immersed in, or at least touch, the objects of the observation and measurement Barett and Curtis, 1982.
Remote sensing is the technique of collecting information from a distance. By convention, “from distance” is generally considered to be large
relative to what a person can reach out and touch, hundreds of feet, hundred of miles, or more. Remote sensing techniques are used intensively to gather
measurements, satellite-based system can now measure phenomena that change continuously over time and cover large, often inaccessible areas
Aronoff, 1991. Remote sensing systems, deployed on satellite, provide a repetitive and
consistent view of the earth that is invaluable to monitoring the earth system and the effect of human activities on the earth Schowengerdt, 1997.
The major spectral regions used for earth remote sensing are shown in this table. These particular spectral regions are of interest because they contain
relatively transparent atmospheric “window”, through which barring clouds in the non-microwave regions the ground can be seen from above, and
because there are effective radiation detector in these regions.
2.3.1. Geometric Correction
Geometric correction that most often used to make digital remote sensor data truly useful is geometric rectification. Geometric rectification is
the processes of using Ground Control Points GCP’s are selected to transform the geometry of the images so that each pixel corresponds to a
position in a real world coordinate system. Rectification is the process by
7
which the geometry of an image area is made planimetric Haralicck, 1973 in Jensen, 1986.
2.3.2 Topographic Corrections
Besides geometric and radiometric error there are topographic mistakes caused by illumination differences and angle of earth surface
Smith and Brown, 1997. An area hit by a lot of sunshine will be seen brightness and on the contrary, although both of places have some cover
type. According to Jansa 1988, satellite image interpretation influenced
by shadow effect caused by relief of earth surface. Some factors have an effect in topographic error, such as Sun Azimuth angle, elevation, slope and
aspect of earth surface.
2.3.3 Remote Sensing Data
Each cover type on the earth has a specific characteristic to absorb, reflected and transmitted electromagnetic energy. Distinguished the fact
between an object and others on the earth’s surface and then can be using in the remote sensing technologies.
Remote sensing satellite record reflected and emitted radiant flux from earth surface object or materials. Difference reflected and emitted each
material are wavelength’s. The difference was used to know and interpreted what are materials or object on the earth’s surface.
8
2.3.4 Landsat Thematic Mapper TM
Landsat TM is a generation earth resources satellite, and combines reasonable spatial resolution cell size of 30 meters by 30 meters with the
reasonable range of spectral band 7 bands in visible and near, short and mid-infrared wavelengths Four detectors for the thermal-IR band provide
four scan lines on each active scan. The TM sensor has a spatial resolution of 30 meters for bands 1 through 5, and band 7, and a spatial resolution of
120 meters for band 6 Lillesand,1994. The thematic mapper spectral bands of Landsat - TM is shown in Table 2.1.
The Figure 2.1 below illustrates where in the EM spectrum the TM sensor can see. The rectangles depict the bandwidth recorded within that
region of the spectrum.
Figure 2.1. Electromagnetic Spectrum Lillesand and Kiefer, 2000 Landsat TM image is useful for image interpretation for much wider
range of application than Landsat MSS images. This is because the TM has both increases in number of spectral bands and an improvement in spatial
resolution as compared to MSS Lillesand, 1994
9
Landsat data are being used to support a wide range of applications in such areas as global change research, agriculture, forestry, geology,
resources management, geography, mapping, water quality, and oceanography. Landsat data have potential applications for monitoring the
conditions of the earth’s land surface. The landsat TM archive has over 300,000 scenes with a data volume of over 50 terabytes USGS, 1999.
Table 2.1 The Characteristics of Landsat Thematic Mapper TM Spectral Bands Lillesand and Kiefer, 2000.
Band Spectral Resolution
µm Nominal Spectral Location
Principal Application
1 0.45 - 0.52
Blue Provide increased penetration of water bodies, as well as
supporting analyses of land use, soil, and vegetation characteristics. The shorter-wavelength cutoff is just
below the peak transmittance of clear water, while the upper-wavelength cutoff is the limit of blue chlorophyll
absorption for healthy green vegetation. Atmospheric scattering and absorption substantially influenced
wavelengths below 0.45
µm 2
0.52 - 0.60 Green
This band spans the region between the blue and red chlorophyll absorption bands and therefore corresponds
to the green reflectance of healthy vegetation.
