clasificaciones y análisis de mezclas espectrales · el problema . después. de casi 40 años de...
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Clasificaciones y Análisis de Mezclas Espectrales
Clasificaciones y Análisis de Mezclas Espectrales
Ejercicios para hoy
1. Correcciones atmosféricas 2. Análisis de Componentes Principales (PCA) y la
Transformación de la Fracción de Ruido Mínimo (MNF Transform)
3. Clasificación no supervisada 4. Conversión de raster a vector 5. Colección de muestras 6. Clasificación supervisada 7. Despliegue en N dimensiones 8. Análisis de mezclas espectrales (SMA) 9. Filtración de los resultados
Cobertura de la tierra - 2008*
*Para validar
¿Porque necesitamos hacer clasificaciones?
El problema
Después de casi 40 años de percepción remota ambiental desde el lanzamiento de Landsat-1 en el 23 de julio de 1972, todavía existe el problema de identificar cobertura de la tierra (delineación e cuantificación) fácilmente y con exactitud
False color LandSat TM mosaic courtesy of NASA / USGS
Belize City
Source: TBD
Simulated true color LandSat TM image courtesy of NASA / USGS; image captured 28 March 2000
Simulated false color LandSat TM image courtesy of NASA / USGS; image captured 28 March 2000
Aerial photo of interface between savanna and forest near Belize City, April 5, 2009
No.Date -
Ground Condition
Date - Publication
Original Source
Published as Imagery Used Resolution Geographic coverage, original
Number of Classes
1c. 1990, c.
20002005 Earth
Satellite Corporation
GeoCover LC 1990
Landsat TM, Landsat ETM+ 30m global 11
2 1992-93 USGS GLCC AVHRR 1km global 96
3
1992-93 1998
PROARCA / CAPAS
"Central American
Vegetation/Land Cover
Classification and
Conservation Status"
AVHRR 1km regional 25
4
1991-99 2002
World Bank
"Central America
Ecosystems Mapping Project"
Landsat TM 30m regional 196
5 2000 2002 JRC GLC 2000 SPOT Vegetation 1km global 23
62000, 2001, 2002, 2003, 2004, 2005
2008 UMD / NASA MOD44B MODIS 500m global N / A
7 2000, 2003, 2004, 2005
2006 U. Ark. / SERVIR
SERVIR MesoClass MODIS 500m regional 6
8 2005 2005 USGS MODIS 500m regional 9
92004-06 2008 ESA /
MEDIAS France
GlobCover project MERIS 300m global 24*
10 2000, 2005, 2007, 2008
2008 ESA / GeoVille
DIVERSITY project MERIS* 300m regional 12
Mosaico temporal de imágenes de 2009, con menos que 2% de
nubosidad
Source: p. 2-25, GOFC-GOLD REDD Sourcebook, Nov. 2009 edition
Source: Goodenough et al (2002): “Report on the Evaluation and Validation of EO-1 for Sustainable Development (EVEOSD) Project”
Radiometric calibration
Atmospheric correction Dark object subtraction
Intra-scene calibration Histogram matching
Mosaic, as necessary
Image Processing: Corrections
Preferably in ENVI
In ERDAS
In ERDAS
In ERDAS
El sistema ideal de percepción remota (1) Fuente uniforme de
energía
(4) Súper sensor
(2) Atmosfera sin interferencia
(3) Interacciones únicas con el superficie de la tierra
Fuente: M. Vasquez (2006)
Interacciones de Energía con la Atmosfera
Scattering Refracción Absorción
Fuente: B. Howell (2006)
Energía en el Objeto
Radiacion Incidente puede ser… • Reflejada • Transmitida • Absuelto (y reEmitida)
I = R + T + A
Fuente: B. Howell (2006)
Usos de Percepción Remota
• Actualizar o reemplazar mapas existentes
• Determinar áreas de categorías conocidas
• Hacer inventarios de tipos de cobertura
• Documentar cambios entre periodos
• Medir condiciones en una área
• Medidas cuantitativa de propiedades
Fuente: B. Howell (2006)
Centroamérica: 50 imágenes cubren
50 millón de ha, =25 GB de datos para procesar
Entonces, desde L4 en 1984 hasta al presente, hay ~769 escenas disponible para cualquier área (23 imágenes por año por L5 y L7)
