Fce 552 part6-4

Dept. of Geospatial & Space Technology

University of NairobiB. Sc. (Civil Engineering)

1.1. Procedures of Image ProcessingProcedures of Image Processing

2.2. Image Processing SystemsImage Processing Systems

3.3. Digital Image Processing – CorrectionDigital Image Processing – Correction

4.4. Digital Image Processing – ConversionDigital Image Processing – Conversion

5.5. Digital Image Processing – ClassificationDigital Image Processing – Classification

FCE 552: Engineering Survey IV

Digital Image Processing


University of NairobiEngineering Surveying IV

Procedures of Image Procedures of Image ProcessingProcessing



University of Nairobi


B. Sc. (Civil Engineering)

Data Flow in Remote Sensing





Data Processing in Remote Sensing





Image Processing SystemsImage Processing Systems





Image Processing Systems with Personal Computer





Image Processing Systems with Network System





Digital Image Processing - Digital Image Processing - CorrectionCorrection





Due to variations in scene illumination and Due to variations in scene illumination and

viewing geometry, atmospheric conditions, viewing geometry, atmospheric conditions,

and sensor noise and response will vary and sensor noise and response will vary

depending on the specific sensor and depending on the specific sensor and

platform used to acquire the data and the platform used to acquire the data and the

conditions during data acquisition; conditions during data acquisition;

It may be desirable to convert and/or It may be desirable to convert and/or

calibrate the data to known (absolute) calibrate the data to known (absolute)

radiation or reflectance units to facilitate radiation or reflectance units to facilitate

comparison between data. comparison between data.

Radiometric Distortion





Elements of Radiometric Correction





Atmospheric Effects





Atmospheric Correction



Due to several factors, including: the Due to several factors, including: the

perspective of the sensor optics; the motion perspective of the sensor optics; the motion

of the scanning system; the motion of the of the scanning system; the motion of the

platform; the platform altitude, attitude, and platform; the platform altitude, attitude, and

velocity; the terrain relief; and, the velocity; the terrain relief; and, the

curvature and rotation of the Earth. curvature and rotation of the Earth.

To correct for these errors geometric To correct for these errors geometric

registration of the imagery to a known registration of the imagery to a known

ground coordinate system must be ground coordinate system must be

performed i.e., performed i.e., georeferencing.georeferencing.



Geometric Distortions (1)





Geometric Distortions (2)



Flow of Geometric Correction





Relationship between Image andGround Control Systems





Example of Geometric Correction







Digital Image Processing - Digital Image Processing - ConversionConversion





Types of Image Conversion



Image Enhancement – Grey Scale Conversion





Image Enhancement – Histogram Equalization





Image Enhancement - Color Composition





Feature Extraction - Spatial Filtering





Normalized Difference Vegetation Index





Principal Component Analysis



The objective is to

reduce the dimensionality

in the bands thus

maximizing the amount of

information from the

original data into the

least number of new

components.



Principal Component Analysis







Digital Image Processing - Digital Image Processing - ClassificationClassification





Definition of Classification





Concept of Classification





Types of Classifications

Supervised classificationSupervised classification where the operator where the operator

defines the clusters during the defines the clusters during the training process training process

using training data obtained from using training data obtained from ground truthground truth..

Unsupervised classificationUnsupervised classification involves a involves a

clustering algorithmclustering algorithm automatically finding and automatically finding and

defining a number of clusters in the feature defining a number of clusters in the feature

space using only image characteristics or space using only image characteristics or

features.features.





Features for Classification

Multi-spectral featuresMulti-spectral features

Multi-temporal featuresMulti-temporal features

TextureTexture

Height information (DTM/DEM)Height information (DTM/DEM)

Indices (e.g., NDVI)Indices (e.g., NDVI)





Procedures of Classification





Comparison between different classifiers





Advanced Classifications

Fuzzy ClassificationFuzzy Classification

Contextual ClassificationContextual Classification

Artificial Neural Network ClassificationArtificial Neural Network Classification

Cognition-based ClassificationCognition-based Classification





Recognition of Man-made Objects





Example of Road Recognition





Example of Semi-automated Recognition of Houses



Depending on the application, the information of Depending on the application, the information of

classes of interest need to be defined and their classes of interest need to be defined and their

spatio-temporal characteristics assessed. On the spatio-temporal characteristics assessed. On the

basis of these, the most appropriate data can be basis of these, the most appropriate data can be

selected and the criteria include:-selected and the criteria include:-

Sensor type (resolution, level of detail, etc).Sensor type (resolution, level of detail, etc).

Relevant wavelength bands.Relevant wavelength bands.

Date of acquisition (important for phenomena that are Date of acquisition (important for phenomena that are

time dependent, also considerations in regard to cloud time dependent, also considerations in regard to cloud

cover and amount of illumination should be taken into cover and amount of illumination should be taken into

account.account.

Budgetary Criteria.Budgetary Criteria.

Remote Sensing Data Selection Criteria



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Fce 552 part6-4