Data compression – For image archiving (satellite data) – For image transfer over internet

6.86 MB 15.2 MB Data compression

281 kb 673 kb Data compression

– Run-length codes Ex. # 1 Ex. # 2 Data compression

– Quadtree A quadtree recursively subdivides a plane into 4 quadrants If area is homogeneous, subdividing stops If the quadrant is heterogeneous with respect to this attribute, further subdivision occurs And so on, and so on, until….. Data compression

– Quadtree Data compression

– Quadtree Data compression 256 pixels down to to 80

vs. 160 (or so); run on polygon, not line Data compression – Quadtree

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NEXT: REMOTE SENSING BASICS 10

What is remote sensing? Collecting and interpreting information about a target without being in physical contact. ________ _______ is the medium of interaction. NOTE: We are not focusing on seismic or sonic remote sensing.

 Energy from the sun travels to Earth through space as electromagnetic radiation  The range of electromagnetic radiation is known as the electromagnetic spectrum radiation source

 Gamma rays<0.03 nm  X-rays0.03 – 300 nm  UV radiation0.30 – 0.38 μm  Visible light0.38 – 0.72 μm  Infrared Near-infrared0.72 – 1.30 μm Mid-infrared1.30 – 3.00 μm Far-infrared7.00 – 1,000 μm (1 mm)  Microwave1 mm – 30 cm  Radio ≥ 30 cm Image from: John R. Jensen Introduction to Remote Sensing, 2nd Edition. NJ: Pearson Prentice Hall.

Terms: Target Platform Sensor Designed to collect visible, IR, thermal... Instruments sense photons received at different wavelengths.

GOES 13 (East) GOES 15 (West)  Geostationary  Height = 22,237 miles  Speed = 0 mph  Orbital period = 24 hrs  Polar orbiting  Height = 438 miles  Speed = 16,800 mph  Orbital period = 99 min Landsat 7

 Passive RS: Uses natural energy Either reflected sunlight or emitted thermal or microwave radiation.  Active RS: Platform generates own energy Transmitted toward Earth, interacts with surface, reflects back toward sensor.

Landsat 7: 4, 3 (Las Vegas, NV area)Landsat TM: 4, 3, 2 (Rome, GA area)

Interferometric Synthetic Aperture Radar Mojave Desert, CA (National Training Center)

 Spatial  Spectral  Radiometric  Temporal

Reflectivity  m Visible Near IR Grass Concrete Maple Pine Asphalt High Low Water R B G

Normalized Difference Vegetation Index (NDVI)  Healthy chlorophyll pigments… ABSORB red (VISIBLE) REFLECT near infrared (NIR)  Unhealthy chlorophyll pigments -- stressed, diseased, yellowed, dead… REFLECT MORE visible REFLECT LESS near infrared (NIR) Band 4 (NIR) Band 3 (red) Large value means healthy

Earth systems science  Weather, climate, SST, dust, ash, geology Natural resource management  Agriculture, forestry, wildfires, fisheries, wildlife Social sciences  Land use/cover change, deforestation, flood plain mapping, urbanization, impervious surface mapping, archaeology, epidemiology, demography, pollution, urban heat islands, spying, before / after disasters LOOK AT ALL OF THESE NASA MISSIONS: 

 NOVA Landsat archaeology video - 14 min.