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5. Texture

The chapter introduces key concepts in image interpretation, outlining the significance of texture, pattern, shape, size, shadow, and site/association. It further explores digital image interpretation methods, emphasizing the differences between visual and digital techniques, and details the processes of image pre-processing, enhancement, transformations, and classification. An assessment of accuracy is critical for evaluating the quality of classified maps derived from remote sensing data.

Sections

Texture

Texture refers to the arrangement and variation of tones in an image, influencing the overall appearance and discernibility of visual features.

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Pattern

The section on pattern focuses on the spatial arrangement and repetition of objects, highlighting its significance in distinguishing features in images.

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Shape

Shape refers to the distinct form or outline of objects, serving as a critical clue in image interpretation.

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Size

This section discusses the concept of size in remote sensing, particularly how it relates to the scale of images, and its significance in distinguishing various features.

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Shadow

The section discusses the significance of shadow in the interpretation of images, detailing how it can assist in determining object height and identifying shapes while also acknowledging the limitations shadows impose.

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Site/Association

This section explores the concepts of site and association in remote sensing, detailing their significance in spatial analysis.

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Digital Image Interpretation Methods

This section focuses on digital image interpretation methods for processing optical remote sensing images, highlighting techniques for effective image analysis.

5.17 Section Overview

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5.17.1 Image pre-processing

Image pre-processing is the initial stage of processing raw image data to correct for geometric distortions, calibrate radiometric data, and remove noise.

5.17.1.A Geometric Corrections

This section discusses the fundamental steps involved in geometric corrections of digital images used in remote sensing.

5.17.1.A.i Georeferencing

Georeferencing is the process of aligning digital images with their corresponding geographic coordinates to enable accurate analysis and comparison.

5.17.1.A.ii Resampling

Resampling is the process of altering the pixel values of an image to match a new coordinate system following georeferencing, essential for maintaining accuracy in digital image processing.

5.17.1.B Atmospheric Correction

Atmospheric correction is a crucial step in modifying digital numbers (DN) in remote sensing images to mitigate the noise effects introduced by the atmosphere.

5.17.2 Image enhancement

Image enhancement aims to improve the quality and interpretability of images by increasing contrast without adding information.

5.17.2.A Image Histogram

An image histogram is a graphical representation that shows the distribution of digital numbers (DN) in an image, which aids in image enhancement and interpretation.

5.17.2.B Contrast Enhancement

This section discusses the importance of contrast enhancement in image processing, focusing on techniques and methods for improving visual quality and interpretability of images.

5.17.2.C Image Transformations

Image transformations use mathematical functions to create new images that enhance specific features of original images.

5.17.3 Digital image classification

This section discusses digital image classification methods for optical and microwave images, focusing on their spectral signatures and classification techniques.

5.17.3.A Supervised Classification

Supervised classification involves identifying known classes in digital images to categorize all pixels based on their spectral signatures.

5.17.3.B Unsupervised classification

Unsupervised classification is a method of digital image classification based purely on the spectral properties of pixels.

5.17.4 Accuracy assessment

This section emphasizes the importance of accuracy assessment in remote sensing image classification, addressing potential errors and methods for evaluating classification quality.

Learning Objectives

  • Texture is a critical aspect for visualizing smoothness or coarseness in images.

  • Digital image processing involves several stages, including pre-processing, enhancement, transformation, and classification.

  • Both supervised and unsupervised classifications have their applications and relevance in remote sensing image analysis.

Key Concepts

Texture

The arrangement and frequency of tonal variation in an image that helps determine the overall smoothness or coarseness of features.

Georeferencing

The process of converting image coordinates to ground coordinates to remove distortions caused by sensor geometry.

Supervised Classification

A classification method where an analyst uses a priori knowledge to identify training sites and classify pixels based on their DN values.

Unsupervised Classification

A classification method that groups DN values without the need for prior knowledge of specific land cover types.

Error Matrix

A tool used for assessing the accuracy of a classification by comparing classified data against reference data.

Practice Exercises

Total Questions

2

Estimated Time

4 min

Passing Score

70%

Instructions

  • Read each question carefully
  • You can use hints if you need help
  • Complete all questions before submitting

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