1. Basics of Imaging systems Lecture 1 prepared by Rick Lathrop 8/02

2. Basics of Imaging Systems & Remote Sensing “Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation”.- Lillesand & Kiefer (1987) Alternative term: Digital Image Analysis

3. The remote sensing process Acquisition and analysis –Reading this viewgraph –eyes acquire the data, the brain processes it into information (I hope) –Aerial photography-the traditional means of remote sensing –Camera captures data with a lens system and chemical reactions on light sensitive films –Print is the storage and presentation media-eyes and brain process the data into useful information

4. Remote Sensing Model Remote sensing systems record reflected and/or emitted electromagnetic energy (i.e. light) as a 2D image. Of critical interest is how earth surface features (i.e. the target) interact and affect the reflected and/or emitted energy

5. The visible spectrum The visible spectrum is only a tiny window We are blind to 99.99% of the energy in the universe One of the strengths of remote sensing is that we have created devices that allow us to see beyond the range of human vision

6. The electromagnetic spectrum

7. Framing systems Instantaneously acquire an image Analog Camera - uses a lens to form an image at the focal plane. A shutter opens at selected intervals to allow light to enter, where the image is recorded on photographic film or an array of detectors Digital Camera - type of camera that records an image on an 2D array of photosensitive detectors that is then recorded as a digital image file

8. Aerial photos The traditional form of remote sensing Pro: Can be easily customized to meet specific requirements Historical archive Con: Can be expensive Need access to plane Visual interpretation Time consuming Repeat coverage often infrequent Different sun angles

9. Aerial photos: Film Types Black & White: panchromatic (Visible) Black & White Infrared: Near Infrared Color: Visible – Blue, Green, Red Color Infrared: Visible to Near Infrared

10. Primary Colors Red Green Blue

11. Subtractive Primary Colors Yellow (R+G) absence of blue Cyan (G+B) absence of red Magenta (R+B) absence of green

12. Color Additive Process R G B M Y C W Black background

13. YC M R G B B Color Subtractive Process White background

14. Color film Film Image colors GR Original colors YMC BGR Dye Layers B

15. Color Infrared film Original colors Film Image colors NIR Filter GR YMC BGR Dye Layers B

16. Fundamental Recognition Elements Shape Size Shadows - shape & height Tone/Color Texture Pattern Site Association

17. Photointerpretation: Recognition Elements Shape –cultural features - geometric, distinct boundaries –natural features - irregular shapes and boundaries –Shape helps us distinguish old vs. new subdivisions, some tree species, athletic fields, etc.

18. Photointerpretation: Recognition Elements Size –relative size is an important clue –apartments vs. houses –single lane road vs. multilane

19. Photointerpretation: Recognition Elements Shadows –shadows cast by some features can aid in their i.d. –some tree types, storage tanks, bridges can be identified in this way –shadows can also accentuate terrain Powerline transmission towers

20. Photointerpretation: Recognition Elements Color/Tone –irrigated vs. dry fields, coniferous vs. deciduous trees An algae bloom in colorAn algae bloom in CIR

22. Photointerpretation: Recognition Elements Texture –coarseness/smoothness caused by variability or uniformity of image tone or color –smoothness - surface features of similar height: crops, bare fields, water, etc. –coarseness - irregular surface: forest, lava flows Helyar Woods and points south

23. Photointerpretation: Recognition Elements Pattern –overall spatial form of related features –repeating simple geometric patterns tend to indicate cultural features –more complex, curving patterns tend to indicate natural features –drainage patterns can help geologists determine bedrock type A dendritic pattern is characteristic of flat-lying sedimentary bedrock

24. Photointerpretation: Recognition Elements Site –site - relationship of a feature to its environment/location –oak on hillside, Atlantic. white cedar in stream corridor Association –identifying one feature can help i.d. another - correlation –cooling towers, HT lines => power generating plant