After the balloon mapping trip at Big Branch National Wildlife Refuge on May 14th 2012, I created two 3-D images out of four images captured during the flight using a very easy photo editing technique. This can be done with any photo editing software that can separate images into RGB channels (I used Photoshop).
First, a bit on how 3-D works: We see 3-D with our everyday vision because our eyes are separated and essentially process two different images from slightly different vantage points. A camera, however, does not have these “two eyes,” and so to see an image in 3-D, we have to take shots from different vantage points and combine them into one- a process that our brains do to see 3-D.
How far apart do the images have to be? Normally, just the distance between your eyes will suffice, because this is the process that we are trying to mimic, but with balloon mapping, this distance increases because the camera is significantly farther away from the subject than normal photography. A good rule of thumb is to use photos that are separated by 1/30th the distance away from the subject. So, if you are flying at 1,000 feet, choose images that are roughly 33 feet apart. You can estimate this by looking at objects you may recognize in the photo and using their dimensions to measure, or by using ground-control points, among other methods (see example images below). For the Big Branch trip, I found that images about 7-10 images apart from each other in a continuous set worked well (at a final flying height of around 1,000 feet).
Here are the steps: 1) Choose your two images making sure they are separated by an appropriate distance. 2) Open them with a photo editing software and paste them on top of each other. 3) Auto-align using an auto projection. 4) Duplicate and paste the top image into its own new document or window. Delete the duplicated layer from the previous window. 5) With the duplicate image in the new window, select and copy only the red channel (turn off the blue and green channels-the red channel alone will look black and white). 6) Return to your original window (with the image that was never duplicated), and turn off the blue and green channels. 7) Select the red channel and paste the new red channel (from the duplicated image) to replace it. 8) Turn on all the channels and crop out anything you may not want (such as the excess red channel along the edges). 9) Put on your 3-D glasses (you can make your own) and view your 3-D photograph. Make sure you keep the red lens on your left eye and the blue lens on your right eye.