Vineesh V, Geography

Remote Sensing means collecting information about the Earth's surface without touching it , usually using satellites, aircraft, or drones . There are different types of remote sensing based on the energy source and the wavelength region used. 🛰️ 1. Active Remote Sensing 📘 Concept: In active remote sensing , the sensor sends out its own energy (like a signal or pulse) to the Earth's surface. The sensor then records the reflected or backscattered energy that comes back from the surface. ⚙️ Key Terminology: Transmitter: sends energy (like a radar pulse or laser beam). Receiver: detects the energy that bounces back. Backscatter: energy that is reflected back to the sensor. 📊 Examples of Active Sensors: RADAR (Radio Detection and Ranging): Uses microwave signals to detect surface roughness, soil moisture, or ocean waves. LiDAR (Light Detection and Ranging): Uses laser light (near-infrared) to measure elevation, vegetation...

1. Foundational Phase (Early 1970s – Early 1980s) Objective: To explore the potential of space-based observation for national development. 1972: The Space Applications Programme (SAP) was initiated by the Indian Space Research Organisation (ISRO), focusing on applying space technology for societal benefits. 1975: The Department of Space (DoS) was established, providing an institutional base for space applications, including remote sensing. 1977: India began aerial and balloon-borne experiments to study Earth resources and assess how remote sensing data could aid in agriculture, forestry, and hydrology. 1978 (June 7): Bhaskara-I launched by the Soviet Union — India's first experimental Earth Observation satellite . Payloads: TV cameras (for land and ocean surface observation) and a Microwave Radiometer. Significance: Proved that satellite-based Earth observation was feasible for India's needs. 1981 (November 20): Bhaskara-II launche...

LiDAR (Light Detection and Ranging) is an active remote sensing technology that measures distances by illuminating a target with laser pulses and analyzing the time it takes for the reflected light to return. Unlike passive systems (e.g., cameras, multispectral sensors), LiDAR provides its own energy source (laser), allowing it to operate both day and night and even penetrate through vegetation canopies . 🔹 How LiDAR Works (Step-by-Step Process) Laser Pulse Emission The system emits rapid, short pulses of laser light (commonly in the near-infrared wavelength, 1064 nm ). Some systems emit up to hundreds of thousands of pulses per second . Interaction with Target Surface The laser beam strikes objects such as vegetation, buildings, or bare ground. Depending on the object's structure, part of the pulse may scatter or reflect. Return Signal Detection The sensor records multiple returns : First Return → typically vegetation canopy tops. ...

The Purvanchal Hills are an eastern extension of the Himalayan system , bending southward from Arunachal Pradesh along the Indo-Myanmar border. They include a series of discontinuous hill ranges such as the Patkai Bum, Naga Hills, Manipur Hills, Mizo (Lushai) Hills, Barail Range, and the Meghalaya Plateau (Khasi, Jaintia, and Garo Hills) . They are geologically young fold mountains (Tertiary period) made of sedimentary rocks (sandstone, shale, siltstone) . Their structure is the result of the collision of the Indian and Eurasian Plates , which uplifted the Himalayan orogeny . Unlike the snow-clad Greater Himalayas, these hills are moderate in elevation (600–3000 m) , with dense forests, heavy rainfall, and humid climate . 1. Barail Range Location: Separates the Brahmaputra Valley (north) and Barak Valley (south) in Assam. Geomorphology: Tertiary folded ranges with elongated ridges and valleys. Drainage: Acts as a watershed between the Barak River and the Brahma...

1. Principles Thermal Infrared Remote Sensing is based on the detection of naturally emitted electromagnetic radiation from objects, rather than reflected solar energy. According to Planck's Radiation Law , all objects with a temperature above absolute zero (0 K) emit electromagnetic radiation. For Earth surface features, the peak emission lies in the Thermal Infrared (TIR) region of 3–14 μm of the electromagnetic spectrum. The amount of radiation emitted is primarily a function of surface temperature and emissivity . Sensors measure the radiant energy flux density (W/m²) , which is later converted to surface temperature using Stefan-Boltzmann's Law . 2. Radiation Properties in TIR Emissivity (ε): Ratio of radiation emitted by a surface to that emitted by a perfect blackbody at the same temperature. Natural surfaces like water (ε ≈ 0.98) have high emissivity, while bare soils and metals have lower values. Blackbody: An idealized object th...

The Himalayas are a young fold mountain system , extending ~2,500 km from Nanga Parbat (west) to Namcha Barwa (east) , with a width of 150–400 km . Formed during the Tertiary period (~50 million years ago) by the collision of the Indian Plate and Eurasian Plate , they are still tectonically active. They act as a barrier to cold winds , a source of perennial rivers , a climatic divide , and a cultural-historical boundary between India and Central Asia. The system is divided into three longitudinal belts : Greater Himalaya (Himadri) Location : Northernmost and highest range, running continuously along the entire Himalayan arc. Elevation : 6,000–8,848 m; snow-covered throughout the year. Width : 25–40 km. Composition : Crystalline igneous rocks, gneisses, granites . Geological Origin : Formed from the Tethys Sea sediments uplifted by plate convergence. 🔹 Peaks Mount Everest (8,848.86 m) – highest peak in the world. Kanchenjunga, Nanga Parbat...

Determining the aerial photograph scale based on an aerial photograph and the measured ground size of objects Scale of an aerial photograph tells us how much the ground has been reduced to fit onto the photo. 👉 To find it, we need two things: The size of an object on the photograph (for example, a road or a building measured in centimeters on the photo). The real size of the same object on the ground (measured in meters or kilometers). Formula: Scale=Ground distance/Photo distance Example: A road measures 2 cm on the aerial photo. The real road length on the ground is 200 m (which is 20,000 cm). Scale = 2/20,000 = 1:10,000 So the scale of the photo is 1:10,000 , meaning 1 cm on the photo = 10,000 cm (100 m) on the ground . Measure on the photo. Measure the same on the ground. Divide photo size by ground size. Express as a ratio (1:n).

A natural disaster is a catastrophic event caused by natural processes of the Earth that results in significant loss of life, property, and environmental resources. It occurs when a hazard (potentially damaging physical event) interacts with a vulnerable population and leads to disruption of normal life . Key terms: Hazard → A potential natural event (e.g., cyclone, earthquake). Disaster → When the hazard causes widespread damage due to vulnerability. Risk → Probability of harmful consequences from interaction of hazard and vulnerability. Vulnerability → Degree to which a community or system is exposed and unable to cope with the hazard. Resilience → Ability of a system or society to recover from the disaster impact. 👉 Example: An earthquake in an uninhabited desert is a hazard , but not a disaster unless people or infrastructure are affected. Types Natural disasters can be classified into geophysical, hydrological, meteorological, clim...

  1. Location and Extent The Trans-Himalayas , also known as the Tibetan Himalayas , form the northernmost mountain system of India . Stretching in an east–west alignment , they run parallel to the Greater Himalayas , covering: Ladakh (Jammu & Kashmir, UT) Himachal Pradesh (north parts) Tibet (China) They mark the southern boundary of the Tibetan Plateau and act as a transition zone between the Indian Subcontinent and Central Asia . 2. Major Ranges within the Trans-Himalayas Karakoram Range World's second highest peak: K2 (8,611 m) . Contains Siachen Glacier and Baltoro Glacier . Geopolitical importance: forms part of India–Pakistan–China border. Ladakh Range Separates the Indus Valley from the Tibetan Plateau . Known for rugged barren mountains and cold desert conditions. Zanskar Range Lies south of the Ladakh Range, cut deeply by the Zanskar River . Famous for trekking and frozen river expeditions...

What it is These are cameras used by astronauts on spacecraft or space stations to take pictures of the Earth. Instead of automatic satellite sensors, here humans operate the camera . How it works Astronauts look through windows of the spacecraft. They use hand-held cameras (like high-quality film or digital cameras). They choose what to photograph → cities, mountains, rivers, clouds, disasters, etc. What is recorded The photos show visible light (what the human eye sees). Modern cameras can also use special lenses/filters for infrared or other wavelengths. Advantages Flexible → Astronauts can decide instantly what to capture. High resolution → Clear details because good cameras and lenses are used. Natural view → Looks like an ordinary photograph, easy to understand. Limitations Small coverage → Only parts of Earth, not continuous mapping like satellites. Depends on astronaut availability → Not always...