3 0.63 - 0.69
Red This is the red chlorophyll absorption band of healthy
green vegetation discrimination. It is also useful for soil- boundary delineations. This band may exhibit more
contrast than band 1 and 2 because of the reduced effect of atmospheric attenuation. The 0.69
µm cutoff is significant because it represents the beginning of a
spectral region from 0.68 to 0.75 µm, where vegetation
reflectance crossover take place that can reduce the accuracy of vegetation investigations.
4 0.76 - 1.90
Reflective Infrared The lower cutoff for this band was placed above 0.75
µm. this band is especially responsive to the amount of vegetation biomass present in a scene. It is useful for
crop identification and emphasizes soil crop and land water contrasts.
5 1.55 - 1.75
Mid Infrared This band is sensitive to the turgidity or amount of water
in plants. Such information is useful in crop drought studies and in plant vigor investigations. In addition, this
is one of the few bands that can be used to discriminate between clouds, snow and ice, which are so important in
hydrologic research.
10
Band Spectral Resolution
µm Nominal Spectral Location
Principal Application
6 10.04 - 12.5
Thermal infrared This band measures the amount of infrared radiant flux
emitted from surfaces. The apparent temperature is a function of the emissivities and the true or kinetic
temperature of the surface. It is useful for locating geothermal activity, thermal inertia mapping for geologic
investigations, vegetation classification, vegetation stress analysis, and soil moisture studies. The sensor often
captures unique information on differences in topographic aspect in mountainous areas.
7 2.08 - 2.35
Mid-infrared This is an important band for the discrimination of
geologic rock formations. It has been shown to be particularly effective in identifying zones of
hydrothermal alteration in rock.
2.3.5
Landsat-7 Enhance Thematic Mapper Plus ETM
+
Landsat 7 was officially integrated into NASA’s Earth Observing System EOS in 1994. It was launched on April 15, 1999 from Vandenburg
Air Force base, CA, using a Delta-II Expendable launch vehicle into a sun- synchronous orbit.
Landsat 7 provides a unique suite of high-resolution observations of the terrestrial environment. It was designed to achieve three main objectives
NASA, 1999:
Maintain data continuity by providing data that are consistent in terms of geometry, spatial resolution, calibration, coverage
characteristics, and spectral characteristics with previous landsat data;
Generate and periodically refresh a global archive of substantially cloud-free, sunlit landmass imagery; and
Continue to make landsat-type data available to U.S and international users at the cost of fulfilling user requests COFUR
11
and to expand the use of such data for global-change research and commercial purposes.
Landsat 7 is a three-axis stabilized platform carrying single nadir- pointing instrument, keeping the instrument pointed toward earth to within
0.05 degrees, and contains an improved Thematic Mapper sensor called the Enhanced Thematic Mapper ETM
+
. The ETM
+
instrument is a derivate of the Landsat 4 and 5 Thematic Mapper sensors Jensen, 2000.
Table 2.2. The Characteristics of Landsat 7 ETM
+
Lillesand And Kiefer, 2000.
Band Spectral Resolution µm
Spatial Resolution m at Nadir
1 0.450 - 0.515
30 x 30 2
0.525 - 0.605 30 x 30
3 0.630 - 0.690
30 x 30 4
0.750 - 0.900 30 x 30
5 1.55 - 1.75
30 x 30 6
10.40 - 12.50 60 x 60
7 2.08 - 2.35
30 x 30 8 pan
0.52 - 0.90 15 x 15
Table 2.3. The Characteristics Sensor of Landsat 7 ETM
+
Lillesand And Kiefer, 2000.
Sensor Technology Scanning Mirror Spectrometer
Swath Width 185 km FOV=15
o
Off-track viewing No
Data Rate 250 images per day 31,450 km
2
Revisit 16 days
Orbit and Inclination 705 km, sun-synchronous
Inclination= 98.2
o
Equatorial crossing 10:00a.m. + 15min Launch
April 15, 1999: 6 year duration 12
Landsat 7 has a 378-gigabit solid-state recorder that can hold 42 minutes of sensor data and 29 hours of housekeeping telemetry
data. This is necessary because the ETM
+
obtains 150 megabits of data each second. Landsat data production facilities have had to be
capable of handling very large quantities of data Barett and Curtis, 1982.
2.4 Classification
