Concepts & Foundations of Remote Sensing

1. Concepts & Foundations of Remote Sensing L&K pages 1 – 12 GEO 410 Dr.Garver

2. Powerpoints: 3_energy.ppt & 4_LK_pg1-12.ppt • Readings: Sections 1.1 to 1.4 of online text & LK1 reading • Concepts/Calculations: • EMR, EMS • Wavelength vs. frequency • Visible, IR (near IR, Thermal IR) • Reflected vs. emitted • SB Law, Weins Law – Sun/Earth example • How energy interacts with atmosphere (absorption, scattering (3 types), reflection) • Albedo • Atm. Windows, main gases that absorb Quiz 1

3. Defines r.s. • Electromagnetic energy sensors on airborne and spaceborne platforms • Sensors acquire data on the way earth/atm features reflect and emit EMR. 1.1 Introduction

4. Electromagnetic r.s. of earth resources • Illustrates generalized process and elements involved in r.s. • Data acquisition (a to f) – GEO 410 • a – d <= energy/atm • e - f <= sensors/data • Data analysis (g to h) – GEO 420 • interpretation/analysis/output/GIS/end users Figure 1

5. Fundamentals of EMR • Interactions w/atm • Interactions with surface • Ideal r.s. system • Limitations • Close relationship between r.s., GPS and GIS Remainder of chapter – Basic principles of r.s.

6. EM spectrum • C = vl (1.1) • Wave theory - EM waves obey this eqn • Categorize EMR by wavelength along spectrum 1.2 Energy Sources & Radiation Principles

7. VISIBLE = 0.4 – 0.7 • Blue = 0.4 - mm 0.5 mm • Green= 0.5 - 0.6 mm • Red= 0.6 - 0.7 mm • IR – only thermal IR is related to heat • Wave theory C = vl eqn 1.1 • Particle Theory Q = hv eqn 1.2 • Discrete photons • Can relate these two models: • Q= hc/l eqn 1.3 1.2 Energy Sources & Radiation Principles

8. Energy is inversely proportional to wavelength. • Longer wavelength = less energy • Implication for r.s.- microwave harder to detect than VIS or IR. • Systems operating at longer wavelengths need to view large areas of earth to get a detectable signal. 1.2 Energy Sources & Radiation Principles

9. Sun is source of EMR for r. s. • But, all matter at T above absolute zero (0 K) emits EMR. • So, terrestrial objects are also sources of radiation but at a different wavelength and magnitude. • SB Law (1.4) • Energy emitted varies as T4

10. Blackbody – hypothetical ideal radiator • Absorbs and emits all energy equally • Dominant wavelength • Wein’s law (1.5) • Figure 1.4 – spectral distribution of energy • Sun vs. Earth • Dividing line between reflected and emitted • Radar – active not passive (supplies own energy source) • Flash on a camera

11. All radiation detected by sensors passes through some pathlength of atm • Scattering – unpredictable - different size particles • Absorbers – effective loss of energy, most effective absorbers (water vapor, CO2, O3) • Atmospheric windows – wavelengths on which the atm is particularly transmissive. • Fig. 1.5 1.3 Energy Interactions in Atm

12. 2 Energy Sources Used in R. S. R. S. is limited to Atmospheric Windows Common Sensors Fig. 1.5

13. Fig. 1.5 • Vis range coincides with an atm window • Thermal IR bands: 3 - 5 mm and 8 – 14 mm • Multispectral scanners – sense simultaneously through multiple narrow wavelength windows through Vis and IR • Radar and passive micro: 1mm – 1m window

14. Take home message: • Interaction and interdependence between primary sources of EMR, atm windows and spectral sensitivity of sensors. • Need to consider 1) spectral sensitivity of sensors available, • 2) presence/absence of atm windows in the spectral range you are interested in, and • 3) the source, magnitude , and spectral composition of the energy available in these ranges. • End of section 1.3