2. Learning Objectives Nature of Light Color & Spectroscopy ALTA Spectrophotometer Spectral Signature of Substances Interpretation of Satellite Images

3. Satellites Observe the Earth Resulting images yield valuable information about natural resources and the environment Special sensors are like sensitive cameras that can “see” invisible light

4. Light Has a Dual Nature Particles called photons Waves that can travel through the vacuum of space Einstein’s photoelectric effect demonstrates dual nature

5. What is Color? What color is the sky? What color is water? The color an object appears depends on the color of the light source and the pigments in object. How does sunlight shining through water droplets cause a rainbow?

6. Color Spectrum Light through a Prism Each wavelength band bends differently through prism

7. Electromagnetic Radiation Energy traveling outward, as in rays Waves through space –Periodic disturbances to electric and magnetic fields Speed of Light –C= 186,000 mi/sec or 300,000 km/sec

8. Electromagnetic Spectrum Visible bands (colors)are small portion of spectrum Long wavelengths to left are lower energy Short wavelengths to right are higher energy

9. What happens when light strikes matter? RedOrangeYellowGreenBlueViolet Reflected White Light Absorbed Transmitted Why do we see object as blue?

10. Spectroscopy: Science of Making & Studying Spectra Spectroscope: device that produces color spectrum Spectrometer: instrument that measures the intensity of light

11. ALTA II Reflectance Spectrometer Measures intensity of reflected light Provides its own light sources - Light Emitting Diodes (LEDs) Provides results comparable to data gathered from satellite spectroscopy

12. Spectral Signature Blue Green Yellow Orange Red Deep Red Near Infrared Cyan Example of a Graph of Data Collected From a Leaf With the ALTA

13. Remote Sensing Gathering information about something without actually touching it. Human eye acts as a remote sensor.

14. Remote Sensing Satellites remotely sense the Earth using spectroscopy Provides a wealth of information applying to many users including: –Agriculture –Environment –Natural Resources –Telecommunications –Utilities False Color Image of Orlando, Fla.; Courtesy of NASA.

15. Ground Truth Reference data collected on Earth –Aids in interpretation, analysis, and validation of remotely sensed data –Expensive and time consuming

16. Key for False Color Image Red: Healthy Vegetation Pink: Less Densely Vegetated Areas Tan Tan, Brown, Green With Patches of Red: Forest Dark Blue: Rivers, Lakes, Streams Light Blue Light Blue and Gray: Urban Areas, Cities, Towns White White: Bare Land, Fields, Soils

17. Remotely Sensed Image Image is composed of small dots, called picture elements (pixels) Scientist can extract information from every pixel

18. Operating the Alta On/Off LEDs & Detector Dark Voltage Standard White Card Reading

19. Data Table Green Leaf & Roofing Shingle

20. Sample Data Set Green Leaf & Roofing Shingle

21. Calculating Percent Reflectance For Green Leaf Perform the following steps for each ALTA data point (wavelength) Step 1 - Subtract dark voltage from standard white card reading and leaf reading. Step 2 - Divide resulting leaf reading by resulting standard white card reading. Step 3 - Multiply result of Step 2 by 100 Repeat Steps 1-3 for roofing shingle

22. Graph Template

23. Sample Graph