Aerial Vegetation Survey
Ryan Becker, Project Leader
The Forest Service is confronted with a multitude of challenges to preserving the resources contained within National Forest boundaries. One emerging challenge that defies a simple solution is controlling the spread of invasive plant and animal species. Invasives can threaten entire ecosystems, and frequently require rapid, sweeping control measures to prevent massive destruction.
The islands of Hawaii present an opportunity to view the destructive potential of invasive species. Recent and ongoing volcanism continues to form the island chain in one of the most remote locations on earth, but the tropical latitude of the islands, combined with a wide spectrum of precipitation characteristics, allowed a curious mixture of plants and animals to flourish and adapt to the unique environment. The biological isolation was shattered following the advent of open ocean seafaring, and previously landlocked exotic plants and animals continue to find their way to the islands in the cargo holds of ships and planes and in the possession of unassuming tourists. Species from other parts of the globe now arrive in Hawaii about one million times more frequently than they did before human seafarers discovered the islands. Refer to the State of Hawaii's discussion of invasive herbaceous species here for more information.
Those battling invasive species seek accurate, up-to-date information about the exact locations of the invasion in order to maximize the effectiveness of potential treatments, minimize costs, and avoid possible unintended side effects. Space-based satellite imagery is generally not detailed or current enough to offer useful information on the exact locations of invasive species. Manned flights, either by airplane or helicopter, are expensive and labor-intensive, and the data is often time-consuming to plot on maps. Ground-based surveying is very labor-intensive, requires that all surveyors be trained in recognizing the species under study, and in many parts of of Hawaii, is simply not possible. SDTDC has been searching for products capable of overcoming some or all of the drawbacks to the existing surveying methods.
FY 2003 Planned Actions:
- Locate existing technology with the potential to mitigate some or all of the constraints to current invasive species surveying techniques.
- Field test potential technologies in areas with partial previous surveying to evaluate the quality of the collected data.
- Report on the potential of the chosen technology.
The Bat 3, built by the MLB Company, of Mountain View, CA, performed eight flights over selected areas in and around Hawaii Volcanoes National Park during a one-week test in June 2003. Geo-referenced digital aerial photos displaying various resolutions (to a maximum of two inches per pixel) were collected and provided at the end of the week. The aircraft collected imagery under cloud layers and in windy conditions. Each flight lasted one-half to two hours and imaged between 60 and 400 acres. The memory of the onboard camera limited flight durations; aircraft fuel and battery reserves allow flight durations as long as six hours.
The Bat 3 has a six-foot wingspan, average total aircraft weight of 15 pounds, and packs into a 24-inch by 48-inch case. The base station includes a 900-mHz spread-spectrum RF modem for real-time communication over as much as three miles' separation, a laptop PC with all required software, and a video recorder to view and record live video feed. The system sells as a complete package, including training, for $42,000. MLB also provides imaging-on-demand services at competitive rates. Contact MLB for current pricing.
The test system deployed in Hawaii used an inexpensive commercial digital camera to record images. The processing software developed by MLB provided a GPS reference for each image, but orientation, angle, and lighting differences made orthorectification of the images time-consuming. See the mosaicking page for detailed information on project accomplishments involving image mosaics.
Individual image quality and resolution will also improve with the introduction of better digital recording equipment. The cost of upgrading the camera used to record the images is nominal in comparison to the overall system cost, and will allow collection of higher-quality data under less demanding flight conditions. See the image resolution page for more information.
A variety of competing equipment offers similar capabilities, but restrictions related to the status of UAVs is under FAA rules have dissuaded many manufacturers from making their products commercially available for this purpose. Various UAV advocacy groups have been collaborating with the FAA to develop new rules. Both the FAA and UAV proponents expect success within the next couple years, which should lead to rapid growth in the market for such services. For more information about other candidate UAVs, see the other UAVs page. To learn about FAA requirements, visit the FAA issue page.
Project managers in Hawaii chose areas to be imaged and scouted potential takeoff/landing locations over a period of approximately two months before the flights. MLB consulted on aircraft requirements during this period, and ultimately, all areas the managers requested were imaged, including one plot that was not discussed with MLB until the day before the flight. The extensive vegetation and deficit of open areas devoid of aerial hazards such as power lines in the project area are common challenges to unmanned vehicle flight in areas of interest throughout the Forest Service, and the tools and techniques MLB uses in these situations allows safe operation in challenging conditions.
MLB downloaded and shared the raw files and ephemeris data with the project managers immediately after the flights. Individual images could be placed on a basemap and manually feature-matched, which allowed same-day evaluation of the quality of the data, as well as investigation of small areas of particular interest. It is difficult to assign an absolute value to this data, as the project managers had never had access to such a product before.
Orthorectification and mosaicking of the collected data would allow users to exploit the tools of GIS software to more rapidly extract information from the data. An example of the manual mosaicking performed during this project is available here. The company that performed this work, Forest One, Inc. of Itasca, Illinois, provided two mosaics from a total of 71 images after about two weeks' work. The change in color in the example is a reversible artifact of the processing. Also notice the obvious field-of-view-induced "cauliflowering" of the image, and the reduction in resolution from the original photos. Images with more overlap would yield higher-quality mosaics.
UAV-collected imagery is comparable to both satellite imagery and manned-flight imagery. It holds the promise of high data quality at low cost. While neither the hardware nor flight plans used in Hawaii were optimized for such a mission, both the raw data and the orthorectified, mosaicked images cost less than the Ikonos imagery used as the basemap during mosaicking. UAVs may quickly grow into widely-used aerial mapping tools once the FAA establishes UAV-specific rules. In the interim, projects such as these can provide high-quality data in moderately-sized areas for less cost than manned flights.
This project is complete; however, the Forest Service Remote Sensing Applications Center (RSAC) is continuously monitoring the UAV industry for advances that have relevance to Forest Service business in any field. See the Links page for a paper summarizing RSAC's mission in monitoring UAV technology, or contact RSAC for current project information.