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Transcript of IGARSS 2011.ppt
Archaeological Land Use Characterization Archaeological Land Use Characterization using Multispectral Remote Sensing Datausing Multispectral Remote Sensing Data
Dr. Iván Esteban Villalón Turrubiates, Dr. Iván Esteban Villalón Turrubiates, Member,Member, IEEE IEEE María de Jesús Llovera TorresMaría de Jesús Llovera Torres
UNIVERSIDAD DE GUADALAJARAUNIVERSIDAD DE GUADALAJARACENTRO UNIVERSITARIO DE LOS VALLESCENTRO UNIVERSITARIO DE LOS VALLES
Monitoring Hidrological Variations using Multispectral Monitoring Hidrological Variations using Multispectral SPOT-5 Data: Regional Case of Jalisco in MexicoSPOT-5 Data: Regional Case of Jalisco in Mexico
Dr. Iván Esteban Villalón Turrubiates, Dr. Iván Esteban Villalón Turrubiates, Member,Member, IEEE IEEE
OverviewOverview
- AbstractAbstract- Remote Sensing DefinitionRemote Sensing Definition- Sensor ResolutionSensor Resolution- Introduction to Image ClassificationIntroduction to Image Classification- Model FormalismModel Formalism- Verification ProtocolsVerification Protocols- Simulation ExperimentsSimulation Experiments- Concluding RemarksConcluding Remarks
AbstractAbstractProposition - A new and efficient classification approach of remote sensing signatures extracted from large-scale multispectral imagery.
Contribution - This approach exploits the idea of combining the spectral signatures from a remote sensing image to perform a novel and accurate classification technique.
Verification - Simulation results are provided to verify the efficiency of the proposed approach.
REMOTE SENSING REMOTE SENSING DEFINITIONDEFINITION
Remote SensingRemote SensingRemote Sensing can be defined as:
"The arte and science to obtain data from an object avoiding direct contact with it” (Jensen 2000).
There is a transmission medium involved?
Remote SensingRemote SensingOf the Environment:
… is the collection of information regarding our Planet surface and its phenomena involving sensors that are not in direct contact with the studied area.
The main focus is in recollected information from a spatial perspective throughout electromagnetic radiation transmission.
Remote SensingRemote Sensing
Sensor election.
Reception, storage and digital signal processing of the data.
Analysis of the resulting information.
A) Illumination Source
B) Radiation
C) Interaction with the object
D) Radiation sensing
E) Transmission, reception and data processing
F) Analysis and interpretation
G) Application
ProcessProcess
SENSOR RESOLUTIONSENSOR RESOLUTION
ResolutionResolution All remote sensing systems use four types of
resolution:
Spatial
Spectral
Temporal
Radiometric
Spatial ResolutionSpatial Resolution
Spectral ResolutionSpectral Resolution
Time
July 1 July 12 July 23 August 3
11 days
16 days
July 2 July 8 August 3
Temporal ResolutionTemporal Resolution
6-bits Range0 63
8-bits Range0 255
010-bits Range
1023
Radiometric ResolutionRadiometric Resolution
INTRODUCTION TO IMAGE INTRODUCTION TO IMAGE CLASSIFICATIONCLASSIFICATION
Image ClassificationImage Classification Why classify?
Make sense of a landscape Place landscape into categories (classes)Forest, Agriculture, Water, Soil, etc.
Classification scheme = structure of classes Depends on needs of users.
Typical usesTypical uses Provide context
Landscape planning or assessment Research projects Natural resources management Archaeological studies
Drive models Meteorology Biodiversity Water distribution Land use
Example: Near Mary’s PeakExample: Near Mary’s Peak•Derived from a 1988 Landsat TM image
•Distinguish types of forest
Open
Semi-open
Broadleaf
Mixed
Young Conifer
Mature Conifer
Old Conifer
Legend
Classification: Critical PointClassification: Critical Point LAND COVER not necessarily equivalent to LAND USE We focus on what’s there: LAND COVER Many users are interested in how what is there is being
used: LAND USE
Example Grass is land cover; pasture and recreational parks are
land uses of grass
Basic Strategy: How to do it? Basic Strategy: How to do it? Use radiometric properties of remote sensor Different objects have different spectral signatures
In an easy world, all “vegetation” pixels would have exactly the same spectral signature.
Then we could just say that any pixel in an image with that signature was vegetation.
We could do the same for soil, water, etc. to end up with a map of classes.
Basic Strategy: How to do it? Basic Strategy: How to do it?