Senderos de LandSat para Centroamérica
Los senderos fijos en el sistemas de referencia de Landsat
Resultados de una búsqueda en Glovis para El Salvador – 262 imágenes con menos de 30% de nubosidad, entre enero de 2007 y febrero de 2009
Landsat TM False color mosaic 28-03-2000
Land cover map 2004
Landsat TM False color mosaic 28-03-2000
Land cover map 2004 (Source: BTFS)
Landsat TM False color mosaic 28-03-2000
Land cover map 2004 (Source: BTFS)
1. Green is forest
2. To be able to extract the green is to be able to extract the forest cover
Identifying Forest Cover w/ Satellite Imagery
Landsat TM False color mosaic 28-03-2000
Forest cover map 2004 (Source: BTFS)
•El Sistema de Sistemas de la Observación de la Tierra (GEOSS)
•La Carta Internacional sobre el Espacio y Grandes Catástrofes
•El Sistema de Información Ambiental Mesoamericano (SIAM)
El Sistema de Visualización y Monitoreo (SERVIR)
Terra Terra Aqua
Test-bed at NASA MSFC
Environmental Monitoring & Decision
Support Products
Web Interface www.servir.net
LandSat MODIS SRTM AMSR-E IKONOS ASTER
Mesoamerica’s Earth Observation & Forecasting Platform
Fires
Red Tides
Land Cover / Use Change
Data ingest from EOS and Central EDOS EDOS
Operational Node at CATHALAC Panama
Agriculture Biodiversity Climate Ecosystems Energy Disasters Health Water Weather
Thematic Areas
Central American Government agencies NGOs, researchers Educators, etc.
Users
Impacts Emergency Response Policy Changes Corridor Preservation Species Preservation Sustained Development Improved livelihoods
SERVIR tiene herramientas muy relevantes al tema de monitoreo de REDD
SERVIR Disaster Response (2004-) 1. Red tide event - El Salvador (June 2004)
2. Flooding – Panama City, Panama (Sept. 2004)
3. Flooding - Rio Sixaola, Costa Rica / Panama (Jan 2005)
4. Hurricane Stan – Guatemala, Mexico, El Salvador (Oct .2005)
5. Flooding – Colon Province, Panama (Nov. 2006)
6. Fire - Mountain Pine Ridge Forest Reserve, Belize (May 2007)
7. Hurricane Dean – Mexico / Belize (Aug. 2007)
8. Hurricane Felix – Nicaragua / Honduras (Sept. 2007)
9. Tropical Storm Noel – Dominican Republic (Oct. 2007)
10. Tropical Storm Olga – Dominican Republic (Dec. 2007)
11. Turrialba Volcano – Costa Rica (April 2008)
12. Tropical Storm Arthur – Belize (June 2008)
13. Hurricane Gustav – Haiti / Dominican Rep. (August 2008)
14. Hurricane Hanna – Haiti (Sept. 2008)
15. Hurricane Ike – Haiti (Sept. 2008)
16. Landslide – Huahua Michoacán, Mexico (Oct. 2008)
17. Tropical Depression 16 – Belize / Guatemala / Honduras (Oct. 2008)
18. Flooding – Costa Rica / Panama (Nov. 2008)
19. Landslide – Alta Verapaz, Guatemala (Jan. 2009)
20. Earthquake – San Jose metropolitan area, Costa Rica (Jan. 2009)
21. Fire – Volcan Santo Tomas, Quetzaltenango, Guatemala (Feb. 2009)
22. Flooding – Lago Enriquillo, Dominican Republic (Feb. 2009)
Extracción de Objetos • Clasificación
• Índices / ratios
• Umbrales de bandas
(“band thresholding”)
• Análisis de mezclas espectrales
• Supervisada • No supervisada • NDVI • NBR / NDBR
• Varios – Sombra, Suelo, Vegetación; Sombra, Suelo, Vegetación verde, vegetación no fotosintética
Pasos básicos en clasificación de imágenes: 1) Estudio y organización de los datos 2) Aplicación de un algoritmo de clasificación 3) Validación
Estudio y organización de los datos
Estudio ¿Que esta en la escena / imagen? ¿ Cuales bandas están disponible? ¿ Cuales preguntas necesitan respuestas? ¿ Se puede responder a las preguntas con la imagen? ¿ Hay suficiente información para distinguir que esta en la escena? Organización de los datos ¿ Cuantas clusters se puede re-organizar en espacio n? ¿ Como son los limites de los clusters? ¿ Los clusters corresponde a los clases deseados?
