Remotesensing - introduction

REMOTE SENSING AND ITS APPLICATIONS

FCC HUBBALLI CITY – nov 2016

Remote Sensing

Weather forecasting

Google mapping

Remote sensing can be broadly defined as the collection and interpretation of information about an object, area, or event without being in physical contact with the object.

Aircraft and satellitesare the common platforms for remote sensing of the earth and its natural resources.

Aerial photography in the visible portion of the electromagnetic wavelength was the original form of remote sensing but technological developments has enabled the acquisition of information at other wavelengths including near infrared, thermal infrared and microwave.

Collection of information over a large numbers of wavelength bands is referred to as multispectral or hyperspectral data.Electromagnetic energy

The electromagnetic (EM) spectrum is the continuous range of electromagnetic radiation, extending from gamma rays (highest frequency & shortest wavelength) to radio waves (lowest frequency & longest wavelength) and including visible light.

The EM spectrum can be divided into seven different regions —— gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves.

Remote Sensing? Remote sensing is defined as the technique

of obtaining information about objects through the analysis of data collected by special instruments that are not in physical contact with the objects of investigation.

Collection of information about an object without coming into physical contact.

The information needs a physical carrier to travel from the objects/events to the sensors through an intervening medium.

The electromagnetic radiation is normally used as an information carrier in remote sensing.

The output of a remote sensing system is usually an image representing the scene being observed. 

The history of remote sensing began with the invention of photography. The term "photography" is derived from two Greek words meaning "light" (phos) and "writing" (graphien).

History

1858 Balloonist G.Tournachon made photographs of Paris from his balloon.

Systematic aerial photography developed for military and reconnaissance purposes beginning in World War I (1914 - 1918).

Artificial satellites in the latter half of the 20th century.

1038 AD – AL Hazen an Arabian mathematician explained the principle of the camera to observe sun eclipse.

1827 –’Niepce’ takes first picture of nature from a window view of the French countryside using a camera obscura and an emulsion using bitumen,

(it took 8 hours in bright sunlight to produce the image)

1858 - Gasper Felix Tournachon “Nadar" takes the first aerial photograph from a captive balloon from an altitude of 1,200 feet over Paris.

Elements involved in Remote sensing

1. Energy Source or Illumination (A)

2. Radiation and the Atmosphere (B)

3. Interaction with the Object (C)4. Recording of Energy by the

Sensor (D)5. Transmission, Reception and

Processing (E)6. Interpretation and Analysis (F)7. Application (G)

Remote Sensing Sensors

Active Remote Sensors :-

Active remote sensing uses an artificial source for energy.

For example the satellite itself can send a pulse of energy which can interact with the target.

In active remote sensing, humans can control the nature (wavelength, power, duration) of the source energy. Active remote sensing can be carried out during day and night and in all weather conditions.

Conti…

Passive remote sensing:-

Passive remote sensing depends on a natural source to provide energy.

For example sun is the most powerful and commonly used source of energy for passive remote sensing.

The satellite sensor in this case records primarily the radiation that is reflected from the target.

Types Passive Remote Sensing

Photography Radiometers Infrared

Active Remote Sensing RADAR is an acronym for "radio detection and ranging."

A radar system usually operates in the ultra-high-frequency (UHF) or microwave part of the radio-frequency (RF) spectrum, and is used to detect the position and/or movement of objects.

LIDAR, which stands for Light Detection and Ranging, is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth.

ACTIVE & PASSIVE REMOTE SENSING

Platforms

Platforms : The base on which remote

sensors are placed to acquire information about the Earth surface is called platforms.

• Ground based• Airborne• Space borne

•1934 - Photogrammetric Engineering first published. American Society of Photogrammetry founded and renamed Photogrammetric Engineering and Remote Sensing.  The Society was again renamed, and is now The American Society of Photogrammetry and Remote Sensing. •1946 - First space photographs from V-2 rockets.•1954 – U-2 takes first flight.•1957 - Russia launches Sputnik-1, this was unexpected and encouraged our government to make space exploration a priority.

