Processing of Satellite Image Using Digital Image Processing

7/28/2019 Processing of Satellite Image Using Digital Image Processing

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Processing of Satellite Imageusing Digital Image

Processing

Presenters:Sana Ullah (4849)

Zabeehullah (4893)

Sohail Ahmad (4895)


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Contents Image Processing

Purpose of Image Processing Satellite Image Digital Image Color Composition

False Color True Color

Image Rectification and Restoration

Ground Control Points (GCP) Bit Error Resampling Striping

Image Enhancement Contrast Enhancement Spatial Filtering

Information Extraction Image Classification Unsupervised Classification Supervised Classification Accuracy and Error

Conclusion


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Image Processing

Analyzing and manipulating images with acomputer for information extraction is known asimage processing. Image processing generallyinvolves three steps:o Import an image with an optical scanner or directly through digital

photography.o Manipulate or analyze the image in some way. This stage can include

image enhancement and data compression, or the image may be

analyzed to find patterns that aren't visible by the human eye. For

example, meteorologists use image processing to analyze satellite

photographs.

o

Output the result. The result might be the image altered in some way or itmight be a report based on analysis of the image.


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Purpose of Image Processing

The purpose of image processing is divided into 5groups. They are:o Visualization - Observe the objects that are not visible.

o Image sharpening and restoration - To create a better image.

o Image retrieval - Seek for the image of interest.

o Measurement of patternMeasures various objects in an image.

o Image RecognitionDistinguish the objects in an image.


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Satellite Image Satellite images are images captured by satellites at

regular intervals (usually hourly) and used bymeteorologists to forecast the weather. The threetypes of satellite imageryo Weather zone are infrared images

o

visible imageso water vapor images.


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Digital Image Digital imaging is the art of making digital images

photographs, printed texts, or artwork - through the use of adigital camera or image machine, or by scanning them as adocument.

Each image is compiled of a certain amount of pixels, whichare then mapped onto a grid and stored in a sequence by a

computer. Every pixel in an image is given a total value to determine its

hue or color.


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Color CompositionThere are two types of color composition :

False Color

True Color

False color refers to a group of color rendering methods used

to display images in color which were recorded in the visual ornon-visual parts of the electromagnetic spectrum.

A false-color image is an image that depicts an object incolors that differ from those a photograph (a "true-color"image) would show.


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Color Composition An image is called a "true-color" image when it offers a natural

color rendition, or when it comes close to it. This means that the colors of an object in an image appear to

a human observer the same way as ifthis observer were todirectly view the object:o A green tree appears green in the image, a red apple red, a blue sky

blue, and so on.o When applied to black-and-white images, true-colormeans that the

perceived lightness of a subject is preserved in its depiction.


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Image Rectification and RestorationGround Control Points (GCP)

Features with known locations on a map (X,Y coordinates).These are the ground control points

The same features can be accurately located on the imagesas well (column, row numbers).

The features must be well distributed on the map and theimage.

Highway intersections are commonly used ground controlpoints.

Bit Error Salt and pepper effect due to random error

Use 3x3 or 5x5 moving window average to remove the noise


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Image Rectification and RestorationResampling

The purpose is to assign pixel values to the empty pixels in therectified matrix output.

Superimpose the rectified output matrix to the distortedimage.

The digital number (DN) of a pixel in the output matrix isassigned based on the DN of its surrounding pixels in thedistorted image.

Striping

Malfunction of a detector

Use gray scale adjustment to correct the strips


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Striping

Resampling

Bit Error


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Image EnhancementSpatial Filtering

Techniques are based on direct manipulation of pixels in animage.

Used for filtering basics, smoothing filters, sharpening filters,unsharp masking and laplacian.


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Information ExtractionImage Classification

Categorize all pixels in image.

Spectral data.

Combinations of DNs.

Two approaches for image classification: Unsupervised classification.

Supervised Classification.


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Information ExtractionUnsupervised Classification

Examine unknown pixels in image.

Comparing data with reference data.

Common form of cluster K-means.

Applied on sub-areas of image.

Determine spectral separable class. More preferable than supervised.


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Information ExtractionSupervised Classification Examine known pixels in image.

Comparing data with reference data.

Information classified.

Basic Steps in supervised procedure

Training stage.

Feature selection.

Appropriate algorithm.

Post classification smoothening.

Accuracy assessment.


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Information Extraction


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Information ExtractionAccuracy and Error

The comparison of a classification with ground-truth data toevaluate how well the classification represents the real world.

Observations per class.

May take fewer samples of low variability classes likewater/forest.

Problems in classification

Sampling.

Reliable ground data.

Distribution.

Image Classifier

Ground Data


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Information Extraction


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ConclusionDigital image processing of satellite data can be primarily

grouped into three categories: Image Rectification and Restoration,

Enhancement and Information extraction.

Image rectification is the pre-processing of satellite data forgeometric and radiometric connections.

Enhancement is applied to image data in order to effectivelydisplay data for subsequent visual interpretation.

Information extraction is based on digital classification and isused for generating digital thematic map.


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References Digital Image Processing by Rafael C. Gonzalez.

www.wikipedia.org. www.earthobservatory.nasa.org.

IRSA Remote Sensing Image Processing System 5.2,6.0,2003.

Remote Sensing study based on IRSA Remote sensingProcessing System IEEE Xplore no 0-7803-8742-2/04 (c)2004

IEEE.
http://www.wikipedia.org/http://www.earthobservatory.nasa.org/http://www.earthobservatory.nasa.org/http://www.wikipedia.org/

Processing of Satellite Image Using Digital Image Processing

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