Clasificación
Clasificación es el proceso de asignar los pixeles a clases homogéneos basado en análisis de las estadísticas de valores de reflectancia en uno o mas bandas.
Clasificación es el proceso de derivar information clases informativos / utiles de clases espectrales.
Se nombran los procesos de clasificación como supervisada o no supervisada basado en la metodología para “entrenar” el classifier (clasificador?).
Con datos de ‘entrenamiento,’ los dos sistemas utilicen la misma forma de operación (división basada en las estadísticas).
Fuente: B. Howell (2006)
Clasificación
The Attainment of the Sanc Grael Dante Gabriel Rosetti
Pros: • Puede apoyar en la descripción de usos y cobertura de la tierra
• Puede simplificar el proceso de detección de cambios
• Con procesamiento posterior, puede generar polígonos con atributos para uso en un SIG
Contra: • Clasificación con ella misma, no va extraer información útil de la data
• No hay clasificadores universales
• NO es perfecto
• Necesita procesamiento posterior para llegar a una foto bonita
Fuente: B. Howell (2006)
Histogramas de cada banda
Fuente: B. Howell (2006)
Respuestas espectrales
Fuente: B. Howell (2006)
Histogramas de cada banda
ASTER: Advanced Spaceborne Thermal Emission & Reflection Radiometer
Terra
One of 5 sensors on the satellite Terra (launched in Dec. 1999); ‘on-call’
Similar to the Thematic Mapper sensor on the LandSat satellites
Swath about 1/9 the size of LandSat swath
14 bands (3 15m / 6 30m / 5 90m) measuring light from the visible to infrared thermal wavelengths
Uno de los 5 sensores en el satélite Terra (lanzando en Dic. de 1999); debe estar encendido
Similar que el sensor ‘Thematic Mapper’ de LandSat Tamaño de una escena es 1/9 de una escena de LandSat 14 bandas (3 de 15m / 6 de 30m / 5 de 90m) midiendo
luz en longitudes de onda visible a infrarrojo termal
Respuestas espectrales
Fuente: B. Howell (2006)
Histogramas de cada banda
Firmas espectrales de materiales comunes
Absorción de clorofila
Dispersión en las celdas
Absorción de agua
Firmas espectrales
Fuente: B. Howell (2006)
Clasificación No Supervisada
False color LandSat TM mosaic courtesy of NASA / USGS
Belize City
14-Nov-1980
Belize City pop’n ~39,771
False color LandSat MSS image courtesy of NASA / USGS
Ladyville area
Belize’s International Airport
Population data from Belize CSO
27-Dec-1989
Savanna clearing for shrimp farm development
Diminishing mangrove forests
Coastal development (Buttonwood Bay & Bella Vista)
False color LandSat TM image courtesy of NASA / USGS Population data from Belize CSO
28-Mar-2000 Expansive shrimp ponds
Settlement on former mangrove forest (Vista del Mar)
Coastal development
New beachfront properties
Expansion of south-side Belize City
Cleared mangrove
Expansion of north-side Belize City (Belama)
False color LandSat TM image courtesy of NASA / USGS Population data from Belize CSO
12-Feb-2004 Nova Shrimp Farm at size of Belize City
Clearing of 100s of acres of mangrove for Port development
Land reclamation at the Marine Parade
False color LandSat ETM image courtesy of NASA / USGS Population data from Belize CSO
31-March-2007 Nova Shrimp Farm ceases operations
Further wetland clearing at Belama Phase IV
False color ASTER image courtesy of NASA / JAXA Population data produced by extrapolating Belize CSO data
1980 1989 1998
2000 2002 2006
La Ciudad de Belice: 1980 hasta 2006
27-Dec-1989
False color LandSat TM image courtesy of NASA / USGS Population data interpolated from Belize CSO data
Belize City pop’n ~42,518
27-Dec-1989
False color LandSat TM image courtesy of NASA / USGS Population data interpolated from Belize CSO data
Belize City pop’n ~42,518
Approx. area: 2,089 acres (845 ha.)
2-Feb-2006
False color ASTER image courtesy of NASA / JAXA Population data extrapolated from Belize CSO data
Belize City pop’n ~64,700
2-Feb-2006
False color ASTER image courtesy of NASA / JAXA Population data extrapolated from Belize CSO data
Belize City pop’n ~64,700
Approx. area: 3,382 acres (1,369 ha.)
