full of concepts about RS data acquisition scanning and imaging systems. Best for students of remote sensing. in this presentation we briefly explained the concept of scanning in remote sensing.
Remote Sensing Data Acquisition,Scanning/Imaging systems
1.
2. Group Members:
• Hussnain Tariq
• M Danyal Rustam
• Rahma Hassan
• Sibgha Saleem
• Amara Sattar
(8)
(9)
(14)
(25)
(26)
BS Semester 5th
Department of space science
University of the Punjab, Lahore
3. 1-RS Data Acquisition:
1.1 Parts of RS data acquisition
1.2 Types of Remote sensing Platforms
1.3 Types of Remote sensing Sensors
1.4 Difference between Photograph and Image
1.5 Scanning in RS
2- Data collection(scanning/imaging) Techniques :
2.1 Techniques for scanning(Along and Across Track scanning )
3. Types of Scanning/Imaging systems:
3.1 Passive imaging systems :
Multispectral,Hyperspectral and Thermal scanning/ imaging systems
3.2 Active imaging systems:
RADAR, LIDAR
Contents
5. 1-RS DATA ACQUISITION
Data Acquisition is the process of detecting signals that measure real world conditions
and converting the resulting samples into digital numeric values that can be manipulated
by a computer.
6. Platform:
The base/Carrier on which remote sensors are placed to acquire information
about the earth’s surface is called Platform e.g satellite, space shuttle, aircraft,
drone, helicopter, and balloon etc.
Sensor:
A sensor is a device that gathers energy and converts into the signals, then in
an image form, suitable for obtaining information about object under
investigation e.g Camera ,MSS, TM, ETM, ETM+, ASTER, MODIS, etc.
1.1 Parts of RS Data Acquisition:
7. 1.2 Types of Remote Sensing Platforms :
1: Ground level platforms:
o Very close to the ground
o Cranes, Hand-held
o Up to 50m
2: Aerial platforms:
o Low altitude
o High altitude
o Balloons , Drones , jet aircrafts
o Up to 50 km
3: Space borne platforms:
o Space shuttle
o Polar orbiting satellites
o Geo stationary satellites
o Up to 36000km
8. 1.3 Types of Remote Sensing Sensors:
(1) Active Sensors:
o Use an artificial source for energy.
o Can Work in both day and night in
all weather conditions.
Example:
LIDAR, Radar
(2) Passive sensors:
o Use a natural source of energy.
Example:
Sun
9. 1.5 Difference Between Photograph & Image
o Photograph is single click based.
o By developing a photograph we obtain a record of its detected
signals.
o The term photograph is reserved for images that were
detected as well as recorded on film
o Image is used for any pictorial representation of image data .
o Photograph is restricted to the visible and near-infrared regions.
o While Image is extended to thermal infrared.
10. o Scanning systems can be used on both aircraft and satellite
platforms and have essentially the same operating
principles.
1.6 Scanning in remote sensing
o Scanning is a process of sweeping over the terrain to build
up and produce a two-dimensional image of the surface.
o Scanner is a device that scans documents and converts
them into digital data.
12. 2.1 Techniques for scanning
There are two major methods of the scanning.
a)Across Track(Whiskbroom)
b)Along Track (push broom)
Example: SPOT and IKONOS
Example: Landsat
Along track scanning
Across track scanning
13. o It scan the earth in a series of lines having rotating mirror.
o The lines are perpendicular to the direction of motion of the
sensor platform i.e. across the swath.
o As the platform moves forward over the earth, successive
swath scans build up a 2-Dimensional image of the earth’s
surface.
o The distance from the sensor to the target increase towards
the edges of the swath, the ground resolution cells also
become larger and introduces geometric distortion to the
images.
Whiskbroom
a) Across Track
14. Instantaneous field of view(IFOV)
The cone angle β(IFOV) formula:
D / H = β
• Change in Viewing angle and Ground cell resolution
• Change in height and Ground cell resolution
16. Figure :Ground sampling distance concept
IFOV Instantaneous Field of View
GSD Ground Sampling Distance
Scanner’s ground resolution cell/element(IFOV
projected onto ground ) and system’s spatial resolution.
IFOV and GSD
17. Advantages Of Across Track Scanning
o It has fewer sensor detectors to keep calibrated as compared to other types of sensors.
o It has wide swath width.
o The Earth surface is scanned systematically line by line as it moves forward.
