Modeling directional reflectance spectra of coastal marsh vegetation

Modeling directional reflectance spectra of coastal marsh vegetation for remote sensing applications Dr. Michael Kearney Dr. Stephen Prince Dr. Michelle Hofton Dr. Robert Hudson Dr. David Tilley Proposal Defense Kevin Ross Turpie Dept of Geography University of Maryland 6 December 2006 1

Brackish and Salt Marshes CHARACTERISTICS: Important habitat for coastal flora and fauna. High primary productivity (0. 5 to 6. 2 kg C m-2 yr-1) (Day et al. 1989). Strong nutrient sink - reduces eutrophication. Sediment sink - reduces silting. Wave energy sink - protect coasts. Key pathway of detritus and CDOM to coastal systems. (Bouchard et al. 2003, Mendonca et al. 2004) • Salinity and hydrology produce characteristic zonation. • Inundated graminaceous and herbaceous monospecific canopies. 2

Brackish and Salt Marshes ISSUES: Sea level rise - drown marsh, increase erosion, change hydrology and salinity gradient. Disturbances § Storms - effect hydrology, nutrient flux, erosion. § Construction - effect nutrient flux and hydrology. Fire - can damage rhizomes, effects not fully understood. Invasive Species - can affect trophic, edaphic, hydological characteristics of the marsh. 3

Statement of Problem BRDF of vegetation canopies changes with wavelength, thus spectral features change with viewing and solar angles. This affects remote sensing techniques that depend on the marsh spectral characteristics (e. g. , classification). This can be compensated for with a canopy RT model, but water produces BRDF affects in inundated canopies that is not handed by current models. 4

Example: BRDF Effects from Water Data provided by Schill (Schill 2004). from Vanderbilt et al. 2002, with permission 5

Example: Spectral Effects of Water Spartina patens Schoenoplectus americanus 30 16 14 25 Water Level 20 15 Water Level Reflectance (%) 12 10 8 6 10 4 5 2 0 700 800 900 Wavelength (nm) Data digitzed from Stutzer 2004 1000 0 700 800 900 1000 Wavelength (nm) 6

PROPOSED THESIS RESEARCH Objective: Develop an RT model for the marsh canopy. Development - Build RT model on existing work. Validation - Validate the model against field data. Model Inversion - Test model inversion against field data. Closure Experiment - Test agreement of model, ground truth, and RS data. Geometric Optimization - Optimize viewing and solar angles for best vegetation spectral signature. 7

Role of a Marsh Canopy RT Model Remote Sensing Imaging Invert Model § Canopy Structure Integrate Model § Albedo § Light Field / FPAR Adjust for BRDF § Image Comparison § Classification § Vegetation Indices § Apps for RS § Geochem Cycling § Coastal Ecology § Productivity § Energy Budget § Climatology § Invasive Species § Dieback § Regn Monitoring Applications for RS Field Radiometry Adjust for BRDF § Standing biomass § Litter Decomposition § Productivity § Sub-lethal Stress § Tie to RS Imaging § Geochem Cycling § Coastal Ecology § Local Monitoring § Vic Cal § Validation 8

Marsh Canopy Radiative Transfer Model Selection Criteria Accounts for majority of variation in BRDF. Few input parameters. Invertible. Accessible code. Flexibility of design and implementation. Modifications Must add aquatic background (Water RT). May need to generalize for RS applications. Any parameterization done against training data. 9

i CANOPY Marsh Canopy Radiative Transfer Model t SOIL WATER Air-Water Interface 10

Marsh Canopy Radiative Transfer Model Sample of Existing Models 3 -D Ray-tracing Radiosity / Rectangular Cell Raytran Govaerts & Verstraete 1998, Kimes et al. 1984, SPRINT Goel & Thompson DART Gastellu-Etchegorry et al. 1996 Röhrig et al. 2000 1 -D Turbid Medium Geometric Optical Kubelka Monk 1931 Duntley 1942 Allen Gayle & Richardson 1971 Suits 1972 SAIL Verhoef 1984 DISORD Myneni et al. 1988 Kernel CR Kuusk 1995, 1996 MCRM Kuusk 1995, 1 -D (Markov Chain) IAPI Iaquinta et al. 1997 NADIM Gobron et al. 1997 2 -Layer Kuusk 2001 Ni et al. 1999 FLAIR White et al. 2001 Ross 1981 Strahler & Jupp 1991 Ross-thick Roujean et al. 1992 RPV Rahman et al. 1993 Walthall 1995 Ross-thin Wanner et al. 1995 Li-sparse Wanner et al. 1996 Bicheron & Leroy 2000 MRPV Martonchik et al. 2002 SGM Chopping et al. 2003 Hybrid SAIL-H Kuusk, Geo. SAIL Huemmrich 2001 García-Haro & Sommer 2002 11