Antes: Belize City en 1980 • ~39,771 habitantes • 1,706 acres (6.9 km2) • Densidad de 5,756 personas / km2
• Densidad nacional de 6 personas / km2 Reciente: Belize City en 2007 • ~66,422 habitantes • 3,449 acres (14 km2) • Densidad de 4,758 personas / km2
• Densidad nacional de 13 personas / km2
• El área ha doblado entre 1980 y 2007 • El crecimiento anual era ~106 acres / 43 ha. • La mayoría de la expansión de 705 ha fue
deforestación de manglares y destrucción de humedales
False color ASTER image courtesy of NASA / JAXA
0
500
1,000
1,500
2,000
2,500
3,000
3,500
4,000
31-Mar-072-Feb-0619-Sep-0228-Mar-0015-Sep-9827-Dec-8914-Nov-80
Date
Area (
acres)
0
10,000
20,000
30,000
40,000
50,000
60,000
70,000
Pop
ula
tion
Area Population
Tendencias del crecimiento de la población y expansión urbana en la Ciudad de Belice
0
20
40
60
80
100
120
140
160
180
1981 1990 1999 2000 2003 2006
Tendencias de expansión urbana (cambios anuales)
383 acres cortadas
654 acres cortadas
143 acres cortadas
448 acres cortadas
48 acres cortadas / reclamadas
67 acres cortadas / reclamadas
Annu
al e
xpan
sion
rate
(acr
es /
yr)
Expansión de 705 ha entre nov de 1980 y marzo de 2007
Rates of Urban Expansion & Population Density Date Area Pop’n Pop’n
Density (people / km2)
Change From
previous period (acres)
Avg. change per year from
Previous period (acres)
Period of
Change
Major Drivers of Land Cover Conversion in Period Acres Ha. Km2
Mar-07 3,449 1,396 13.96 66,422 4,758 67 57.3 2006- 2007
Belama Phase IV
Feb-06 3,382 1,369 13.69 64,128 4,684 48 13.7 2002- 2006
Land reclamation
Sep-02 3,334 1,349 13.49 56,700 4,203 448 179.2 2000- 2002
Development of Port
Mar-00 2,886 1,168 11.68 49,050 4,199 143 95.3 1998- 2000
General expansion
Sep-98 2,743 1,110 11.10 47,947 4,320 654 72.7 1989- 1998
Belama Phases I-III
Dec-89 2,089 845 8.45 42,518 5,032 383 42.6 1980- 1989
Buttonwood Bay, general expansion
Nov-80 1,706 691 6.91 39,771 5,756 N / A N / A N / A N / A
Aerial photo by Emil A. Cherrington
Unsupervised Classification
Basic Iterative Clustering Algorithm (K-Means) • Place K points into the feature space containing the
samples to be clustered. These points represent initial group centroids.
• Assign each sample to the group that has the
closest centroid. • When all samples have been assigned, recalculate
the positions of the K centroids. • Repeat Steps 2 and 3 until the centroids no longer
move.
Fuente: B. Howell (2006)
Unsupervised Classification
Basic Iterative Clustering Algorithm (K-Means) • Place K points into the feature space containing the
samples to be clustered. These points represent initial group centroids.
• Assign each sample to the group that has the
closest centroid. • When all samples have been assigned, recalculate
the positions of the K centroids. • Repeat Steps 2 and 3 until the centroids no longer
move.
Fuente: B. Howell (2006)
Unsupervised Classification
Basic Iterative Clustering Algorithm (K-Means) • Place K points into the feature space containing the
samples to be clustered. These points represent initial group centroids.
• Assign each sample to the group that has the
closest centroid. • When all samples have been assigned, recalculate
the positions of the K centroids. • Repeat Steps 2 and 3 until the centroids no longer
move.
Fuente: B. Howell (2006)
Unsupervised Classification
Basic Iterative Clustering Algorithm (K-Means) • Place K points into the feature space containing the
samples to be clustered. These points represent initial group centroids.
• Assign each sample to the group that has the
closest centroid. • When all samples have been assigned, recalculate
the positions of the K centroids. • Repeat Steps 2 and 3 until the centroids no longer
move.
Fuente: B. Howell (2006)
Unsupervised Classification
Improving clustering • “Real world” sample
distributions are much more likely to be irregularly shaped with cluster axes rotated to each other.
• These distributions are better
characterized by parametric statistics.
• Simple n-dimensional space
segregation is more likely to assign pixels to incorrect clusters.
Fuente: B. Howell (2006)
Unsupervised Classification
Improving clustering • “Real world” sample
distributions are much more likely to be irregularly shaped with cluster axes rotated to each other.
