An ABL That Maps Ecosystems

An airborne laser and hyperspectral remote-sensing platform is reinventing the science behind natural resource management decisions and is the most significant new tool since the advent of aerial photography a century ago, said Allan Smith, interim chairman of Hawaii's Department of Land and Natural Resources (DLNR).

CAO Lidar: Forest and pasturelands (Image courtesy Carnegie Airborne Observatory)

The system -- the Carnegie Airborne Observatory (CAO) -- combines spectroscopic imaging and waveform laser remote sensing technologies to study regional ecosystems anywhere in the world. The CAO mission is to understand how land-use change, climate change and natural disturbances are affecting the structure and function of ecosystems, and how these changes alter the services provided by ecosystems to people.

The CAO employs several cameras mounted in an aircraft, which is flown over the landscape to produce 3-D images of the forest canopy, the earth and everything in between. The instruments are so precise they can measure the height of individual trees, the distribution of invasive weeds in the understory and geological formations that had previously been undetectable from the air. The instrumentation can be used in a wide variety of fixed-wing aircraft found around the world, according to the CAO Web site, and is currently being deployed in the Hawaiian Islands.

Designed to make regional assessments of the carbon, water and biodiversity services provided by ecosystems to society, the CAO can capture detail extending from the forest canopy to the ocean floor. It is especially useful for modeling forest, hydrological and marine cycles and ecosystems. The system is becoming a major factor in shaping management actions for terrestrial to marine environments, its creators said.

Smith said, “Managing Hawaii's natural resources is challenging. Every day, we are called upon to protect the forests, rivers, reefs, plants, animals and the cultural heritage of these precious islands. The public expects us to base our policies and actions on the best science that is available to us."

CAO Hyperspectral + LiDAR: Institute for Pacific Islands Forestry, Hilo, Hawaii (Image courtesy Carnegie Airborne Observatory)

Greg Asner, director of CAO, is conducting a public presentation about the technology today at 2 p.m. at the Hawaii State Capitol auditorium. The presentation is co-sponsored by the Hawaii Statewide GIS Program, the DLNR Div. of Forestry and Wildlife and the Hawaii Geographic Information Council.

Asner is a faculty member of the department of global ecology at the Carnegie Institution of Washington and of the department of geological and environmental sciences at Stanford University. His scientific research involves the way human activities alter the composition and functioning of ecosystems at regional scales. His most recent work includes satellite monitoring of selective logging and forest disturbance throughout the Amazon Basin, invasive species and biodiversity in Hawaii rainforests and El Nino effects on tropical forest carbon dynamics. His remote-sensing efforts focus on the use of new technologies for studies of ecosystem structure, chemistry and biodiversity in the context of conservation, management and policy development.

CAO can fly in two distinct modes, depending on user needs. The CAO Alpha can map nearly 50,000 acres per hour at a spatial resolution of 1 to 2 meters. (Even higher spatial imaging can be accomplished when required by the scientific study.) The CAO Beta is intended to fly larger regions with a more complete spectral sampling at 4 to 5 meters spatial resolution.

Alpha, the CAO primary configuration, is comprised of an integrated imaging spectrometer (hyperspectral sensor) and a small-footprint scanning-waveform light detection and ranging (lidar) system. The imaging spectrometer is a custom-built visible near-infrared (NIR) pushbroom imager using the Offner spectrometer design. The spectrometer has a swath of 1500 pixels and can be programmed in-flight to acquire imagery in up to 288 channels of 1.8-nm bandwidth (FWHM) covering the 400- to 1050-nm wavelength range. The spectrometer is comounted on a stabilized plate with the scanning lidar operating at up to 100 kHz with full waveform digitization. The lidar simultaneously collects discrete-return and waveforms on separate data systems. Together, these instruments provide detailed, high spatial resolution 3-D information on the structure, biochemistry and physiology of vegetation and ecosystems.

The beta configuration, for use When spectroscopic data beyond 1050-nm is required, the CAO lidar can be integrated with the full-range Jet Propulsian Laboratory's airborne visible and infrared imaging spectrometer (AVIRIS). This mode provides spectral information in the 400- to 2500-nm wavelength region along with high-resolution waveform lidar data. Unique data "bundling" algorithms provide a way to automatically colocate the CAO lidar and AVIRIS imagery.

CAO science and research partners are the Institute for Pacific Islands Forestry, Pacific Southwest Research Station, US Forest Service; the CTARS Laboratory at the University of California, Davis; and Stanford University.

Engineering and data processing partners: Analytical Imaging and Geophysics LLC of Boulder, Colo., a provider of remote sensing and geophysics research and services; Imspec LLC, a Palmdale, Calif., developer of Atmospheric CORrection Now, or ACORN, atmospheric correction software; ITRES Inc., a Calgary, Alberta, and Englewood, Colo.-based maker of spectral and hyperspectral imaging sensors; NASA's Jet Propulsion Laboratory at CaltEch; and Optech Inc., Canadian developer of the anairborne laser terrain mapper (ATLM).

The effort is supported by grants from the W. M. Keck Foundation and William R. Hearst III.

For more information, visit: cao.stanford.edu