Disadvantages Of Across Track Scanning
o The moving parts make this type of sensor expensive.
o The moving mirrors create spatial distortions.
o This scanner has complex mechanical system than push broom scanner.
18. b) Along Track
o Also known as “Push broom scanning ”.
o Uses the forward motion of the platform to build
up a two dimensional image.
o It uses linear array of detectors oriented normal
to flight path.
o Records multispectral image data along a swath
beneath an aircraft.
o A complete line is recorded at a time.
20. Advantages of Along Track Scanning
o Linear array of detectors provides the opportunity to have longer dwell time(more
gathered energy ).
o Finer spatial and spectral resolution and Radiometric Resolution.
o Detectors last longer because they have no moving parts.
o Excellent geometrical properties.
o Each pixel has its own detector.
Disadvantages of Along Track Scanning
o Each spectral band requires it own linear array .
o Don't have a rotating mirror for varying angles.
22. 3.1 Types of Scanning/Imaging systems(Passive):-
In Remote Sensing we have following
types of the scanning systems.
1. Multispectral scanning/Imaging System
2. Hyperspectral scanning/Imaging System
3. Thermal scanning/Imaging System(emitted)
Hyperspectral image
Multispectral image
Thermal image
25. Radar (Radio detection and ranging):
• Detection system
• Uses radio waves
• Determine the range, angle, or velocity of objects
• Radio waves (pulsed or continuous) from the
transmitter reflect off the object and return to the
receiver, giving information about the object's
location and speed
RADAR IMAGING SYSTEM
26. Principle of Imaging Radar system:
The main system of an imaging radar
includes:
• Transmitter
• Receiver
• Antenna
• Recorder
Basic principle of the RadarRadar transmits a pulse Measures reflected echo (backscatter
28. Radar Images:
• Radar images are composed of
many dots, or picture elements.
• Radar is also an important source
of raster image data about the
Earth's surface
• ERS-1,ERS-2,Envisat,Sentinel-1
• JERS-1,Radarsat-1,Radarsat-2
Imaging different types of surface with radar
SIR-B image ,northern Florida
30. Advantages of Radar:
• All day free
• All weather free
• Used in both space and air
Disadvantages of Radar:
• It cannot resolve the type of the object.
• It cannot differentiate the color of the object
• It can be expensive if used in small areas especially if it is one time use
32. LIDAR (Light detection
and ranging system)
• Lidar technology is used to
provide elevation data.
• Lidar instrument consists of:
1. system controller
2. transmitter
3. receiver.
Elevation data points
(mass points)
Antenna
orientation
33. Digital Surface
Model (DSM)
• This Lidar derived digital
surface model is of UC Santa
Barbara.
• DEM is often used as a generic term for DSMs and
DTMs.
• DSM digitally represents elevation of all objects.
(ground + building)
• DTM digitally represents ground elevation of a
surface. (only ground)
35. Various displays of Last-Return LIDAR masspoints.
(a) Unedited
last-return
masspoints.
(b) IDW Digital
surface models
(DSM) overlaid with
masspoints.
(c) Shaded-relief of
IDW model overlaid
with masspoints.
(d) Unedited Last-
return masspoints
overlaid on
orthophoto.
36. LIDAR data of the Savannah River site
obtained on October 10,2004.
37.
38. RS Data Acquisition
Detection of electromagnetic energy.
• Sensors
• Platforms
Device for detection Sensor
Passive sensor Active sensor
• Hyper spectral
• Multispectral
• Thermal
• RADAR (Radio waves)
• LIDAR (Laser light)
39. References :
Wikipedia
From our syllabus(slides)
https://grindgis.com/remote-sensing/active-and-passive-remote-sensing
http://www.ni.com/data-acquisition/what-is/.
Data acquisition and integration 6., 6 Remote Sensing
Veronese Wojtaszek Malgorzata (2010). Nyugat-magyarországi Egyetem
Lillasand T. M.,Kiefer R. W.,Chip man W. J.:
Remote Sensing and Interpretation., John Wiley and Sons, Inc.,2007.
http://www.edc.uri.edu/nrs/classes/NRS409/RS/Lectures/HowRemoteSensonWork.pdf
Remote sensing of environment by Jensen
http://nature.berkeley.edu/~penggong/textbook/chapter3/html/home3.htm
http://www.slideshare.net/pabitramani/scanners-image-resolution-orbit-in-remote-
sensing-pk-mani