• These distributions are better
characterized by parametric statistics.
• Simple n-dimensional space
segregation is more likely to assign pixels to incorrect clusters.
Fuente: B. Howell (2006)
Unsupervised Classification
Improving clustering • “Real world” sample
distributions are much more likely to be irregularly shaped with cluster axes rotated to each other.
• These distributions are better
characterized by parametric statistics.
• Simple n-dimensional space
segregation is more likely to assign pixels to incorrect clusters.
Fuente: B. Howell (2006)
Unsupervised Classification
ISODATA (Iterative Self-Organizing Data Analysis Technique) • Operates in the same iterative fashion as K-Means
with three significant differences… • Uses parametric statistics to describe clusters and
determine nearest centroids • New clusters can formed by splitting “elongated”
clusters into multiples
• Clusters with centroids that are “too close” can be lumped together
• Because of these differences, K becomes a
“desired” number of final classes, not an absolute
Fuente: B. Howell (2006)
Unsupervised Classification
ISODATA (Iterative Self-Organizing Data Analysis Technique) • Operates in the same iterative fashion as K-Means
with three significant differences… • Uses parametric statistics to describe clusters and
determine nearest centroids • New clusters can formed by splitting “elongated”
clusters into multiples
• Clusters with centroids that are “too close” can be lumped together
• Because of these differences, K becomes a
“desired” number of final classes, not an absolute
Fuente: B. Howell (2006)
Unsupervised Classification
ISODATA (Iterative Self-Organizing Data Analysis Technique) • Operates in the same iterative fashion as K-Means
with three significant differences… • Uses parametric statistics to describe clusters and
determine nearest centroids • New clusters can be formed by splitting “elongated”
clusters into multiples
• Clusters with centroids that are “too close” can be lumped together
• Because of these differences, K becomes a
“desired” number of final classes, not an absolute
Fuente: B. Howell (2006)
Unsupervised Classification
ISODATA (Iterative Self-Organizing Data Analysis Technique) • Operates in the same iterative fashion as K-Means
with three significant differences… • Uses parametric statistics to describe clusters and
determine nearest centroids • New clusters can formed by splitting “elongated”
clusters into multiples
• Clusters with centroids that are “too close” can be lumped together
• Because of these differences, K becomes a
“desired” number of final classes, not an absolute
Fuente: B. Howell (2006)
Unsupervised Classification
ISODATA (Iterative Self-Organizing Data Analysis Technique) • Operates in the same iterative fashion as K-Means
with three significant differences… • Uses parametric statistics to describe clusters and
determine nearest centroids • New clusters can formed by splitting “elongated”
clusters into multiples
• Clusters with centroids that are “too close” can be lumped together
• Because of these differences, K becomes a
“desired” number of final classes, not an absolute
Fuente: B. Howell (2006)
a) ISODATA initial distribution of five hypothetical mean vectors using ±1σ standard deviations in both bands as beginning and ending points. b) In the first iteration, each candidate pixel is compared to each cluster mean and assigned to the cluster whose mean is closest in Euclidean distance. c) During the second iteration, a new mean is calculated for each cluster based on the actual spectral locations of the pixels assigned to each cluster, instead of the initial arbitrary calculation. This involves analysis of several parameters to merge or split clusters. After the new cluster mean vectors are selected, every pixel in the scene is assigned to one of the new clusters. d) This split–merge–assign process continues until there is little change in class assignment between iterations (the T threshold is reached) or the maximum number of iterations is reached (M).
Jensen, 2005
a) Distribution of 20 ISODATA mean vectors after just one iteration using Landsat TM band 3 and 4 data of Charleston, SC. Notice that the initial mean vectors are distributed along a diagonal in two-dimensional feature space according to the ±2σ standard deviation logic discussed. b) Distribution of 20 ISODATA mean vectors after 20 iterations. The bulk of the important feature space (the gray background) is partitioned rather well after just 20 iterations.
Jensen, 2005
Jensen, 2005
Plot of the Charleston, SC, Landsat TM training statistics for five classes measured in bands 4 and 5 displayed as cospectral parallelepipeds. The upper and lower limit of each parallelepiped is ±1σ. The parallelepipeds are superimposed on a feature space plot of bands 4 and 5.
