Aerial QTVR Panoramas
After playing around with ground-based immersive bubble panoramas using the Nikon Coolpix 8400 with its companion FC-E9 fisheye conversion lens
I was eager to get the gear in the air to take the aerial equivalents. I have long admired Scott Haefner’s series of aerial QTVR bubble panoramas. Scott built on a techinique first described by Philippe Hurbain.The technique is a little different from that used in the ground-based panoramas in that it involves only two fisheye images. The kite-lofted camera takes a fisheye image pointing straight downward and this is joined with a fisheye image of the sky looking straight upward. The seam between the two will occur at the horizon juncture between land and sky. Back home these two images are converted to equirectilinear format, stitched together, and fed to the shareware program Pano2QTVR. The result is a Quicktime movie that can be embedded in a WWW page
as illustrated below.
Use mouse or arrow keys to turn the image. Shift key zooms in; control or option key zooms out. Scroll down a bit for an explanation of how these panoramas are assembled.
The pages subordinate to this page will contain one panorama per page and will serve as destination pages for panoramic images posted on our collaborative geo-annotation maps. At the bottom of the list I will include an explanation of the aerial QTVR process.
Posted QTVR images in reverse chronological order
Notes on how the Aerial QTVR panoramas are made
The key to my setup is the remarkable Nikon FC-E9 fisheye adapter. This lens attachment allows my Nikon Coolpix 8400 to see a circular image covering 183 degrees — slightly more than a hemisphere. The downward-facing aerial image captures the entire hemisphere below the camera. If you can persuade the camera to point straight down then the image will have a thin band of sky circling its periphery. Thus is captured the earth half of the panorama.
-
Camera flight from the kite is straightforward. You select a kite to match the wind and alunch it to an altitude of around 150 feet. You then attach the string and pulley suspension — a Picavet — and attch the camera cradle. After making sure the camera is in the correct mode, you activate the timing circuit and let the camera loose (with its large, curved front lens element pointing toward the decidedly rough ground.) Letting out more kite line sends the kite, and the attched camera cradle, higher until the desired altitude is gained. You can then walk the kite around to several positions while the timing circuit clicks away. On this particular outing approximately one in four of the images collected was pointing close enough to straight down to be usable in constructing panaramas.
Let me describe my panorama creation workflow on a Windows XP laptop computer.
My eight megapixel Nikon 8400 yields a circular fisheye image that is around 2300 pixels in diameter. Back at the computer I load the aerial fisheye image for a panorama into Photoshop. There I crop it to a standard sized square bounding the image circle, and save it back to the disk drive. For the next step I use PTGui, a graphic front end for Helmut Dersch’s remarkable Panotools program. In PTGui I am able to remap the fisheye image by designating the input image as circular, cropping each image to the image circle, and designating the output type as “equirectangular” with a 360 degree wide by 180 degree high field of view. I then repeat this process with the matching upward-facing sky fisheye image. The resulting rectangular image is quite distorted but it is just what we need for the next step.
I might note that I use an old ‘patched’ version of Dersch’s pano12.dll file in order to handle fisheye lens images. More recent versions of the file are limited to narrower views.
The sky fisheye image unwrapped to equirectangular coordinates.
The aerial, earth-facing fisheye image unwrapped to equirectangular coordinates
Now it is back to Photoshop with these two unwrapped images to join the sky to the earth. A first step is using the spot healing brush to remove objects that extend above the horizon in the sky photograph. The power plant silhouette is the most obvious intrusion. The joining is accomplished using a layer mask on the earth side layer.
The joined equirectangular images. Care was taken in aligning the sky image so that the sun was in the correct position. The exposure of the sky image was also adjusted (lightened).
The final step involves processing the equirectangular composite image to create a Quicktime Virtual Reality movie file. My first software for doing this was Panocube, an easy to use freeware program. It works just fine and is easy to use if you follow the instructions carefully. More recently I have been using Pano2QTVR for Windows, a program that seems more elaborate. It works well too.
And here is the resulting panorama. Go ahead and give it a spin: