some important information about the digital image processing in world.

1. Digital Image Processing
 Definition:
Computer-based manipulation and interpretation of digital images.

2. Digital Image Processing
 Five broad types of computer assisted operation:
1. Image rectification and restoration (preprocessing
2. Image enhancement
3. Image classification (spectral vs. spatial pattern recognition)
4. Data merging and GIS integration
5. Hyperspectral image analysis
6. Biophysical modeling
7. Image transmission and compression

3. Image Rectification
& Restoration
 Preprocessing to correct distorted or degraded image data
 Geometric distortions
 Radiometric calibration
 Elimination of noise

4. Image Enhancement
 To more effectively display or record the data, increasing
the visual distinctions between features in a scene
 Contrast manipulation: stretching

5. Image Classification
 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

6. 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.

7. Examples of Classification
Results

8. Data Merging
and GIS Integration
 To combine image data with other geographically
referenced datasets for the same area
 Multitemporal data merging
 Change detection procedures
 Multisensor image merging

9. Image Rectification &
Restoration
 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

10. Image Rectification
& Restoration

11. Digital images
 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.

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

13. Geometric Correction
 Raw digital images usually contain geometric distortions so
significant that they cannot be used directly as a map base
without subsequent processing.
 Distortion ()-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

14. Image registration (or
resampling)
 Resampling -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 : technique, the transformed pixel
takes the value of the closest pixel in the pre-shifted array.
 Bilinear Interpolation :uses the 4 closest pixel values
surrounding the transformed output pixel is used.
 Cubic Convolution : uses the 16 closest pixel values

15. Image registration (or
resampling)

16. Image registration (or
resampling)

17. (Radiometric correction)(Radiometric correction)
Atmospheric EffectsAtmospheric Effects
LP
TE
LAPP +
Π
=
ρ
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