Introduction to Remote Sensing

• Remote sensing is collecting data at a distance from an object using a recording device.

Remote Sensing Definitions

• Remote sensing is acquiring information about an object without physical contact.
• It involves acquiring, processing, and interpreting images of electromagnetic energy and matter interactions.
• It is obtaining information about an object through data analysis from a device not in contact with the object.

History of Remote Sensing

• Remote sensing began in the 1840s using photographs from vantage points.
• Efforts were made to take pictures of the Earth using cameras on tethered balloons for topographic mapping.
• Simple remote sensing systems include binoculars and ordinary cameras.
• Cameras were used for military reconnaissance in the late 19th century.
• Aerial photography became important for mapping and planning from the late 1920s.
• Sonar and radar were developed during World War II.
• Various systems were developed for different types of electromagnetic radiation after World War II.
• 1783: The Marquis d'Arlandes and Pilatre made a voyage near Paris using a balloon, using photography with both balloons and pigeons.
• 1860: Aerial photos were taken in Russia and the USA.
• 1914-19: Photography saw tremendous development during the first and second World Wars.
• 1927: Robert Goddard launched the first liquid-fueled rocket.
• 1955: Work began on the Baikonur launch site in central Asia.
• 1957: Sputnik 1 was launched from Baikonur, becoming the first satellite.
• 1961: Yuri Gagarin was launched in the Vostok 1 capsule, becoming the first human in space.
• 1969: Neil Armstrong and Buzz Aldrin became the first humans to walk on the Moon.
• 1971: The Russian Salyut 1 was the first space station in history.
• 1972: The imaging concept from satellites was introduced with US Landsat1.
• 1986: France launched the first stereo-image satellite, SPOT1.
• 1992 was the maturity of remote sensing - 20 years of operation.
• 1995: The Shuttle-Mir Program was the 1st phase of the International Space Station (ISS).
• 2000: The first 3 astronauts lived in the ISS, with 2 Russians and one American.

Principles of Remote Sensing

• Remote sensing needs an energy source to illuminate or radiate electromagnetic energy to the target.
• The sun serves as a natural energy source in the form of EMR.
• As energy travels, it interacts with the atmosphere, especially when the energy sources is the sun.
• Energy interacts with the target based on the properties of both target and radiation.
• Some incident energy is reflected or emitted from the target after interacting with it.
• Reflected or emitted energy from the target interacts with the atmosphere again as it travels to the sensing or imaging device.
• After energy reflection by or emitted from the target, a sensor is needed to collect and record EMR.
• Recorded energy is transmitted, often electronically, to a ground receiving and processing station for image creation.
• Images are interpreted visually or electronically to extract information about the target.
• The information extracted from the imagery is applied to understand the target, reveal new information, or solve problems.

Types of Remote Sensing

• Passive remote sensing measures existing radiation, such as reflected solar radiation from the Earth.
• Active remote sensing emits radiation on the study object and measures the reflected amount of radiation.

Examples of Passive Remote Sensing

• Film Photography
• Infrared
• Charge-coupled device
• Radiometers

Examples of Active Remote Sensing

• RADAR
• LIDAR
• SONAR
• Eco-sounder

Platforms in Remote Sensing

• The base where are remote sensors are mounted is called a platform
• There are three platforms in the remote sensing process: Ground base, Atmosphere base, Space-based.
• Ground base platforms include tripod stands and hand-held cameras.
• They are used near the ground to develop and calibrate sensors for different features on Earth's surface.
• Atmosphere base platforms include balloons, helicopters, and airplanes.
• They allow both low and high altitude aerial remote sensing.
• Space-based platforms include rockets and satellites, such as space shuttles, polar orbiting satellites, and geo-stationary satellites.

Advantages of using aircrafts as a remote sensing platform

• High resolution data recording
• Possibility of carrying large payloads
• Cost effective imaging of large areas
• Accessibility of remote areas
• Convenience of selecting different scales
• Adequate control at all times

Elements of Image Interpretation

• Tone refers to the relative brightness or color of objects.
• Shape refers to the general form, structure, or outline of individual objects.
• Size of objects is a function of scale.
• Pattern refers to the spatial arrangement of discernible objects.
• Texture refers to the arrangement and frequency of tonal variation in particular areas.
• Shadow helps in interpretation by providing an idea of the profile and relative height.
• Association considers the relationship between recognizable objects in proximity to the target.

Applications of Remote Sensing

• Assessment and monitoring of vegetation types and their status
• Agricultural property management planning and crop yield assessment
• Soil surveys including mineral and petroleum exploration
• Monitoring and planning of water resources and groundwater exploration
• Urban planning
• Forest Resource Management
• Biodiversity Mapping
• Land use land cover