1. Characteristics of remote sensing systems

2. Different kinds of images
Panchromatic image
True-color image
False-color image

3. Panchromatic image
If airborne cameras use black/white film or satellite sensors use a single band, it produces panchromatic image (gray scale image)

4. Color composite Color primaries: RGB (Red, Green, Blue)
Many colors are formed by combining color primaries in various proportions
Same principles apply to producing color images taken from airborne cameras or satellite sensors

5. Greyscale vs. RGB Greyscale is typically used to display a single band
RGB (“Red”, “Green”, “Blue”) images can display 3 bands, corresponding to the red, green and blue phosphors on a monitor.

6. True color and false color images
True color image- the color of the image is the same as the color of the object imaged.
A false color image is one in which the R,G, and B values do not correspond to the true colors of red, green and blue. The most commonly seen false-color images display the very-near infrared as red, red as green, and green as blue.
For instance, different types of vegetation might appear as blue, red, green or yellow. Intuitively, vegetation would appear green.
Vegetation appear red in this color composite

7. Describing Sensors Spatial resolution Spectral resolution
Temporal resolution
Radiometric resolution

8. Spatial resolution
Spatial: pixel size; The size of the smallest possible feature that can be detected.
In a digital image, the resolution is limited by the pixel size, i.e. the smallest resolvable object cannot be smaller than the pixel size.
Fine or high resolution image refers to one with a small resolution size. Fine details can be seen in a high resolution image.
Coarse or low resolution image is one with a large resolution size, i.e. only coarse features can be observed in the image.
Aerial photo has higher resolution
The image resolution and pixel size are not equivalent.

9. Spatial resolution A low resolution MODIS scene (1km)
A very high resolution image acquired
by the IKONOS satellite (1m)

10. Spectral Resolution
The number, wavelength position and width of spectral bands a sensor has
A band is a region of the EMR to which a set of detectors are sensitive.
Multi-spectral sensors have a few, wide bands(several spectral bands)
Hyper-spectral sensors have a lot of narrow bands (hundreds of spectral bands)

11. Spectral Resolution
Multi-spectral
hyper-spectral

12. Radiometric resolution
The radiometric resolution of an imaging system describes its ability to discriminate very slight differences in energy (intensity level)
It depends on:
1- Radiance range-bits/pixel
2- Signal to noise ratio (S/N) of the detector. The ratio of the level of the signal carrying real information to that carrying spurious information as a result of defects in the system.

13. Radiometric Resolution
2-bit = 4 radiance levels
8-bit = 256 radiance levels
The finer the radiometric resolution of a sensor, the more sensitive it is to detecting small differences in reflected or emitted energy.

14. Temporal resolution
How frequent a given location on the earth surface can be imaged by imaging system.
For satellite image, it can be regular (satellites are orbiting the earth in regular time interval)

15. Earth Resource Satellites Operating in the Optical Spectrum
Landsat
SPOT
Meteorological Satellites
NOAA satellites
GOES satellites
Ocean Monitoring Satellites
Radar Satellites
Seasat
ERS-1
JERS-1
Radarsat

16. Introduction
Satellite systems operating within the optical spectrum ( m): UV, visible, near-, mid-, and thermal IR wavelengths
Landsat and SPOT
Higher resolution, contemporary programs (IKONOS, QuickBird)

17. Earth history of space imaging
Cameras on rockets (Germany 1891, 1907)
: beginning of space RS with small cameras aboard V-2 rockets (NM, USA)
Meteorological satellites (initial application) TIROS-1 (1960)
Corona, a military space imaging reconnaissance program ( ).

18. Earth history of space imaging
Manned space programs:
Mercury, Gemini, Apollo
Alan Shepard (1961): Made a 15-min suborbital Mercury flight on which 150 excellent photographs were taken
John Glenn (1962): Made 3 historic orbits around the earth and took 48 color photographs during Mercury mission MA-6
Gemini GT-4: geological application
Other geographic & oceanographic phenomena

19. Earth history of space imaging
Apollo 9: multispectral orbital photography for earth resource studies
1973: Skylab: Earth Resources Experiment Package (EREP)
1975: US-USSR Apollo-Soyuz Test Project (ASTP) hand-held cameras, disappointing results

20. Landsat Satellite Program Overview
Earth Resources Technology Satellites (ERTS) program (1967): a planned sequence of six satellites
In 1975, ERTS was renamed by NASA “Landsat”

21. Landsat Program
During the experimental Landsat phase, imagery was disseminated by Earth Resources Observation System (EROS) Data Center at Sioux Falls, SD.
Satellites were operated by NASA and USGS was handling the data distribution.