Platforms used for Remote Sensing Ground-based platforms: ground, vehicles and/or towers => up

to 50 m

Airborne platforms: airplanes, helicopters, high-altitude aircrafts, balloons => up to 50 km

Space borne: rockets, satellites, shuttle => from about 100 km to 36000 km

1. Space shuttle: 250-300 km 2. Space station: 300-400 km 3. Low-level satellites: 700-1500 km 4. High-level satellites: about 36000 km

Techniques

Spectral Signatures

Image Acquisition

Spatial Resolution

Spectral Resolution

Multispectral Images

Radiometric Resolution

Spectral signature is the difference in the reflectance/emittance characteristics with respect to wavelengths (i.e., reflectance/emittance as a function of wavelength) is called as spectral signature.

The spectral signature of stars indicates the composition of the stellar atmosphere.

Spectral Signature

radiant energy that is measured by an aerial or satellite sensor

electromagnetic energy returned from the Earth’s surface can be detected by a light-sensitive film.

Image Acquisition

Spatial resolution is a term that refers to the number of pixels utilized in construction of a digital image. Images having higher spatial resolution are composed with a greater number of pixels than those of lower spatial resolution.

Spatial Resolution

High Resolutions Low Resolution

Multi Spectral Hyper Spectral:

Resolutions

Parallel sensor arrays detecting radiation in a small number of broad wavelength bands

allow discrimination of different types of :vegetation,

rocks and soils, clear and turbid water, and some man-made materials

Multispectral Images

Quantized incoming energy analyze the numerical values in the

bands of a multispectral image

Radiometric Resolution

RADAR System Radio Detection And Ranging Object detection system which uses

electromagnetic waves determine range, direction or speed

LiDAR System Light Detection And Ranging Measures distance by sending pulses of laser light

that strike and reflect from the surface of earth.

Advantages of remote sensing:-

Provides a regional view (large areas).

Provides repetitive looks at the same area.

Remote sensors "see" over a broader. portion of the spectrum than the human eye.

Provides geo-referenced, digital, data.

Some remote sensors operate in all seasons, at night, and in bad weather.

DISADVANTAGE OF REMOTE SENSING:- Expensive to build and operate Needs ground verification Not the best tool for small areas Needs expert system to extract data

Applications of Remote sensing

Meteorology Profiling of atmospheric temp. and water

vapor Measuring wind velocity

Oceanography Measurements of sea surface temperature Mapping ocean currents

Glaciology Mapping motion of sea ice and ice sheets Determining the navigability of the sea

Geology Identification of rock types Location of geological faults and anomalies

Applications of Remote sensing

AgricultureMonitoring the extend and type of vegetationMapping soil types

HydrologyAssessing water resourcesForecasting melt water run-off from snow

Disaster controlWarning of sand and dust storms, floodingMonitoring of pollution

Land Use Planning and Change

Passive sensors (Landsat, Terra, and SPOT satellites) are used in a broad range of forest and land use applications.

Landsat 7’s EMT+ sensor is especially useful in studying land use change because its data has been archived since the first Landsat mission in 1972.

Passive sensors have also been used to observe and monitor changes associated with storm, flood, and fire damage.

Metropolitan Kansas City region. This image is a "natural color" composite that simulates normal color appearance of the scene. The urban area is depicted in white (highways, buildings, railroads), muddy water is brown, and vegetated areas are shown in dark green. Compare with the standard false-color version (below) of this same scene. Landsat TM bands 1,2,3; acquired 3/83; image from NASA GSFC.

Kansas City metropolitan region. Standard false-color composite image formed from green, red, and short-infrared bands, color coded as blue, green, and red. Active vegetation appears red and pink, and water bodies are black. Urban structures appear in white to light blue shades.

Single-band, black-and-white image of southern Saskatchewan, Canada. Field of view about 150 km across. Short-infrared band depicts active vegetation in light gray tones; bare/fallow ground is dark gray; water bodies are black. 

The edge of the Andes Mountains is seen flanked by extensive alluvial fans that form relatively flat surfaces. Straight lines and geometric designs (left center) are the archeologic "Nazca lines" of prehistoric origin. This special composite employ visible and mid-infrared bands. Landsat TM bands 2,3,5; 

Infrared false-color composite of White Sands, New Mexico. The White Sands are dunes composed of gypsum sand blown from a nearby dry lake bed. In this image the gypsum dunes appear light blue, and the sand source area is dark blue. Landsat TM bands 4,5,7