Jensen, 2005
ISODATA Clustering
Logic
Jensen, 2005
Classification Based on ISODATA Clustering
Jensen, 2005
Clasificación Supervisada
Clasificación supervisada
1) estimación de similitud espectral 2) asociación de tipos espectrales con clases útiles SUPOSICION BASICO Objetos de interés tienen “firmas espectrales” claros *Esto no siempre es el caso A veces hay que modificar la data para que sea real - combinaciones de bandas - imágenes multi-temporales
Clases, áreas de muestras, y mímicos
Clase: Unido deseado, en la forma de un cluster espectral 2 atributos: identidad y firma espectral Área de muestra: una región de una imagen que es un buen ejemplo de un clase; se utilice para definir clústeres espectrales de una clase especifica; se define la identidad con foto-interpretación o información del campo Mímicos: otros unidos de mapeo con clústeres similares
Clasificación supervisada
Supervised classification involves imposing a priori information classes on a landscape.
Implicit in the supervised classification process is the notion that the spectral data of members of a class will have similar statistical characteristics and that those characteristics can be visually discerned and manually segregated by a human.
The process of creating a class structure and determining the statistical characteristics of each class is called training.
Training is the method by which a classifier “learns” the appearance of individual classes.
For the classifier to be successful in properly assigning pixels to a class, the training samples must be “pure” (consisting of class members only).
Fuente: B. Howell (2006)
Clasificación supervisada
• Filosofía y estrategia de entrenamiento manual
• Seleccionar las bandas insumos con mayor información
• Mostrar combinaciones de bandas con mayor contraste entre clases
• No seleccionar muestras que no son miembros del clase de interés
• Examinar histogramas para determinar si las muestras son buenas (separables)
• Seleccionar un rango de muestras de un clase, y combinarlos antes de la clasificación
Fuente: B. Howell (2006)
Parallelepiped
Hybrid
Minimum Distance
Maximum Likelihood
Classifiers
Parallelepiped • Determines class membership using parallelepipeds (n-dimensional “boxes” in feature space)
• Advantages:
• Very fast
• Can classify 100% of candidates
• Makes good-looking output
• Disadvantages:
• Candidates that fall outside any parallelepiped remain unclassified
• Candidates that fall in overlaps are assigned to the “first” parallelepiped
• Poorly matched to normal data distributions
Fuente: B. Howell (2006)
Classifiers
Minimum Distance • Determines class membership by measuring distance from class centroid
• Advantages:
• Fast
• More accurate* classification than Parallelepiped
• Better than Parallelepiped for handling “real world” data distributions
• Disadvantages:
• Candidates that fall outside distance limits remain unclassified
• Candidates that fall in overlaps are assigned by an operator defined rule
• Imperfectly matched to normal data distributions
*assuming you know how to make it so
Fuente: B. Howell (2006)
Classifiers
Maximum Likelihood • Determines class membership using parametric statistics
• Advantages:
• Very well matched to normal data distributions
• More accurate classification* than Parallelepiped or Minimum Distance
• Candidates that fall into overlaps are assigned based on likelihood of membership
• Disadvantages:
• Candidates that fall outside any parallelepiped remain unclassified
• Accuracy heavily dependent on normal data distributions
*assuming you know how to make it so
Fuente: B. Howell (2006)
Classifiers
Hybrid • Determines class membership using parametric and nonparametric techniques
• Advantages:
• Fast and very accurate*
• Perform first-order classifications using Parallelepipeds
• Perform second-order classification on outliers and overlaps using distance or likelihood rule
• Disadvantages:
• Virtually every mistake that can be made using Parallelepiped, Minimum Distance, and Maximum Likelihood classifiers can be achieved in a single operation
*assuming you know how to make it so
Fuente: B. Howell (2006)
Análisis de Mezclas Espectrales
•Imágenes multiespectrales miden spectra integrada en cada píxel
•Cada píxel contiene materiales diferentes, cada con su firma espectral diferente
•Varios tipos de spectra usualmente están mezclados. Esos son mezclas.
•Otros tipos no mezcla mucho.
Fuente: A. Gillespie, la Universidad de Washington
Usualmente, el numero de clases (‘endmembers’) útiles para datos de Landsat es 4-5 Puede ser 8-10 para datos híper-espectrales Hay muchos componentes espectrales en varias escenas, pero usualmente no mezclan, entonces no son útiles.