22. Landsat Program
Gradually, NOAA took over and the Landsat program operation was transferred to a commercial firm (Earth Observation Satellite Company – EOSAT).
Landsat-7 operation reverted to the government; EROS Data Center is the primary receiving station, processing and distributing the data.

23. Landsat Program
Landsat-1,-2,-3 images are catalogued according to their location within the Worldwide Reference System (WRS), by specifying:
a path (each orbit within a cycle)
a row (individual nominal sensor frame centers)
a date

24. Landsat Program

25. Landsat Program
E.g. the WRS has 251 paths for Landsat –1, -2,-3 (number of orbits to cover the Earth in 18 days).
Paths are numbered from 001 to 251, E to W, row 60 coincides with the equator.

26. ERTS-1 (Landsat-1) Launched by a rocket on 7/23/1972
Operated until 1/6/1978
The first unmanned satellite specifically designed to acquire data about earth resources on a systematic, repetitive, medium resolution, multispectral basis
43 US states & 36 countries

27. Landsat Satellite Program Overview
Landsats carried combinations of 5 types of sensors:
Return Beam Vidicon (RBV) camera systems
Multispectral Scanner (MSS) systems
Thematic Mapper (TM)
Enhanced Thematic Mapper (ETM)
Enhanced Thematic Mapper Plus (ETM+)

28. Landsat 1-3 orbital characteristics
Sun-synchronous orbits: The satellite crossed the equator at approximately the same local sun time (9:42) every day
Lunched into circular orbits at 900 km
Near-polar orbits travels northwards on one side of the earth and then toward the southern pole on the second half of its orbit, 14 times a day
Passing same point every (coverage repetition)
Sensors aboard imaged only 185 km swath
Globe coverage every 18 days (20 times/year)

29. Sensors Onboard Landsat-1,-2,-3
A three-channel Return Beam Vidicon (RBV) camera system
A four-channel MSS system

30. Return Beam Vidicon (RBV)
Nominal ground resolution of cameras: 80 m
Spectral sensitivity per camera: similar to a single layer of color infrared film (band 1: green ( ), band 2: red ( ), band 3: near IR ( )
Failed within weeks of Landsat 1

31. Landsat-3 Spectral sensitivity: green to near-IR
30 m nominal ground resolution

32. MSS System
The MSS onboard Landsat-1,-2,-3 covered a 185 km swath width in 4 wavelength bands (green, red, and 2 near-IR) designated as bands 4,5,6,7.
Note: In Landsat-4 and -5 they were bands 1,2,3,4.
On Landsat-3 there was a band 8 (thermal band) but this failed shortly after launch.

33. Orbit Characteristics of Landsat-4 & -5
In these missions, orbits were lowered from 900 to 705 km. This was done to aid in the improvement of the ground resolution of the sensors on board.
14.5 orbits/day (orbit period: 98.9 min)
16-day repeat cycle for each satellite (coverage cycle)
Local crossing at about 9:45 am.
Landsat-4 &-5 WRS: 233 paths ( , E-W), with 001 crossing the equator at 64°36’ W longitude
Same number of rows (60 coincides with the equator)

34. Sensors Onboard Landsat-4 & -5
MSS and TM sensors
MSS transmits 15 megabits/sec
TM transmits 85 megabits/sec
MSS data are collected using a 80-m ground resolution cell
MSS bands 1-4 in Landsat –4 & -5 corresponds to 4-7 of the Landsat–1,-2,-3

35. Sensors Onboard Landsat-4 & -5
MSS used a quantization range of 6 bits (64 digital numbers), but TM uses a range of 8 bits (256 numbers) for its onboard analog-to-digital signal conversion.
Finer radiometric precision Greater sensitivity to changes

36. Sensors Onboard Landsat-4 & -5
Thematic Mapper (TM)
TM: highly advanced sensor, improved over MSS
7 bands, ( μm)
TM data are collected using a 30-m ground resolution cell (thermal band: 120 m).
The size of area viewed on the ground is called the resolution cell
TM bands are more finely tuned for vegetation discrimination than those of MSS
TM Data are best for use in several application areas (bathymetry, rock type discrimination, etc.)