Field Data Phase I - Locate sites and plan itinerary. Phase II - Measurements: Multiple monospecific canopy types. BRF on SPP from 60º to 60º. Plant R and T. LAI, LAD, Height. Soil and water samples - optics. Tide, weather, salinity. Digitial photos. 12

Validation and Closure Validation § Constrained optimization to fit model to validation dataset from field data. § Test hypothesis that model fitted input and results are within confidence intervals for observations. Inversion - Invert model for comparison with field data (no constraints). RS Closure - Compare with data at remote sensing scales. Key candidates: § AISA - airborne hyperspectral, with roll maneuver CHRIS / Proba - ESA sat with 5 angles, hyperspectral 13

Geometry Optimization Create “pure” vegetation spectral signature. § leaf reflectance and transmittance. § modeled BRDF for dense canopy and “black background. ” Create synthetic dataset from field data for canopy and background conditions. Autocorrelate veg signature across entire modeled BRDF. Use results to identify regions of viewing and solar angles ideal for identification (e. g. , spectral angle type classification). See if inverse of the model improves in these regions. 14

Research Timeline 15

Disseminating Results Primary Publications Proposed 16

Disseminating Results General Structure of Proposed Dissertation 17

Work so far… Literature search. Contacted and/or met with many researchers. Consulted and observed researchers doing field work. Spoke with government and other groups on marsh issues. Acquired marsh BRDF data and leaf optics and analyzed. Acquired several models and did initial experiments. Explored several coastal marshes by boat, SUV, and foot. Wrote proposal for special use permit of CBMNWRC. On science team for CBMNWRC; expected to file regular reports. Wrote proposal for CHRIS/Proba data. Spec. TIR Corp has agreed to shoulder IR&D costs for AISA flight. Got approval for radiometry instruments from GSFC. Have access to lab equipment for water analysis at GSFC. Got back-up and lab equipment at USDA. Borrowing a ASD handheld spectrometer. Attended data user workshop for MISR. 18

Analysis of Schill BRDF data for Spartina alterniflora data from Schill, TNC Work so far… 19 data from Ramsey and Rangoonwala, USGS

Work so far… NADIM Run Viewing Angle (º) Compiled and ran models NADIM SAIL MCRM SAIL-H RPV, MRPV Geo. SAIL 20 data from Ramsey and Rangoonwala, USGS

Work so far… Dr. Michael Kearney Dr. David Tilley Dr. Andy Rogers Dr. Fred Huemmrich, UMBC Dr. Victor Klemas, U of Del Dr. Richard Field, U of Del Dr. John Jensen, U of SC Dr. Betsy Middleton, NASA Dr. John Norman, U of Wisc Dr. Martha Anderson, USDA Dr. Charlie Walthall Dr. Andrew Baldwin, UMCP Dr. Narandra Goel Dr. Wenhan Qin Dr. Steven Unger, NASA Dr. Antonio Mannino, NASA Dr. Wayne Wright, NASA Dr. Amar Nayegandhi, USGS Dr. James Irons, NASA Dr. James Butler, NASA Adviser, discussions on research topic. Marsh field trip, April 2006 Discussions on marsh research, 2005 SAIL model, BRDF info Contacts on marsh research Talks & meeting on marsh field work Discussion, supported marsh RT model Field work experience and discussion Discussion on modeling canopy RT USDA contact, met and discussed work Info and advise on marsh work Discussed modeling canopies Hyperion project scientist Experience with CDOM measurements Discussed flyover of LIDAR Discussed radiometry and BRDF Discussed goniometers, toured facility 21

