Small Format Aerial Photography;
Schermerhorn Park in Galena Kansas

Paul H. Lewis

27 Jun. 2008

in fulfillment of requirements for

ES 555, Small Format Aerial Photography

Table of Contents
Introduction Aerial Photography
Image Processing Conclusion

INTRODUCTION:

In the fall of 2007, The Earth Science (ES) 546 Field Geomorphology offered the opportunity to utilize a blimp and kites to take small format aerial photos of various Kansas physiographic regions. ES 555 presents opportunities to take those photos and explore different techniques to manipulate them to enhance the imagery. ES 546 had two field episodes, of which the second period was conducted from 25 - 28 October. During one particular trip, the class visited southeastern Kansas. In particular, we stopped at Schermerhorn Park, along Shoal Creek just outside of Galena Kansas. At this location, we had an opportunity to do some small format aerial photography using a tethered blimp. For this report, I will stitch some of the imagery to create a birdseye view of the park and surrounding area. Blimpworx website presents many reasons why blimps are an excellent tool for attaining aerial photographs.

AERIAL PHOTOGRAPHY:

Weather conditions were ideal for using the blimp. Partly to mostly cloudy skies with high thin cirrus provided ideal lighting conditions. Calm to light winds, made it ideal for launching the blimp at Schermerhorn Park. This was perfect since the close proximity of trees in this park, kite aerial photography (KAP) would have been problematic (Aber and Aber, 2002). A Canon S70 and Rebel cameras and radio control units were utilized at this location. The radio control unit turned, tilted and controlled the shutter of the camera. Figure 1 gives a better view of the picavet and camera controls. The blimp is filled with helium as seen in figure 2 and the camera rig is hung from the tether mount under the nose of the blimp as seen in figure 3. Once the set up is complete, the blimp can be launched and flown up to approximately 500 feet without FAA approval (14 CFR Part 101). Figure 4 is a picture of the blimp in flight, this particular picture was taken while we were photographing Big Brutus.

Figure 1: Dr Aber holding the picavet with the S70 Camera rig.
Image taken by Paul Lewis (2007).
Figure 2: Dina Wingfield (Geobuddy 4) filling the blimp with helium.
Image taken by Paul Lewis (2007).
Figure 3: Tyler Ringler releasing the camera as the blimp is launched.
Image taken by Paul Lewis (2007).
Figure 4: Blimp: 13 ft that requires ~250 cubic feet of Helium, able to lift 7 lbs, best operated in calm to light winds (< 10 mph). Note spider stringers on the tether! Image taken by Paul Lewis (2007).

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IMAGE PROCESSING:

I've taken a series of three images from the Canon S70 (figures 5 - 7) from the trip that show state route 26 extending from horizon to horizon. I used a demonstration version of PTgui to stitch the imagery together to produce one panoramic view of the highway. This demo version of PTgui only allows panoramic views on a cylindrical form.

Figure 5: State route 26 bridge crossing Shoal Creek at Schermerhorn Park.
Image taken by ES 546 Class (2007).
Figure 6: Wood lot and farm south of Shoal creek and Schermerhorn park.
Image taken by ES 546 Class (2007).
Figure 7: Schermerhorn park entrance off of rounte 26.
Image taken by ES 546 Class (2007).

Figure 8 gives a fairly accurate panoramic view from the south through north of route 26 passing to the west of Schermerhorn Park. With the demo version of PTgui, three images were essentially the limit of stitching that could be accomplished before the image became distorted and difficult to view. I believe tiling images of the park, creek and wooded areas could have produced interesting results, but the demo version would not permit anything but panoramic views.

Figure 8: Panoramic stitched view of State Route 26.
Image stitched by Paul Lewis (2008).

Next, I used GNU Image Manipulation Program (GIMP) to adjust the image brightness and to sharpen the image. Figure 9 is the post processed version of the previous image. Adjusting the brightness stretches the color values. Stretching the color values or brightening the image makes the color appear more vibrant. Sharpening was accomplished using the "unsharp mask" filter, which essentially increases the contrast of the image in areas of abrupt increases of intensity. This will make distinct changes in the appearance of tree branches and road edges, but little differences in homogeneous areas like farm fields and tree canopies.

Figure 9: Post processed panoramic view of State Route 26.
Image enhanced by Paul Lewis (2008).

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CONCLUSION:

I believe a birdseye view of Schermerhorn Park could have provided an interesting perspective for this visit. Due to the demo software limitations, creating the birdseye view was not possible. Nevertheless, I was still able to enhance the brightness and sharpen the image for improved viewability. Panoramic stitching was also possible and utilized to create imagery showing a large expanse of area west of the park. Despite the set backs of the demo software, this project has still been rewarding.

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REFERENCES:

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Comments to plewis2@esumail.emporia.edu