37. Landsat TM Vs. MSS
TM images cover a wider range of applications than Landsat MSS images, due to more spectral bands and improved spatial resolution.
MSS images are better for large area analyses (geologic mapping)

38. Landsat TM Vs. MSS
More specific mapping (detailed land cover) is difficult on MSS because many pixels are “mixed” pixels
TM’s decreased Instantaneous Field of view (IFOV) produces less mixed pixels
IFOV is the angular visibility of the sensor
Incorporation of mid-IR bands (5 & 7) has increased the vegetation discrimination of TM data

39. Landsat-6 Planned Mission
Launch failure on 10/5/93
Landsat-6 would have occupied an orbit identical to that of Landsat-4 & -5
The sensor of this mission was the Enhanced Thematic Mapper (ETM) (same bands, same resolution)

40. Landsat-6 Planned Mission
ETM’s major improvement over TM was the addition of an eighth “panchromatic” band with a spatial resolution of 15 m.
Another improvement was the use of a 9-bit analog-to-digital converter.

41. Landsat-7
This program is jointly managed by NASA and USGS (
Launched on April 15, 1999 (
A new sensor : Enhanced Thematic Mapper Plus (ETM+)
Same swath as ETM, similar orbits and characteristics
Swath: The area imaged on the surface.

42. ETM+ Resolution Complete global view four times a year
Bands1-5, 7: 30 meters
Band 6 (Thermal band): 60 meters
Band 8 (Panchromatic band): 15 meters
Complete global view four times a year

43. ETM+
Ground transmission of data either directly or stored onboard for later transmission
GPS is included for subsequent geometric processing of the data
Primary receiving station: EROS Dara Center, SD

44. ETM+ Spectral Bands

45. Landsat 7 +ETM Spectral Bands

46. Landsat Resources Data acquisition(

47. Enhanced Thematic Mapper Plus (ETM+)
8 8-bit bands: bands 1-7 are the same as TM; additional panchromatic band 8, μm
IFOV 30 x 30m (bands 1-5 and 7), 60 x 60m (band 6), 15 x 15m (band 8); swath width 185 km.
Images the earth once every 16 days; 1999 to present

48. Landsat MSS Image Interpretation
Scale & resolution differences between conventional aerial photos & Landsat images
Landsat imagery should be viewed as a complementary interpretive tool rather than a replacement for low altitude photography

49. Landsat MSS Image Interpretation
Most Landsat MSS images can only be studied in two dimensions
Effective resolution: 79 m
(30 m on Landsat-3 RBV)

50. Landsat MSS Image Interpretation
Due to the line scanning system (one-dimensional relief displacement), Landsat images can be viewed in stereo only in areas of sidelap on adjacent orbit passes.
Sidelap varies from 85% near the poles to 14% at the equator. Endlap is only 10%.

51. Landsat MSS Image Interpretation
Small vertical exaggeration when MSS images are viewed in stereo (extreme altitude vs. base distance between images)
Base to height ratio: 4x in stereo airphotos, 1.3x to 0.4x in Landsat MSS
Landsat MSS imagery has been used as a planimetric mapping tool

52. Landsat MSS Image Interpretation
The most appropriate band or combination of bands of MSS imagery should be selected for each interpretive use:
Bands 4 (green) & 5 (red) for detecting cultural features (5 provides higher contrast, 4 greater water penetration)
Bands 6 & 7 are best for delineating water bodies
Bands 5 & 7 are best for geologic studies (the largest single use of Landsat MSS data)

53. Landsat MSS Image Interpretation
Landsat satellite passes over the same area during daylight hours about 20 times/year.
Of course, the actual number of times/year a given ground area is imaged depends on the amount of cloud cover, sun angle, and whether the satellite is in operation on any specific pass.

54. Terra Spacecraft
Terra is the first of the NASA’s Earth Observing System satellite series. It was launched in December 1999 and activated for science operation on 24 February 2000.

55. Terra Instruments
ASTER: Advanced Spaceborne Thermal Emission and Reflection Radiometer
CERES: Clouds and Earth’s Radiant Energy System
MISR: Multi-Angle Imaging Spectro-Radiometer
MODIS: Moderate Resolution Imaging Spectrometer
MOPITT: Measurements of Pollution in the Troposphere

56. New Millennium Program
Earth Observing-1 (EO-1) is the first satellite in NASA's New Millennium Program Earth Observing series
EO-1 has validated a multispectral instrument that is a significant improvement over the Landsat 7 ETM+ instrument
EO-1 has validated a hyperspectral land imaging instrument and the unique science that can be performed with hyperspectral data
EO-1 has validated the ability of a low-spatial/high-spectral resolution imager that can correct systematic errors in the apparent surface reflectances caused by atmospheric effects, primarily water vapor.