Análisis de mezclas espectrales es útil porque –
1) Genera imágenes de fracciones que
se puede entender fácilmente
2) Reducción en la dimensionalidad de los datos sin botar mucha información útil
3) Identificación de efectos topográficos para mas estable información para análisis en SIG
Soil Soil
1 0 0
9 0
8 0
7 0
6 0
5 0
4 0
3 0
2 0
1 0
1 0 0 9 0 8 0 7 0 6 0 5 0 4 0 3 0 2 0 1 0
1 0 0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
% suelo Suelo
Sombra
Vegetación verde
Fuente: UW ESS 421 (2004)
Fuente: Lu et al (2002)
SMA can easily extract areas of
bare soil
CATHALAC (unpublished, Nov 2009)
Interpreting spectral unmixing results
Color Code
Color in RG comp % Soil
% Photosynthetic Vegetation Description
1 Yellow Very high (90-100%)
Very high (90-100%) Cropland
2 Light green
Low-Very Low (0-30%)
High (80-100%) Open forest
3 Light green
Medium (60-70%)
Medium (40-50%) Shrubland
4 Dark green
Very low (0-10%)
Medium (40-80%) Closed forest
5 Red Very high (90-100%)
Low (10-20%) Bare land / urban
6 Coffee brown
Low (10-30%)
Low-Medium (30-50%) Mangrove scrub
7 Black Very low (0-10%)
Low-Very Low (0-20%) Water
Black Very low (0-10%)
Low-Medium (20-40%) Wetland
CATHALAC (unpublished, Nov 2009)
Interpreting spectral unmixing results
Color Code
Color in RG comp % Soil
% Photosynthetic Vegetation Description
1 Yellow Very high (90-100%)
Very high (90-100%) Cropland
2 Light green
Low-Very Low (0-30%)
High (80-100%) Open forest
3 Light green
Medium (60-70%)
Medium (40-50%) Shrubland
4 Dark green
Very low (0-10%)
Medium (40-80%) Closed forest
5 Red Very high (90-100%)
Low (10-20%) Bare land / urban
6 Coffee brown
Low (10-30%)
Low-Medium (30-50%) Mangrove scrub
7 Black Very low (0-10%)
Low-Very Low (0-20%) Water
Black Very low (0-10%)
Low-Medium (20-40%) Wetland
Source: ITTO / JOFCA
2. Low vegetation (e.g. cropland, shrubland): Should be defined by high chlorophyll content and some soil exposure b/c of usual low plant density (i.e. no canopy)
4. Closed tree canopy (e.g. ‘mature’ forest): Should be defined principally by low soil exposure and moderate to high chlorophyll content
1. Bare land (e.g. urban areas): Should be defined by high soil exposure and no chlorophyll content
3. Open tree canopy (e.g. ‘open’ forest): Should be defined principally by some soil exposure and high chlorophyll content
1. 2. 3. 4.
Spectral Mixture Analysis works with spectra that mix together to estimate mixing fractions for each pixel in a scene.
Spectral Mixtures, green leaves and soil
0
20
40
60
80
100
0 1 2 3
Wavelength, micrometers
Ref
lect
ivity
, %
0% leaves25% leaves50% leaves75% leaves100% leaves
The extreme spectra that mix and that correspond to scene components are called spectral endmembers.
Please note – wavelength scale is messed up Source: TBD
In a forest, important endmembers may be leaves, wood, shade, and soil.
In a desert, leaves may be less important, but there may several rock types.
Forest Spectral Endmembers
0
20
40
60
80
100
0 1 2 3
Wavelength, micrometers
Ref
lect
ivity
, %
dry grassleavessoil
Endmembers from one type of scene – forest, lake, desert – form a cohort.
