Remote Sensing

1
Remote Sensing
Image Processing Geometric Rectification
2
Remote Sensing

• What is geometric rectification?
• The conversion of satellite image coordinate
  system to a standard map projection
• Why is it necessary?
• Accurate location within an image
• Importing remote sensing data to GIS

3
Remote Sensing

• Satellite Imaging Systems
• Scan mirror

4
Remote Sensing

• Satellite Imaging Systems
• Scan mirror
• Linear Array

5
Remote Sensing

• Satellite Imaging Systems
• Scan mirror
• Linear Array
• Area array

6

Remote Sensing

• Systematic Distortions in Satellite Imaging
  Systems
• Panoramic Distortion
• Platform velocity
• Earth rotation
• Spacecraft altitude
• Terrain

7

Remote Sensing

• Additional Distortions in Scan Mirror Systems
• Scan Skew
• Mirror-scan velocity

8

Remote Sensing

• Distortions due to Spacecraft Systems
• Scan Skew
• Mirror-scan velocity
• Can be corrected using spacecraft design data
• Platform velocity
• Spacecraft altitude
• Can only be corrected using telemetry from the
  speccraft

9

Remote Sensing

• Panoramic Distortion
• Due to spacing of detectors and regular sampling
• Increases with swath
• Corrected using orbital model

10

Remote Sensing

• Earth Rotation
• Due to time taken to build an image
• Each line offset to the west from the previous
  one
• Corrected using orbital model

11

Remote Sensing

• Earth Rotation
• Due to time taken to build an image
• Each line offset to the west from the previous
  one
• Corrected using orbital model

12

Remote Sensing

• Terrain
• Due to small changes in altitude and aspect
• Can be corrected by ortho-rectification
• Requires a DEM
• Can be corrected using a rubber sheet
  rectification based on ground control points.

13
Remote Sensing

• Rectification
• Based on ground control point selection
• Establishes a relationship between the image
  coordinate system and the map coordinates
• Rubber sheet the image coordinates to match
  those of the ground control points
• Use interpolation to determine the reflectance
  value for the new grid points.

14

Remote Sensing

• Ground Control Points

15

Remote Sensing

• Interpolation of Reflectance Values

16

Remote Sensing

• Interpolation of Reflectance Values