But in reality, that is not the case. Looking at several pixels with vegetation, you’d see variety in spectral signatures.
The same would happen for other types of pixels, as well.
Basic Strategy: How to do it? Basic Strategy: How to do it?
The Classification Trick: The Classification Trick: Deal with variabilityDeal with variability
•Different ways of dealing with the variability lead to different ways of classifying images.
•To talk about this, we need to look at spectral signatures a little differently.
Think of a pixel’s brightness in a 2-Dimensional space. The pixel occupies a point in that space.
The vegetation pixel and the soil pixel occupy different
points in a 2-D space.
With variability, the vegetation pixels now
occupy a region, not a point, of n-Dimensional space.
Soil pixels occupy a different region of n-Dimensional space.
• Classification: • Delineate boundaries of classes in n-dimensional space• Assign class names to pixels using those boundaries
Basic Strategy: Basic Strategy: Deal with variabilityDeal with variability
Classification StrategiesClassification StrategiesTwo basic strategies:
Supervised Classification We impose our perceptions on the spectral data.
Unsupervised Classification Spectral data imposes constraints on our interpretation.
Digital Image
Supervised ClassificationSupervised Classification
The computer then creates...
Supervised classification requires the analyst to select training areas where he knows what is
on the ground and then digitize a polygon within that area…
Mean Spectral Signatures
Known Conifer Area
Known Water Area
Known Deciduous Area
Conifer
Deciduous
Water
Multispectral ImageInformation
(Classified Image)
Mean Spectral Signatures
Spectral Signature of Next Pixel to be
Classified
Conifer
Deciduous
Water Unknown
Supervised ClassificationSupervised Classification
Water
Conifer
Deciduous
Legend:
Land Cover Map
The Result: Image SignaturesThe Result: Image Signatures
Unsupervised ClassificationUnsupervised Classification In unsupervised classification, the spectral data imposes constraints on our interpretation.
How? Rather than defining training sets and carving out pieces of n-Dimensional space, we define no classes beforehand and instead use statistical approaches to divide the n-Dimensional space into clusters with the best separation.
After the fact, we assign class names to those clusters.
Unsupervised ClassificationUnsupervised Classification
Digital Image
The analyst requests the computer to examine the image and extract a number of spectrally distinct
clusters… Spectrally Distinct Clusters
Cluster 3
Cluster 5
Cluster 1
Cluster 6
Cluster 2
Cluster 4
Saved Clusters
Cluster 3
Cluster 5
Cluster 1
Cluster 6
Cluster 2
Cluster 4
Unsupervised ClassificationUnsupervised ClassificationOutput Classified Image
Unknown
Next Pixel to be Classified
Unsupervised ClassificationUnsupervised Classification
Conif.
Hardw.
Water
Land Cover Map Legend
Water
Water
Conifer
Conifer
Hardwood
Hardwood
Labels
It is a simple process to regroup (recode) the clusters into
meaningful information classes (the legend).
The result is essentially the same as that of the
supervised classification:
MODEL FORMALISMMODEL FORMALISM
Multispectral ImagingMultispectral Imaging Is a technology originally developed for space-based imaging.
Multispectral images are the main type of images acquired by remote sensing radiometers.
Usually, remote sensing systems have from 3 to 7 radiometers; each one acquires one digital image in a small band of visible spectra, ranging 450 to 690 nm, called red-green-blue (RGB) regions: Blue -> 450-520 nm. Green -> 520-600 nm. Red -> 600-690 nm.
The combination of the RGB spectral bands generates the so-called True-Color RS images.
Statistical Approach.
Assume normal distributions of pixels within classes.
For each class, build a discriminant function For each pixel in the image, this function calculates the
probability that the pixel is a member of that class. Takes into account mean and variance of training set.
Each pixel is assigned to the class for which it has the highest probability of membership.
Weighted Pixel Statistics MethodWeighted Pixel Statistics Method
Blue Green Red Near-IR Mid-IR
Mean Signature 1
Candidate Pixel
Mean Signature 2
It appears that the candidate pixel is closest to Signature 1. However, when
we consider the variance around the signatures…
Rel
ativ
e R
efle
ctan
ce
Weighted Pixel Statistics MethodWeighted Pixel Statistics Method
Blue Green Red Near-IR Mid-IR
Mean Signature 1
Candidate Pixel
Mean Signature 2
The candidate pixel clearly belongs to the signature 2 group.
