!

raghu said...

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Dirk said...

Hi John,
That's a nice shot and overlay - the other day I was on a transatlantic flight to San Francisco and did some 'aerial photography' of my own - I had a window seat and we were flying above the Arctic, my GPS had reception and I took a bunch of shots of these beautiful glaciated fjords I could see through the little window - using the georeferencing on MTBGuru I later found out the photos were of Devon Island aka 'Mars on Earth'. Here's the kml file...

Bob said...

I wonder if you could use some image morphing software to correct this. Have the airplane shot be the 'before', and the satellite perspective be the 'after'. Set up some match points, and replace the after shot with the with before shot, so you use the same image when you tell it to do the morph.

(The last time I used a GPS on a flight I got chewed out by a stweardess...)

Dirk said...

I was a bit weary about using the GPS on the plane as well but why should they mind? It's only a receiver in the end, I'm sure any laptop spews out orders of magnitude more radiation, if that would be the concern...

Imanuel said...

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