Source: TBD
1: Unconstrained All MNF components
2: Constrained – Weight 1 All MNF components
3: Constrained – Weight All MNF components
Round 1: 1st set of samples, selected from PPI of all MNF components
4: Constrained – Weight 50 All MNF components
5: Unconstrained ALI bands 3,4,5,6,8,9
6: Constrained – Weight ALI bands 3,4,5,6,8,9
Round 1: 1st set of samples, selected from PPI of all MNF components
7: Constrained – Weight 1 ALI bands 4,5,6,8
8: Constrained – Weight 1,000 ALI bands 4,5,6,8
9: Constrained – Weight MNF components 1,2,3
Round 2: 2nd set of samples, selected from PPI of first 3 components
10: Constrained – Weight 1 MNF components 1,3
11: Constrained – Weight 100 MNF components 1,3
12: Constrained – Weight MNF components 1,3
Round 2: 2nd set of samples, selected from PPI of first 3 components
13: Unconstrained MNF components 1,3
14: Constrained – Weight 1 All MNF components
15: Constrained – Weight
Round 2: 2nd set of samples, selected from PPI of first 3 components
Color 2000 2005 2010Black Low Low LowRed High Low LowGreen Low High LowBlue Low Low HighYellow High High LowMagenta High Low HighCyan Low High HighWhite High High High
RGB NDVI composite: 2000-2005-2010
Cambio de cobertura: 2000-2010
Color 2000 2005 2010Black High High High Red Low High High Green High Low High Blue High High Low Yellow Low Low High Magenta Low High Low Cyan High Low Low White Low Low Low
Cambio de cobertura: 2000-2010
Color KeyBlack No change: forestRed Regenerated 2000-05; no change 2005-10Green Cut 2000-05, regenerated 2005-10Blue No change 2000-05; cut 2005-10Yellow No change 2000-05; regeneration 2005-10Magenta Regenerated 2000-05, re-cut 2005-10Cyan Cut 2000-05; no change 2005-10White No change: non-forest
Índices
NDx
ND
y
A
B
° x
NDx
ND
y
Sombra
° x
A con sol
B con sol
NDx
ND
y
A
B
° x
NDx
ND
y
Sombra
° x
A con sol
B con sol
Línea de ratio constante
y
x
x/y
y/z
A
B
Después: LandSat7 - 11 de mayo de 2007
Plumas de humo
Cicatrices
Antes: LandSat7 - 21 de marzo de 2006
2006
2007
Procesamiento Digital
Principio: Se puede aplicar metodologías para extraer info útil de imágenes satelitales
Normalized Difference Vegetation Index (NDVI): ratio entre la luz infrarrojo cercano (NIR) y rojo (R), indicando vegetación en estrés
Normalized Burn Ratio (NBR): ratio entre infrarrojo medio (SWIR) y infrarrojo cercano (NIR), para delinear cicatrices (muy similar a NDVI)
LandSat: 21 March 2006
LandSat: 11 May 2007
Contamination por el humo
Differencing 2007 NDVI against 2006 NDVI
LandSat: 21 March 2006
LandSat: 11 May 2007
Differencing 2007 NBR against 2006 NBR
2006
NDBR NDVI Diff.
2007
LandSat7: 11 de mayo de 2007
Estimación: ~24,000 acres quemadas
Validación
c. 2000
c. 2009
Matrices de confusion / Matrices de error
Datos de validación A B C D E F
A
B
C D
E F D
atos
de
la c
clas
ifica
ción
Sumas de columnas
Sumas de filas
480 0 5 0 0 0 485
0
0
0
0
0
0
0
0
480
52
16
68
0 20 0 0 72
Class
mangroves no mangroves water Total
User accuracy
Producer accuracy
Total class accuracy
Number %
mangroves 1 59 10 70 21% 1% 50% 26%
no mangroves 1 75 5 81 24% 93% 55% 74%
water 0 2 186 188 55% 99% 93% 96%
Total 2 136 201 339 100%
Producer Accuracy 50% 55% 93% 77.3%
Class
mangroves no mangroves water Total
User accuracy
Producer accuracy
Total class accuracy
Number %
mangroves 2 77 6 85 26% 2% 100% 51%
no mangroves 0 54 5 59 18% 92% 39% 65%
water 0 7 182 189 57% 96% 94% 95%
Total 2 138 193 333 100
%
Producer Accuracy 100% 39% 94% 71.5%
Fuentes de Mayor Información Libros (vea www.amazon.com) - • Teledetección Ambiental (2002) – Emilio Chuvieco • Remote Sensing and Image Interpretation (2007) – Thomas
Lillesand, Ralph Kiefer, Jonathan Chipman • Remote Sensing of the Environment (2006) – John R.
Jensen • Remote Sensing for GIS Managers (2005) – Stan Aronoff En línea - • TELEDET: http://www.teledet.com.uy/tutorial-imagenes-
satelitales/imagenes-satelitales-tutorial.htm • NASA: http://rst.gsfc.nasa.gov/ • CATHALAC: [email protected] • GOOGLE / Wikipedia
Referencias / Reconocimientos
Mucha de la información en este presentación fue adoptada de los siguientes fuentes:
• Burgess Howell, NASA GSFC (2006) • Jason Tullis, University of Arkansas (2005) • Lecturas / materiales del curso ESS 421 y ESS
422 de la U. de Washington (2004)
¿Preguntas?