Work so far… Dr. Vern Vanderbilt, NASA Dr. Lawrence Corps, USDA Roger Stone, US FWS Dr. Dixie Birch, US FWS Dr. Glenn Carowan, US FWS Dr. Craig Daughtry, USDA Dr. Nancy Adamson, U of Md CE Leslie Hunter-Caro, Environmental Concern Penny Grealy, Environmental Concern Dr. David Nemerson, National Aquarium Dr. Lee. Anne Chandler, DNR Dr. Roman Jensien, MCBP Jay Charland, Assateague Coast Keeper Dr. Darlene Wells, DNR/MGS Dr. Fred Irani, DNR Dr. Court Stevenson, UMCES Dr. Steven Schill Dr. Amina Rangoonwala, USGS Dr. Elijah Ramsey III, USGS Dr. Oliver Weatherbee, Spec. TIR Corp. v Lengthy discussion on RT and RS. Radiometric field work CBMNWRC info, tour of Blackwater CBMNWRC info, handled proposal CBMNWRC info, proposal info Radiometric field work Contacts on growing S. alterniflora Info on growing S. alterniflora Contacts on critical areas Tour of two coastal bay marshes Tour of one coastal bay marsh Info on critical areas Info on RS work, contacts on field work Discussion on research topic S. alterniflora BRDF Data Optic data and papers Spec. TIR contact, info on AISA 22

Work so far… Dr. Francisco Artigas, MERI Dr. Martha Gilmore, Wesleyan U Dr. William Lawrence, BSU Dr. David Diner, NASA Milton Hom, NASA Amy Jacobs, Delaware DNR Dr. Ann Nolin, OSU Dr. Don Deering, NASA Dr. Dan Kimes, NASA Dr. V. Martins Dr. Ray Hunt, USDA Dr. Susan Ustin, UCD/CSTARS Dr. Mark Chopping, Montclair State U Kent Lawrenson, DCAir Photos Cassy Gurbisz, CBF Matt Mullin, CBF Kevin Boone, DNR David Hatchell, ASD Inc. Lawrence Ong, SSAI Georgiev, SSAI Discussed marsh spectra and instruments Discussed marsh classification & collab Contacts for instrument and data MISR proj scientist, PARABOLA III Advice and help with GSFC rad inst Info on marsh field work Discussion on marsh BRDF and RS Discussed measuring BRDF and DART Discussed instruments for BRDF Lengthy discussion on BRDF and RS Provided paper on sun glint work Lengthy discussion on BRDF field inst Info on flight cost, photos, etc. Info on KNMEC and Bishop’s Head Info on KNMEC Info on DNR mapping resources Info on ASD resources Contact for Hyperion data Tour and overview of GSFC goniometer 23

BACKUP SLIDES 24

Flow of Planned Research Tasks and Products Task Flow Diagram Research Products Generate Synthetic Data Characterization of canopy reflectance for marsh canopies Develop Model Collect Field Data Validate Model Characterization of canopy structure parameters Directional reflectance model for marshes Model inversion using ground truth Strategy for measuring canopy reflectance Optimize Geometry Validated of model for remote sensing Obtain and Process RS Data Closure Experiment Validation of optimized geometry Inversion of model using remote sensing data 25

Study Sites Blackwater Lake Crocheron Fishing Bay Bishops Head Marsh Maple Dam Road Hoopers Strait 26

Schneider et al. 2004 Kuusk 2004 http: //www. aai. ee/~andres/fieldwork. html 2006/12/05 Schill 2000 Walter-Shea, Mesarch 1998 http: //snrs. unl. edu/okarmcart/Addedphotos. html 2006/12/05 Kuusk 2004 http: //www. aai. ee/~andres/fieldwork. html 2006/12/05 27

Terminology of Radiometry Radiant Flux (Energy / time) (Joules / s or Watts) Radiance (Watts m-2 sr-1) Irradiance (Watts m-2) 28

Terminology of Radiometry Specular reflectance 29

Terminology of Radiometry Bidirectional Reflectance Distribution Function (BRDF) (sr-1) Bidirectional Reflectance Factor (BRF) 30

Terminology of Radiometry IMPORTANT PROPERTIES OF BRDF Inherent optical property: is independent of source or receiver. Instantaneous quantity: can only be approximated in the real world; usually by measuring BRF. Can vary with the wavelength of light, so spectra can change with geometry. BRDF is dependent on: § underlying structure of the reflecting medium, § optical properties of the medium’s constituents, § optical properties of the medium’s background. 31

Fresnel Reflectance and Transmittance 32

Marsh Canopy Radiative Transfer Model Sky Veg Air. Water I/F Under Water Bottom Sensor 33

BRDF Spectral Effects in Grass Backscattering Forward Scattering Sun behind viewer Sun in front of viewer Photos from Sandmeier et al. 1999 34