Digital Image Processing:A Remote Sensing PerspectiveFW5560Lt 13Lecture 13Vegetation TransformationsVegetation Spectral Characteristics and TheirCharacteristics and Their Impact on Transformations and IndicesVegetation reflectance is influence by the structure of ythe leaf and its pigmentationDifferent leaf pigmentsDifferent leaf pigments affect spectral signatureChl h ll d iChlorophyll dominant-greenCarotenoids (yellow/orange pigment)- 0.40 - 0.75 µm. Two types-xanthophyllsTwo types-xanthophylls and carotenes- absorb blue light. Protect the hl hllfcholorphyllfrom photodamage.Dominant Factors Controlling Leaf ReflectanceVegetation Indices- widely used transformation for 2 reasons:gyCertain aspects of the shape of spectral reflectance curves of different earth surface cover types can be enhanced byratioingdifferent earth surface cover types can be enhanced by ratioing.Undesirable effects on the recorded DNs such as variable ill i i d b i i i h b d dillumination caused by variations in topography can be reduced.From: Campbell-Introduction to Remote SensinggHealthy vegetation reflects strongly in the near-infrared portion of the spectrum while absorbing strongly in the visible red. Soil and water, show near equal reflectances in both the near-infrared and red portions.infrared and red portions.Thus, a ratio image of Landsat ETM+ Band 4 (Near-Infrared - 0.8 to 1 1 mm) divided by Band 3 (Red06to07mm)wouldresultto 1.1 mm) divided by Band 3 (Red -0.6 to 0.7 mm) would result in ratios much greater than 1.0 for vegetation, and ratios around 1.0 for soil and water. The discrimination of vegetation from other surface cover types is significantlyenhanced. Better able to identify areas ofunhealthy or stressed vegetation, whichunhealthy or stressed vegetation, whichshow low near-infrared reflectance, asthe ratios would be lower than forhealthy green vegetationhealthy green vegetation.Reflectance Response of a Single Magnolia Leaf (Mlidifl)t D dR l ti Wt C t t(Magnolia grandiflora) to Decreased Relative Water ContentInfrared/Red Ratio Vegetation IndexInfrared/Red Ratio Vegetation IndexThe near-infrared (NIR) to redThe nearinfrared (NIR) to redsimple ratio (SR) is the firsttrue vegetation index:SR=NIRredIt takes advantage of the inverserelationship between chlorophyllredppyabsorption of red radiant energyand increased reflectance of nearinfrared energy for healthynear-infrared energy for healthyplant canopies (Cohen, 1991) .NlidDiff VttiIdNormalized Difference Vegetation IndexThe generic normalized difference vegetation index (NDVI):The generic normalized difference vegetation index (NDVI):NIR−redNDVI=NIRredNIR+redhas provided a method of estimating net primary production over varying biome types (e.g.Lenneyet al., 1996), identifyingvarying biome types (e.g. Lenneyet al., 1996), identifying ecoregions (Ramsey et al., 1995), monitoring phenologicalpatterns of the earth’s vegetative surface, and of assessing the length of the growing season and drydown periods (Hueteandlength of the growing season and dry-down periods (Hueteand Liu, 1994).Using and Ecoregion Framework to Analyze Land Cover and Land Use Dynamics, Gallant et al, 2004, Environmental ManagementPerpendicularPerpendicular Vegetation IndexSilLi PVI 0Soil Line PVI = 0Water PVI < 0Vegetation PVI > 0PVI measures the orthogonal distance fthilifrom the pixel in question to the soil line.Evaluation Of Landsat-5 Thematic Mapper Data For Detecting Potential Construction Aifiihlld d i1990Areas For Intensified Housing, Thomas J. Blaser, Ronald J.P. Lyon and Kai Lanz1990, Geoscience and Remote Sensing Symposium, 1990. IGARSS '90. 'Remote Sensing Science for the Nineties, 10th Annual InternationalPhenological Cycles of San Joaquin and Imperial Valley California CropsValley, California Crops and LandsatMultispectral Scanner IfOFildImages of One Field During A Growing SeasonDistribution of Pixels in a Scene in Red and Near-infrared Multispectral Feature Space ppKauth-Thomas “Tasseled Cap”