Author
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Thomson, Steven |
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Submitted to: Biannual Workshop in Color Photography and Videography in Resource
Publication Type: Proceedings Publication Acceptance Date: 12/15/2003 Publication Date: 12/6/2004 Citation: Thomson, S.J. 2004. Potential and limitations of low-cost imaging and georeferencing methods for agricultural aircraft. Proceedings of the the 19th Biennial Workshop in Color Photography and Videopgraph in Resource Assessment. American Society for Photogrammetry and Remote Sensing Proceedings. CD-ROM, paper number 0025.pdf, 4 pg. Interpretive Summary: Precision application is the practice of applying crop inputs such as pesticide, nutrients, or water only to field areas requiring those inputs. This practice has the potential of saving on chemical costs and reducing load to the environment. Costs of equipment, image processing, and image interpretation for implementing precision application has limited widespread adoption of this practice. Remote sensing from aircraft or satellites is used to detect field variables so precision application devices or irrigation systems can then be programmed with a "prescription" for application. For practical detection of field variables, it has become apparent that low cost but effective remote sensing systems are needed for more widespread adoption of precision application techniques. With this in mind, two simple imaging systems have been developed and evaluated on an agricultural aircraft platform. Advantages and limitations of each system for suitable detection of field variables are outlined. Use of digital video as an advantageous method for detection of deleterious algae in catfish ponds is outlined. Procedures for obtaining pond images and use of low cost software detailed for mosaicking images are detailed. Example data are shown correlating chlorophyll with digital numbers obtained from the image. Good agreement between image data and water samples has been obtained in preliminary studies. A high resolution, programmable digital camera has also been used in imaging studies. The camera worked well for imaging, but the pilot was frequently unable to image the correct portion of the field due to delays in shutter response. An automatic triggering device is proposed for programming the digital camera based on Global Positioning. Potential improvements to both imaging systems are discussed in terms of practical remote sensing from agricultural aircraft. Technical Abstract: Two low-cost digital imaging systems are being used on agricultural aircraft for remote sensing research projects at the Delta States Research Center, Stoneville, MS. One imaging system uses digital video with near-infrared (NIR) imaging capability. The system was designed so interference filters could be changed easily between flights. Images were georeferenced using commercially available hardware that sends Global Positioning System (GPS) data to the audio track of videotape. A second imaging system uses a high-resolution digital camera with electronic remote trigger that can be activated by the pilot. Georeferencing was accomplished using a GPS interfaced with the camera and implemented using a Flashpoint Digita® software script. In experiments, shutter delay caused the pilot to miss desired targets, but the pilot was able to compensate by activating the shutter early over specific landmarks. To remove the pilot from operating the camera, an automatic GPS-activated shutter is proposed. The shutter will trigger based on GPS position with look-ahead capability to compensate for both shutter delay and GPS latency. Although simple imaging systems are convenient and have shown great potential for detecting field features, limitations in image resolution, limited GPS accuracy in the direction of flight, and the need for time-consuming mosaicking of images taken at slightly different altitudes may require innovative solutions for rapid image processing and interpretation. An example application of imaging catfish ponds for deleterious constituents is outlined, and possibilities and limitations for both imaging systems are discussed in terms of practical remote sensing from agricultural aircraft. |
