Remote Sensing in an Hour
Geometry
Resolution
Objective
Wavelength
Signal
Geometry - ray path
•
Electromagnetic radiation
•
from source
•
to target
•
then sensor
Geometry - orbits
•
Swath width = f(altitude, semi-major axis)
•
azimuth = f(orbital inclination)
•
overlap, timing = f(orbital period)
Geometry NOAA
AVHRR
(Advanced Very
High Resolution
Radiometer)
Geometry Landsat
Geometry SPOT
Resolution
•
Distance between two distinguishable
objects
Resolution
•
Distance between two distinguishable
objects
Scale
scale = (width on image)/(width on Earth)
S = d/D
7 pixels wide
13 pixels wide
25 pixels wide
50 pixels wide
100 pixels wide
200 pixels wide
400 pixels wide
809 pixels wide
x
986 pixels high
= 797,674 pixels
= 2.3 Megabytes in JPEG format
2.3 by 3.2 inches
when printed at
300 dots per inch (DPI)
Trade-off
Fine resolution
(small pixels)
cover small area
(for given data volume)
Coarse resolution
(large pixels)
cover large area
(for given data volume)
30 meters per pixel
800 pixels wide
240 km wide
8000 pixels wide
http://www.ersc.wisc.edu/resources/resol.html
10 meters per pixel
800 pixels wide
80 km wide
8000 pixels wide
http://www.ersc.wisc.edu/resources/resol.html
5 meters per pixel
800 pixels wide
40 km wide
8000 pixels wide
http://www.ersc.wisc.edu/resources/resol.html
2 meters per pixel
800 pixels wide
16 km wide
8000 pixels wide
http://www.ersc.wisc.edu/resources/resol.html
1 meter per pixel
800 pixels wide
8 km wide
8000 pixels wide
http://www.ersc.wisc.edu/resources/resol.html
Trade-off
Fine resolution
(small pixels)
cover small area
(for given data volume)
Coarse resolution
(large pixels)
cover large area
(for given data volume)
Global Scale
Width on earth
= 20 thousand km = 2 x 107m
Width on screen (display)
= 2 meters
Scale = display/Earth
= 1 : 107 = one to ten million
Continental Scale
Width on screen (display)
= 2 meters
Width on earth
= 4 thousand km = 4 x 106m
Scale = Display/Earth
= 1: 2 x 106 = 1 to two million
Regional Scale
Width on screen (display)
= 2 meters
Width on Earth
= 1500 km = 1.5 x 106m
Scale = Display/Earth
= 1 : 7.5 x 105 = 1 to 750 thousand
sub-regional
scale
Width on screen (display)
= 2 meters
Width on earth
= 400 km = 4 x 105m
Scale = Display/Earth
= 1 : 2 x 105 = 1 to 200 thousand
Distances are order of magnitude
1m
10 m
100 m
1 km
10 km
100 km
1000 km
cars
buildings, big roads
rivers, football fields
towns
cities
Great Lakes
Rocky Mountains
County Scale
Width on screen (display)
= 2 meters
Width on earth
= 22 km = 2.2 x 104 m
Scale = Display/Earth
= 1:1 x 104 = 1:10 thousand
Local Scale
Width on screen (display)
= 2 meters
Width on earth
= 8 km = 8 x 103 m
Scale = Display/Earth
= 1 : 4 x 103 = 1 to 4 thousand
Detailed scale
Width on screen (display)
= 2 meters
Width on earth
= 2 km = 2 x 103 m
Scale = Display / Earth
= 1:1 x 103 = 1 to 1 thousand
Camp Randall
Stadium
Subset of an orthophoto made by
processing a mosaic of 79 photos taken
from an airplane in 1999 as part of the
UW Campus Map Project
http://www.ersc.wisc.edu
Ultra-detailed scale
Width on screen (display)
= 2 meters
Width on Earth
= 300 m
Scale = Display / Earth
= 1 : 150
Airphoto
Width on screen (display)
= 2 meters
Width on earth
= 200 m
Scale = display / earth
= 1 : 100
Enlarged air photo
Width on screen (display)
= 2 meters
Width on Earth
= 100 m
Scale = Display / Earth
= 1 : 50
Resolution
pixel size for panel (c)
D = d/S = (8 mm)/(1:4000) = 32 m
Objective: interpretation
• to transform data into information to guide decisions
Wavelength
wavelength = speed/frequency
λ = c/f
[m] = [m/s]/[1/s]
0.6 µm = (3E8 m/s)/(5E14 Hz)
(green)
Wavelengths
Signal
• what do you expect to see?
• what is wrong with this picture?
Flying
Car?
Same
location,
later
date
For alternative interpretations
http://www.theregister.co.uk/2006/01/25/flying_car_launch_site/
Eye in the Sky: Monitoring the
Earth by Satellite
Geology and Geophysics 118
1 credit
begins Tuesday March 25, 2008
Kurt Feigl, associate professor
feigl@wisc.edu
http://www.geology.wisc.edu/~feigl/118.html
Introduction to Remote Sensing
Environmental Studies 400
3 credits
begins September 2008
Annemarie Schneider, assistant professor
Practical Applications of GPS
Surveying
Geology and Geophysics 444
2 credits
begins Tuesday March 25, 2008
Kurt Feigl, associate professor
feigl@wisc.edu
http://www.geology.wisc.edu/~feigl/444.html