Lec 9 - Fundamentals of Image Interpretation Flashcards
Aspects of Image Interpretation (3)
(1) The portrayal of features from an overhead, often unfamiliar, perspective;
(2) The frequent use of wavelengths outside the visible portion of the spectrum; and
(3) The depiction of the earth’s surface at unfamiliar scales and resolution.
The process of identifying objects or conditions in images and determining their meaning or significance.
Image Interpretation
Use scientific tools and methodology to arrive at objective findings.
The Interpreter’s Task
This is needed to relate the visible characteristics of the image to the real-world geographical features, even though some of these features may not be physically visible.
Geographical knowledge
Image Interpretation Process (3)
(1) Image
(2) Interpretation Process (Interpreter’s skills and knowledge level)
(3) Information (quality or quantity)
Requirements of Image Interpretation (4)
(1) Remote Sensing System
(2) Knowledge of image and sensor characteristics
(3) Proficiency based on knowledge of the subject
(4) Adequate familiarity of the geographic region and locality
This means identifying geographical features using spatial characteristics of objects shown on images. The most important task for this is to establish interpretation keys, i.e. identifying the typical spatial patterns of known geographical features.
Spatial Interpretation
Levels of Interpretation (3)
(1) Image Reading
(2) Image Analysis
(3) Image Interpretation
A relatively superficial visual examination of an image undertaken to quickly identify the main features and determine their distribution and likely relationship.
Image Reading
Image reading with longer and more detailed visual inspection of the imagery to understand the more general and obvious features in the imagery.
Image Analysis
Inductive and deductive analysis of imagery, in conjunction with other data, to gain as full an understanding as possible of the features in the imagery, their functions and their inter-relationships.
Image Interpretation
Before Delineating Separate Aerial Units (2)
(1) Classification System (Thematic Level Of Classification)
(2) Minimum Mapping Unit (MMU)
Criteria to be used to separate the various categories of features occurring in images.
Classification System (Thematic Level Of Classification)
Classification System (Thematic Level Of Classification) (6)
(1) Agricultural
(2) Residential
(3) Commercial
(4) Industrial
(5) Rural
(6) Urban/Built-up
Image Interpretation Elements (8)
(1) Shape
(2) Size
(3) Pattern
(4) Shadow
(5) Tone or Hue
(6) Texture
(7) Association
(8) Site
Ordering of Elements in Image Interpretation (4)
(1) Primary
(2) Secondary
(3) Tertiary
(4) Higher
Basic Element in Primary Degree of Complexity
Tone/Color
Basic Elements in Secondary Degree of Complexity (3)
(1) Size
(2) Shape
(3) Texture
Basic Elements in Tertiary Degree of Complexity (2)
(1) Pattern
(2) Shadow
Basic Elements in Higher Degree of Complexity (2)
(1) Site
(2) Association
The measure of the intensity of the reflected or emitted radiation of the objects of the terrain.
Tone or Color
Refers to the frequency of tonal variation in an image. This is produced by an aggregate unit of features which may be too small to be clearly discerned individually on the image.
Texture
It is always scale or resolution dependent.
Texture
Same reflected objects that have differences in this helps in their identification.
Texture
This must be considered in the context of the image scale or resolution.
Size
Most measured parameters (5)
(1) Length
(2) Width
(3) Perimeter
(4) Area
(5) Volume
Refers to the general form, configuration or outline of an individual object.
Shape
It is one of the most important single factors for recognizing objects from an image.
Shape
Refers to the spatial arrangement of the objects.
Pattern
The characteristic of this element in image interpretation is the repetition of certain general form or relationship in tones and texture.
Pattern
A helpful element in image interpretation but also creates difficulties for some objects in their identification in the image.
Shadow
It is also useful for enhancing or identifying topography and landforms, particularly in radar imagery.
Shadow
Refers to the occurrence of certain features in relation to other objects in the imagery.
Association
In urban areas this generally refers to a playground or grass land not agricultural land.
A smooth vegetation pattern
Refers to topographic or geographic location. It is also an important element in image interpretation when objects are not clearly identified using the previous elements.
Site
The criterion for identification of an object with interpretation elements. Provides guidance about the correct identification of features or conditions on the images.
Interpretation key
Types of Interpretation Keys (2
(1) Selection Key
(2) Elimination Key
Contains numerous photographic examples with supporting text.
Selection Key
Arranged so that the interpretation proceeds step-by-step from the general to the specific details and leads to the elimination of all features or conditions except the one being identified.
Elimination Key
These are employed to interpret multispectral images.
Spatial Interpretation Keys
Properties Influencing Electromagnetic Spectrum (2)
(1) Chemical Properties
(2) Physical Properties
The major factor in the VIS/IR region. Visible and near-infrared sensors record the reflected sunlight to acquire information about the chemical composition of the objects being observed.
Chemical Properties
These sensors record the reflected sunlight to acquire information about the chemical composition of the objects being observed.
Visible and near-infrared sensors
The major factor in the thermal IR and upper microwave region.
Physical Properties
These sensors record the emitted radiation from the earth surface or atmosphere and are used to acquire information about the thermal properties as well as the composition of the object.
Thermal infrared and passive microwave sensors
MS Data Interpretation (5)
(1) Different Color Modes To Display Imagery
(2) Single Band
(3) Multispectral Bands
(4) Three bands can be simultaneously displayed
(5) Trial-and-error approach to produce the right contrast and highlights to right features
Spectral Interpretation Key (6)
(1) Farmland
(2) Swamps/Mangroves
(3) Dike or Ponds
(4) Built-up Areas
(5) Bare Ground
(6) Water Body
Covered with actively growing crops showing typical vegetation signatures on the MS image.
Farmland
Strong vegetation signals are shown on the multispectral image.
Swamps/Mangroves
The cover type is basically the mixture of water and farmland in a repeating pattern.
Dike or Ponds
Spectral characteristic is quite unique, often with ‘darkened’ concrete spectral signals, that is related to the shadow of buildings.
Built-up Areas
Characterized by those where the native vegetation cover has been completely removed, showing strong reflectance in all bands.
Bare Ground
When the water is deep enough (i.e. no reflectance from the bottom of the water) and clean enough (i.e. not containing too much sediment), this cover type can be clearly identified. When they are shallow and muddy, they create significant confusion in the classification process.
Water Body
This uses multi-temporal images to identify the change and movement. It is based on spatial and spectral interpretation.
Temporal Interpretation
It adds the temporal dimension for image interpretation. It is important for image interpretation because factors such as vegetation growth and soil moisture vary during the year.
Temporal Interpretation
Temporal interpretation is based on these interpretation. (2)
(1) Spatial Interpretation
(2) Spectral Interpretation
Sequence Of Image Interpretation (8)
(1) Understand the goals of the interpretation task.
(2) Describe characteristics of area and processes to be interpreted.
(3) Validate the generalized understanding of the area and problem.
(4) Plan the information sources needed.
(5) Acquire the image data, facilities required.
(6) Conduct the interpretation.
(7) Field inspection to resolve conflicts or confusion
(8) Assess accuracy
