ES 555 Lab Exercise
Panoramic Imagery

Cheyenne Bottoms, Kansas
James S. Aber


Introduction

Panoramic photographs have a long history in aerial photography beginning with George R. Lawrence early in the 20th century--see panoramic photos. A true panoramic photograph shows 120° or more of the horizon with little geometric distortion. This is accomplished by rapidly rotating (panning) a slit lens, which sweeps the light exposure along a strip of film mounted in a semi-circular fashion. Panoramic cameras are available today, but are difficult to adapt for small-format aerial photography.

A composite panoramic image can be constructed from a series of overlapping individual frames that are stitched together and projected in cylindrical format. This technique works best if all images are about the same scale, the horizon is roughly level, and each photo displays comparable lighting conditions.

This exercise is based on five kite aerial photographs from Nature Conservancy land at Cheyenne Bottoms, which is a large wetland complex in central Kansas. The images were acquired in July, 2004, when the marsh pools were full of water and wet meadows were green with vegetation.

More examples and background information about
the geographic setting--see Cheyenne Bottoms.

The images were taken with a Canon Digital Rebel SLR-style camera with an 18-mm lens (~28 mm film equivalent). The original 6 megapixel images (3072x2048) have been downsized to 1600 by 1067 pixels for purposes of this exercise. The files are named cb1 through cb5. Transfer these jpg files via FTP into your personal computer work space.

All the pictures were taken from the same vantage point looking toward the horizon. The five overlapping images encompass views toward the west, north, and east.

Individual raw input images of Cheyenne Bottoms, Kansas.

CB5, view west

CB4, view NW

CB3, view north

CB2, view NE

CB1, view east

The exercise involves two software packages for different phases of the image processing. Both were utilized in the previous exercise--see lab 5.

  1. D Joiner -- Designed for stitching together photographs in mosaic and panoramic views. From D Vision Works.

  2. Adobe Photoshop -- Industry standard software for manipulating and enhancing photographic images. See Photoshop.

Note: This exercise is based on D Joiner, available in the Geospatial Analysis laboratory at ESU. Distance-learning students may utilize another image stitching program called PTGui. Trial software is available free for 30 days.

Exercise

To begin, take a look at the five raw images in Adobe Photoshop. Notice different overall brightness levels. Such variations are inherent in pictures taken in different directions relative to scene illumination by the sun. Variations in cloud cover and cloud shadows also affect scene brightness. Notice, for example, that cb1 is quite a bit brighter than its neighbor, cb2.

Next adjust the overall brightness of each image using "Image: Adjust: Levels" as you did for exercise 1. Some images need to be brighter, others darker. Try to achieve roughly comparable brightness for all the images. Also carry out sharpening of the images. Save the resulting images with different file names from the original files.

Now you are ready to build a composite panoramic image. Click on the D Joiner icon to start the software, and then maximize the working window to fill the entire monitor screen. Click on the file menu (upper left corner), then choose the "Insert Photos" option. Select the five images you just created, then click the "Open" button. You will next see a box titled "Matrix." Accept all default entries, and click OK.

At this point, you should see the five images positioned side by side. The images should be arranged in the same order from left to right as shown above. If they are not in this order, rearrange them. Simply click on an image and drag it to the proper position. In this process, the image set as the origin may have shifted. Highlight the center image as the origin--right click on the center image and select "Set as origin."

Having set up the images in correct position, you can proceed to the "Marker mode" for stitching images together. Begin with the origin (center) image and work to the right or left (right & left arrow keys). Three markers should be sufficient to join adjacent images. Check your progress at each stage with the "Preview mode," and save your composition periodically. Note: make sure to save the dst file in your own student working folder.

As you add more images to the panoramic composite, it will expand sideways and become impossible to see the entire image in one view. You can shift the display portion by clicking and holding the mouse cursor to the left or right while in the "Preview mode." The scene geometry is quite distorted in this mode. Continue this process until all five images are incorporated into the composite.

To create a projected panoramic image of your composite, select "File: Export: Cylinder" from the menu. Name your file cb_pan. When the "Stitcher options" window appears, accept width and height default values. Slide the JPEG Quality marker to midway, and click OK. View the resulting image with Adobe Photoshop. You should have a panoramic image similar to the example below.

Sample panoramic image
Cheyenne Bottoms

To complete the exercise, prepare a final image to turn in. Crop off the blank margins as much as possible without removing too much of the actual scene. Annotate the image with a title, your name, and directions of view. Note: do not place text across the horizon, which should be clearly visible.

Turn in

Return to SFAP schedule.
ES 555 © by J.S. Aber (2008).