1. Data Preprocessing Dr Lewis RSU Geography UCL

2. Rationale when we view an RS image, we see a 'picture’

3. Rationale BUT need to be aware of the 'image formation process' to: –understand and use the information content of the image and factors operating on it –spatially reference the data when we view an RS image, we see a 'picture’

4. Overview Image formation process Sensor scanning systems Geometric distortions Radiometric distortions dealing with these effects applications –radiometric correction –geometric correction

5. Image formation process Generally, an RS instrument makes a measure of the radiation received at a sensor

6. Types of sensor: Source of Energy passive sensors –receive energy from a natural external energy source –e.g. reflected energy (originating at the Sun)

7. Types of sensor: Source of Energy passive sensors –receive energy from a natural external energy source –e.g. emitted energy (thermal or microwave)

8. Types of sensor: Source of Energy active sensors –emit energy from on-board source, and measure reflected energy –e.g. laser devices (LiDAR)

9. Types of sensor: Source of Energy active sensors –emit energy from on-board source, and measure reflected energy –e.g. RADAR

10. Types of sensor: Source of Energy active sensors –emit energy from on-board source, and measure reflected energy –e.g. RADAR

11. Types of sensor: Source of Energy Semi-active sensors –emit energy from one platform, and measure from another –e.g. target illumination