Digital Image Processing (معالجة الصور الرقمية) Definition: Computer-based manipulation and interpretation of digital images.

Digital Image Processing Five broad types of computer assisted operation: Image rectification and restoration (preprocessingا Image enhancement Image classification (spectral vs. spatial pattern recognition) Data merging and GIS integration Hyperspectral image analysis Biophysical modeling Image transmission and compression

Image Rectification & Restoration (تصحيح الصورة) Preprocessing (المعالجة الاولية) to correct (تصحيح)distorted or degraded image data (الصور المشوهة) Geometric distortions (التصحيحات الهندسية) Radiometric calibration(التصحيحات الاشعاعية) Elimination of noise (ازالة الضوضاء)

Image Enhancement (توضيح الصورة) To more effectively display or record the data, increasing the visual distinctions between features in a scene Contrast manipulation: stretching

Image Classification (تصنيف الصورة) To determine the land cover identity of each pixel in an image, replacing visual analysis with quantitative techniques Spectral pattern recognition: using only spectral radiances Spatial pattern recognition: using geometric shapes, sizes and patterns

Image Classification The overall objective of classification is to categorize all pixels in a digital image into one of several land cover classes Themes  thematic maps: A map designed to demonstrate particular features or concepts.

Examples of Classification Results

Data Merging and GIS Integration (دمج البيانات) To combine image data with other geographically referenced datasets for the same area Multitemporal data merging Change detection procedures Multisensor image merging

Image Rectification & Restoration (تصحيح الصورة) To correct image data for distortions or degradations stemming from the image acquisition process Varies with: Type of device (camera, scanner) Platform (airborne versus satellite) Total field of view- A sensor with a wide field of view can image the same place from different angles more frequently than a sensor in the same orbit with a narrower field of view and smaller swath

Image Rectification & Restoration

Digital images (الصور الرقمية) Remote sensing images are recorded in digital forms A digital image is a two-dimensional array of pixels. Each pixel has an intensity value (represented by a digital number) and a location address (referenced by its row and column numbers). They are distributed in computer compatible tapes (CCTs) The basic unit is pixel that is represented as a digital number (DN) Different data sets may use different number of bits so that bit scaling is common.

Image processing systems (انظمة المعالجة اللرقمية) Computer hardware (e.g. PC) Computer software Operating system (e.g. Windows/NT) Image processing software (e.g. ENVI) Operator (e.g. you)

Geometric Correction (التصحيح الهندسي) Raw digital images usually contain geometric distortions so significant that they cannot be used directly as a map base without subsequent processing. Distortion (التشوه)-changes in shape and position of objects with respect to their true shape and position. The source of distortions: Variations in altitude, attitude (position), and velocity of sensor platform Panoramic distortion Earth curvature Atmospheric refraction Relief displacement

Image registration (or resampling) (تسجيل الصورة) Resampling (تسجيل الصورة)-The calculation of new DN for pixels created during geometric correction of a digital scene, based on the values in the local area around the uncorrected pixels. In the Nearest Neighbor (الجار الاقرب) technique, the transformed pixel takes the value of the closest pixel in the pre-shifted array. Bilinear Interpolation (الزيادة الخطية):uses the 4 closest pixel values surrounding the transformed output pixel is used. Cubic Convolution (الالتواء المكعبي): uses the 16 closest pixel values

Image registration (or resampling)

Image registration (or resampling)

(Radiometric correction) (التصحيحات الاشعاعية) Atmospheric Effects Lapp=apparent radiance measured by sensor ρ = reflectance of object T = atmospheric transmittance E = irradiance on object, incoming Lp = path radiance/haze, from the atmosphere and not from the object