Remote Sensing and GIS Application - PowerPoint Presentation

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Remote Sensing and GIS Application

LecturerRuba Yousif HussainThird Year

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Image EnhancementImage Enhancement

The goal of image enhancement is to improve the visual interpretability of an image by increasing the apparent distinction between the features in the scene.  Enhancement operations are normally applied to image data after the appropriate restoration procedures have been performed .  Digital enhancement techniques can be categorized as 1- Contrast Manipulation - Gray level thresholding - level slicing - contrast stretching 2- Spatial feature manipulation - Spatial filtering - edge enhancement - Fourier analysis

 3- Multi-image manipulation

- Multispectral band

ratioing and differencing - principal components - canonical components - vegetation components - intensity-hue-saturation ( IHS ) color space transformation - decorrelation stretching

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Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain

The visual quality of an image is related to the range of brightness in the image , known as contrast .A high contrast image has a narrow range of brightness mainly blacks and whites . A low contrast image has a wide range of brightness .

 Three most important enhancement techniques  1- Radiometric Enhancement Enhancing image based on the values of individual pixels  2- Spectral EnhancementEnhancing image by transforming the values of each pixel on a multiband basis ( Band Ratios , Vegetation Indices , Tasseled Cap ) 3- Spatial Enhancement

Enhancing image based on the values of individual and neighboring pixels.

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Remote Sensing and GIS Application Lecturer

Third Year Ruba Yousif Hussain

ContrastBrightnessTransparency

GammaDynamic Range AdjustmentBackground  Zoom To raster Resolution4

Remote Sensing and GIS Application Lecturer

Third Year Ruba Yousif Hussain

Laboratory

Radiometric Enhancement of Imagery

Purpose

Enhancing image based on the values

of individual pixels .

Application

ArcGIS

Tutorial

Using

ArcGIS

as a Viewer

for Radiometric Enhancement Image Analysis WindowImage Analysis Window changes the image on display but does not change the file (original image).

Contrast changes the range of differences between the darkest and lightness objectsBrightness

will make the image appear lighter or darkerTransparencydisplay the image so you can see the image below itGamma controls relationships between the brightness of original scene and that on the display For example Gamma = 1 , the two images will use the same scale of brightnessesGamma = 0.5 or 1.5 , the display shows , respectively , either compressed , or expanded, scale of brightness relative to the original.Background eliminates the no data value in the display. 

Histograms

Histograms plot the frequency values of the digital numbers ( DNs ) ( x-axis ) against the number of pixels with that value ( y-axis ) .

Remember , the shape of the histogram is determined by the features represented in the image , and their brightnesses ) . ArcMap displays histograms in two ways First

: Layer Properties / Symbology tab.

5Remote Sensing and GIS Application Lecturer

Third Year

Ruba

Yousif

Hussain

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Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain

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Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain

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Remote Sensing and GIS Application Lecturer Third Year Ruba Yousif Hussain

Second

: Image Analysis window