Vineesh V, Geography

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...

 Digital Frame Cameras with Area Arrays in Satellite Remote Sensing What it is A digital frame camera is like a normal camera (phone or DSLR) but used in satellites. It takes a picture of the Earth in one shot (a frame), instead of scanning line by line. Area Array Sensor Inside the camera, there is an area array — a grid of tiny light-sensitive cells called pixels . Example: 4000 × 4000 pixels → captures a square image of the Earth. Each pixel records the amount of reflected light from the ground. How it works in satellites The satellite moves in orbit. The camera clicks frames at intervals . These frames are stitched together to create a large map of Earth's surface . Advantages High resolution → small ground details (like roads, fields, buildings) can be seen. Fast capture → takes a full area at once, not slowly scanning. Accurate geometry → less distortion compared to scanning sensors.

When an analyst looks at an aerial photo or satellite image, they rely on visual interpretation keys to identify features. These include size, shape, shadows, tone, texture, pattern, association, and site context . 1. Size Definition : The actual or relative dimensions of an object in the image. Concept : By knowing the scale of the photo , the real-world size of features can be estimated. Examples : An airport runway (large and long) vs. a village road (short and narrow). Comparing cars (small) with buses (larger). Fact : Size alone is not enough, but it helps eliminate confusion between features. 2. Shape Definition : The geometric form or outline of an object. Concept : Many cultural (man-made) features have regular shapes (rectangles, circles, straight lines), while natural features are often irregular . Examples : Rectangular → buildings, fields. Circular → water tanks, ponds, stadiums. Irregular → rivers, forests. ...

 Earth Resources Satellites These satellites are designed mainly for natural resource monitoring – land, water, vegetation, and environment. 1. LANDSAT (USA, since 1972) World's first dedicated Earth observation satellite series . Provides long-term continuous data for >50 years. Sensors : MSS (Multispectral Scanner), TM (Thematic Mapper), ETM+ (Enhanced TM), OLI (Operational Land Imager). Resolution : 15–30 m (optical). Applications : Land cover change, agriculture, forests, water resources. Fact : Landsat archive is the longest continuous Earth observation record . 2. SPOT (France, 1986 onwards) Name: Satellite Pour l'Observation de la Terre . Sensors : HRV (High Resolution Visible), HRVIR (with Infrared). Resolution : 1.5–20 m. Applications : Urban studies, vegetation monitoring, mapping. Fact : First civilian satellite to offer stereo imaging (3D views). 3. IRS (India, 1988 onwards) Name: Indian Remote Sensing...

Spatial Resolution 🗺️ Definition : The smallest size of an object on the ground that a sensor can detect. Measured as : The size of a pixel on the ground (in meters). Example : Landsat → 30 m (each pixel = 30 × 30 m on Earth). WorldView-3 → 0.31 m (very detailed, you can see cars). Fact : Higher spatial resolution = finer details, but smaller coverage. Spectral Resolution 🌈 Definition : The ability of a sensor to capture information in different parts (bands) of the electromagnetic spectrum . Measured as : The number and width of spectral bands. Types : Panchromatic (1 broad band, e.g., black & white image). Multispectral (several broad bands, e.g., Landsat with 7–13 bands). Hyperspectral (hundreds of very narrow bands, e.g., AVIRIS). Fact : Higher spectral resolution = better identification of materials (e.g., minerals, vegetation types). Radiometric Resolution 📊 Definition : The ability of a sensor to ...

In remote sensing, a platform is the physical structure or vehicle that carries a sensor (camera, scanner, radar, etc.) to observe and collect information about the Earth's surface. Platforms are classified mainly by their altitude and mobility : Ground-Based Platforms Definition : Sensors mounted on the Earth's surface or very close to it. Examples : Tripods, towers, ground vehicles, handheld instruments. Applications : Calibration and validation of satellite data Detailed local studies (e.g., soil properties, vegetation health, air quality) Strength : High spatial detail but limited coverage. Airborne Platforms Definition : Sensors carried by aircraft, balloons, or drones (UAVs). Altitude : A few hundred meters to ~20 km. Examples : Airplanes with multispectral scanners UAVs with high-resolution cameras or LiDAR High-altitude balloons (stratospheric platforms) Applications : Local-to-regional mapping ...

  Satellite remote sensing relies on detectors (sensors) that measure reflected/emitted electromagnetic radiation from the Earth. How sensors collect data depends on: Spectral coverage → Multispectral (few bands), Hyperspectral (hundreds), Thermal, Microwave. Detector type → Discrete detectors, linear arrays, or area arrays. Scanning mechanism → Scanning mirrors (whiskbroom) vs. linear arrays (pushbroom). Multispectral Imaging Using Discrete Detectors and Scanning Mirrors (Whiskbroom scanners) Principle : A single detector (or a few detectors) measures radiation one pixel at a time. A scanning mirror sweeps across-track (perpendicular to the satellite path) to build up the image line by line. The forward motion of the satellite provides the along-track dimension. Known as a whiskbroom scanner . Characteristics : Good calibration stability. Narrow instantaneous field of view (IFOV). Susceptible to mechanical wear (moving ...

Orbital characteristics of Remote sensing satellite geostationary and sun-synchronous  Orbits in Remote Sensing Orbit = the path a satellite follows around the Earth. The orbit determines what part of Earth the satellite can see , how often it revisits , and what applications it is good for . Remote sensing satellites mainly use two standard orbits : Geostationary Orbit (GEO) Sun-Synchronous Orbit (SSO)  Geostationary Satellites (GEO) Characteristics Altitude : ~35,786 km above the equator. Period : 24 hours → same as Earth's rotation. Orbit type : Circular, directly above the equator . Appears "stationary" over one fixed point on Earth. Concepts & Terminologies Geosynchronous = orbit period matches Earth's rotation (24h). Geostationary = special type of geosynchronous orbit directly above equator → looks fixed. Continuous coverage : Can monitor the same area all the time. Applications Weather...