57. Hyperion
The Hyperion is a high resolution hyperspectral imaging instrument
The Hyperion images the earth's surface in 220 contiguous spectral bands with high radiometric accuracy, covering the region from 400 nm to 2.5 µm, at a ground resolution of 30 m

58. Hyperion Sensor Characteristics
Spatial Resolution: 30 m
Swath Width: 7.75 km
Spectral Channels 220 unique channels. VNIR (70 channels, 356 nm nm), SWIR (172 channels, 852 nm nm)
Spectral Bandwidth 10 nm (nominal)
Digitization 12 bits
Signal-to-Noise Ratio (SNR) 161 (550 nm); 147 (700 nm); 110 (1125 nm); 40 (2125 nm)
Primary uses: General earth materials mapping geology, mining, forestry, agriculture, and environmental management

59. ALI (Advanced Land Imager)
The ALI instrument features 10-meter ground resolution in the panchromatic (black-and-white) band ( microns) and 30-meter ground resolution in its multispectral bands ( microns)
It covers seven of the eight bands of the current Landsat
It is designed to produce images directly comparable to Landsat 7 ETM+, will establish data continuity with previous Landsats

60. Comparison of Landsat-7 ETM+ and ALI spectral bands and spatial resolutions

61. AC (Atmospheric Corrector)
The AC instrument provides the first space-based test of an Atmospheric Corrector for increasing the accuracy of surface reflectance estimates.
The AC enables more precise predictive models to be constructed for remote sensing applications.
It will provide significant improvements in generating accurate reflectance measurements for land imaging missions.
It covers the micron wavelength IR band.

64. EO-1 Sensors Hyperion ALI (Advanced Land Imager)
AC (Atmospheric Corrector)

65. New Millennium Program
EOS Terra
ASTER
15 8-bit (VNIR and SWIR), 12-bit (TIR) bands: 4 VNIR (1 NIR off-nadir); 6 SWIR; 5 TIR
IFOV 15 x 15m (VNIR), 30 x 30m (SWIR), 90 x 90m (TIR); swath width 60 km.
Images are not acquired based on researcher scheduling; 1999 to present
MISR
4 VNIR bands at 9 different angles
IFOV 275 x 275 m to 1.1 x 1.1 km (depending on view angle); swath width 360 km.
9 day global coverage; 1999 to present

66. Terra Satellite MODIS ASTER (TIR) ASTER (SWIR) ASTER (VNIR) MISR
MOPITT
CERES

67. ASTER Characteristics
Wide Spectral Coverage
3 bands in VNIR (0.52 – 0.86 μm)
6 bands in SWIR (1.6 – 2.43 μm)
5 bands in TIR (8.125 – μm)
High Spatial Resolution
15m for VNIR bands
30m for SWIR bands
90m for TIR bands
Along-Track Stereo Capability
B/H 0.6
DEM Elevation accuracy:15m (3σ)
DEM Geolocation accuracy: 50m (3σ)

68. ASTER consists of 3 subsystems: VNIR, SWIR and TIR.

69. Comparison of Landsat-7 ETM+ and ALI Spectral Bands and Spatial Resolutions

73. Landsat 1-3 sensors Multispectral Scanner (MSS)
(green), (red), (near IR) at , m
resolution: 79 m (1-3), 82 m (4-5)
Each MSS scene is covering a 185 x 185 km area
Return Beam Vidicon Camera (RBV) - Landsat 1 and 2
m (green), m (red), m (near IR)
Failed within weeks of Landsat 1

74. Spectral sensitivity of MSS bands

75. Landsat 4-5 orbital characteristics
Altitude 705 km
Coverage cycle 16 days
Local crossing at about 9:45am
smaller sidelap (7.6% at the equator)

76. Sun-synchronous orbit of Landsat 4-5

77. Landsat 4-5 sensors Thematic Mapper (TM) launched with Landsat 4 and 5
7 bands, m
resolution: 30m except band 6 (thermal IR band, 120m)

78. TM spectral bands

79. Landsat 7 Launched on 15 April 1999 Orbit: very similar to Landsat 4-5
Sun-synchronous, polar
Altitude: 705 km
Repeat cycle: 16 days
Local crossing time: 10:00 am

80. Enhanced Thematic Mapper (ETM+)
Scene size
183 km cross-track
170 km along-track
Spectral Bands
8 bands: all TM bands + 1 panchromatic band
Resolution
Bands 1-5, 7: 30 metres
Band 6: 60 metres
Band 8: 15 metres