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1. PRESENTED BY
AGLAIA
Resolution and scanning system

2. Sensors
 They are devices used for making observations
 It consist of usually sophisticated lenses with filter
coatings to focus the area observed on a plane in
which the detectors are placed
 The major characteristics of imaging remote
sensing instrument operating in the visible and
infrared spectral bands are described in terms of
spatial ,spectral ,temporal and radiometric
resolution.

3. Spatial resolution
 A digital image consists of an array of pixels. Each
pixel contains information about a small area on the
land surface, which is considered as a single object.
 Spatial resolution is a measure of the area or size of
the smallest dimension on the Earth’s surface over
which an independent measurement can be made by
the sensor.
 It is expressed by the size of the pixel on the ground

5.  The size of the area viewed on the ground can be
obtained by multiplying the IFOV (in radians) by the
distance from the ground to the sensor. This area on
the ground is called the ground resolution or ground
resolution cell. It is also referred as the spatial
resolution of the remote sensing system.
 The IFOV is the angular cone of visibility of the
sensor, or the area on the Earth’s surface that is seen
at one particular moment of time.
 IFOV is dependent on the altitude of the sensor
above the ground level and the viewing angle of the
sensor.

6. IFOV variation with angle of view and altitude of
the sensor

7. Schematic representation of feature identification at different
spatial resolutions

8.  Based on the spatial resolution, satellite systems can be
classified as follows.
 Low resolution system
 Medium resolution systems
 High resolution systems
 Very high resolution systems
 Remote sensing systems with spatial resolution more
than 1km are generally considered as low resolution
systems.
Examples ;MODIS and AVHRR

9.  When the spatial resolution is 100m – 1km, such systems
are considered as moderate resolution systems.
Examples ; IRS WiFS (188m), LANDSAT TM (120m).
 Remote sensing systems with spatial resolution
approximately in the range 5-100m are classified as high
resolution systems. Examples LANDSAT ETM+ (30m), IRS
LISSIII (23m MSS and 6m Panchromatic) and AWiFS (56-
70m), SPOT 5(2.5-5m)
 Very high resolution systems are those which provide
less than 5m spatial resolution. Examples GeoEye (0.45m
for Panchromatic and 1.65m for MSS), IKONOS (0.8-1m

10. Spectral resolution
 Spectral resolution represents the spectral band width of
the filter and the sensitiveness of the detector.
 The spectral resolution may be defined as the ability of a
sensor to define fine wavelength intervals or the ability of
a sensor to resolve the energy received in a spectral
bandwidth to characterize different constituents of earth
surface.
 The finer the spectral resolution, the narrower the
wavelength range for a particular channel or band
 Generally surface features can be better distinguished
from multiple narrow bands, than from a single wide
band.

11. Hypothetical representation of remote sensing systems with
different spectral resolution

12.  In remote sensing, different features are identified
from the image by comparing their responses
over different distinct spectral bands.
 Broad classes, such as water and vegetation,
can be easily separated using very broad
wavelength ranges like visible and near-infrared.
 For more specific classes viz., vegetation type,
rock classification etc, much finer wavelength
ranges and hence finer spectral resolution are
required.

13.  Figure shows the difference in the spectral responses
of an area in different bands of the LANDSAT TM
image.

14. A coarse resolution
panchromatic image-
Minimum information is
visible from the image
LANDSAT TM (321)
showing forest fire in
Yellowstone NP- The
smoke cover
obstructs the ground
view

15. LANDSAT TM (754) showing forest fire in
Yellowstone NP

16. Temporal resolution
 It explains the revisting perioud of satellites
 Example; LANDSAT-16Days
MODIS-Daily

17. Radiometric resolution
 It depends upon the sensitivity of the sensor to
the magnitude of EMR.
 The finer the radiometric resolution of a sensor,
the more sensitive to detecting a small difference
in the reflected/ emitted energy.
 Data ,volume ,length increases as the radiometric
resolution increases.

18. Number of bits Maximum value
1 2
2 4
3 8
4 16
5 32
6 64
7 128
8 256
9 512
10 1024
11 2048

19. Multispectral imaging sensor
systems
 Many electronic (as opposed to photographic) remote
sensors acquire data using scanning systems, which
employ a sensor with a narrow field of view (i.e. IFOV) that
sweeps over the terrain to build up and produce a two-
dimensional image of the surface.
 A scanning system used to collect data over a variety of
different wavelength ranges is called a multispectral
scanner (MSS), and is the most commonly used scanning
system.

20.  There are two main modes or methods of scanning
employed to acquire multispectral image data -
across-track scanning, and along-track
scanning.
 Scanning systems can be used on both aircraft
and satellite platforms and have essentially the
same operating principles.

21. Along-track scanners
 It use the forward motion of the platform to record
successive scan lines and build up a two-dimensional
image, perpendicular to the flight direction.
 they use a linear array of detectors located at the focal
plane of the image formed by lens systems , which are
"pushed" along in the flight track direction (i.e. along
track).
 These systems are also referred to as pushbroom
scanners, as the motion of the detector array is

22.  Each individual detector measures the energy for a single
ground resolution cell (D) and thus the size and IFOV of
the detectors determines the spatial resolution of the
system.
 A separate linear array is required to measure each
spectral band or channel. For each scan line, the energy
detected by each detector of each linear array is sampled
electronically and digitally recorded.

23. Across-track scanners
 It scan the Earth in a series of lines. The lines are
oriented perpendicular to the direction of motion of the
sensor platform (i.e. across the swath).
 Each line is scanned from one side of the sensor to
the other, using a rotating mirror .
 As the platform moves forward over the Earth,
successive scans build up a two-dimensional image
of the Earth´s surface.

24.  The incoming reflected or emitted radiation is
separated into several spectral components that are
detected independently. The UV, visible, near-
infrared, and thermal radiation are dispersed into their
constituent wavelengths.
 A bank of internal detectors ,each sensitive to a
specific range of wavelengths, detects and measures
the energy for each spectral band and then, as an
electrical signal, they are converted to digital data and
recorded for subsequent computer processing.

26. Along track scanning system Across track scanning system

28. schematic diagram of narrow beam side scan sonar

29. THANK YOU
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