Rel
ativ
e R
efle
ctan
ce
Weighted Pixel Statistics MethodWeighted Pixel Statistics Method
Weighted Pixel Statistics MethodWeighted Pixel Statistics Method
Weighted Pixel Statistics MethodWeighted Pixel Statistics Method
VERIFICATION PROTOCOLSVERIFICATION PROTOCOLS
Verification ProtocolsVerification ProtocolsA set of three synthesized images are used as verification protocols.
All synthesized images are True-Color (RGB), presented in 1024-by-1024 pixels (TIFF format).
Each synthesized image contains three different regions (in yellow, blue and black colors) with a different pattern.
The developed Weighted Pixel Statistics (WPS) algorithm is compared with the most traditional Weighted Order Statistics (WOS) method [S.W. Perry, H.S. Wong, 2002].
Results:Results:11stst Synthesized Scene Synthesized Scene
Synthesized SceneSynthesized Scene WOS ClassificationWOS Classification WPS ClassificationWPS Classification
Quantitative ComparisonQuantitative Comparison11stst Synthesized Scene Synthesized Scene
Results:Results:22ndnd Synthesized Scene Synthesized Scene
Synthesized SceneSynthesized Scene WOS ClassificationWOS Classification WPS ClassificationWPS Classification
Qualitative ComparisonQualitative Comparison22ndnd Synthesized Scene Synthesized Scene
Synthesized SceneSynthesized Scene WOS ClassificationWOS Classification WPS ClassificationWPS Classification
Quantitative ComparisonQuantitative Comparison22ndnd Synthesized Scene Synthesized Scene
Results:Results:33rdrd Synthesized SceneSynthesized Scene
Synthesized SceneSynthesized Scene WOS ClassificationWOS Classification WPS ClassificationWPS Classification
Qualitative ComparisonQualitative Comparison33rdrd Synthesized Scene Synthesized Scene
Synthesized SceneSynthesized Scene WOS ClassificationWOS Classification WPS ClassificationWPS Classification
Quantitative ComparisonQuantitative Comparison33rdrd Synthesized Scene Synthesized Scene
RemarksRemarksThe quantitative study is performed calculating the classified percentage obtained with the WOS and WPS methods, respectively.
The WOS method uses only 1 spectral band.
The WPS method uses the information from the three spectral bands to analyze the pixel-level neighborhood means and variances.
The results shows a more accurate and less smoothed identification of the classes.
SIMULATION EXPERIMENTSSIMULATION EXPERIMENTS
Archaeological Land UseArchaeological Land UseA Remote Sensing Signatures (RSS) electronic map is extracted from the multispectral image. Three level RSS are selected for this particular simulation process, defined as:
██ – Archaeological land use zones.
██ – Modern land use zones.
██ – Natural land cover zones.
██ – Unclassified zones.
Archaeological SiteArchaeological Site"Guachimontones", Jalisco Mexico"Guachimontones", Jalisco Mexico
Simulation ResultsSimulation ResultsScene from "Guachimontones"Scene from "Guachimontones"
Original SceneOriginal Scene WPS ClassificationWPS Classification
Hidrological VariationsHidrological VariationsA Remote Sensing Signatures (RSS) electronic map is extracted from the multispectral image. Three level RSS are selected for this particular simulation process, defined as:
██ – Humid zones.
██ – Dry zones.
██ – Wet zones.
██ – Unclassified zones.
Simulation ResultsSimulation ResultsScene from "La Vega" dam, Jalisco MexicoScene from "La Vega" dam, Jalisco Mexico
Original SceneOriginal Scene WPS ClassificationWPS Classification
CONCLUDING REMARKSCONCLUDING REMARKS
RemarksRemarksThe WOS classifier generates several unclassified zones because it uses only one spectral band in the classification process.
The WPS classifier provides a high-accurate classification without unclassified zones because it uses more robust information in the processing.
The qualitative and quantitative analysis probe the efficiency of the proposed approach.
Future WorkFuture WorkComparison with several classification techniques.
A more extensive performance analysis of the proposed approach with different synthesized images.
Application to remote sensing imagery and the study of its performance.
Hardware implementation of the proposed approach.
Dr. Iván Esteban Villalón Turrubiates, Dr. Iván Esteban Villalón Turrubiates, Member,Member, IEEEIEEE
UNIVERSIDAD DE GUADALAJARAUNIVERSIDAD DE GUADALAJARACENTRO UNIVERSITARIO DE LOS VALLESCENTRO UNIVERSITARIO DE LOS VALLES
THANK YOU!THANK YOU!Questions?Questions?