Vineesh V, Geography

Remote sensing, four basic radiation laws help us understand how objects give off and interact with energy (electromagnetic radiation). These laws link an object's temperature , wavelength , and the amount of energy it gives off: 1. Planck's Law Every object that has a temperature (above absolute zero) gives off energy at all wavelengths. But how much it gives off at each wavelength depends on its temperature. This law explains the full energy pattern (spectrum) of a hot object. 2. Stefan-Boltzmann Law Hotter objects give off more total energy. The energy released increases quickly as temperature rises — to the fourth power of the temperature. 3. Wien's Displacement Law Hotter objects give off energy at shorter wavelengths (like blue light), while cooler objects emit at longer wavelengths (like red or infrared). So, the color (or wavelength) of maximum emission shifts based on temperature. 4. Kirchhoff's Law If an object absorbs energy well at a cert...

Remote sensing is the science of collecting information about the Earth from a distance, usually using satellites or aircraft — without touching the surface.  Basic Principles of Remote Sensing Energy Source (Sun) ☀️ Everything starts with the Sun , which sends energy (light) to Earth. Interaction with Earth 🌳🏙️💧 This energy hits the Earth's surface — like forests, water, buildings — and gets: Reflected Absorbed Transmitted Sensors Detect the Energy 🛰️ Satellites or aircraft have sensors (cameras) that capture the reflected energy. Data Transmission 📡 The sensors send the collected data back to ground stations . Image Processing 💻 The raw data is processed into images or maps using computer software. Analysis 🧑‍💼 Scientists or analysts study the images to find out what's happening — like land use, vegetation health, urban growth, disasters, etc. Example: Imagine you're taking a photo of a city from an a...

1. Define the Purpose Decide why you're doing the mission: Mapping land use? Creating a 3D model? Surveying a building or farmland? 2. Choose the Area of Interest (AOI) Mark the exact area you want to cover on a map: Set boundaries (length & width) Use coordinates (lat/long) 3. Select the Camera and Drone Pick the right tools: Camera type (sensor size, resolution) Drone (range, stability, battery life) 4. Set Flight Parameters Plan how the drone should fly: Altitude (height) – affects image size and detail Overlap : Forward overlap (between photos in the same line) – usually 60-80% Side overlap (between photo rows) – usually 30-60% Speed – slow enough for clear photos 5. Calculate Flight Lines Create the path the drone will fly : Straight lines to cover the whole area Make sure the overlap is correct Consider wind and obstacles 6. Plan Ground Control Points (GCPs) Mark known ground...

In photogrammetry, aerial photographs are categorized based on camera orientation , coverage , and spectral sensitivity . Below is a breakdown of the major types: 1️⃣ Based on Camera Axis Orientation Type Description Key Feature Vertical Photo Taken with the camera axis pointing directly downward (within 3° of vertical). Used for maps and measurements Oblique Photo Taken with the camera axis tilted away from vertical. Covers more area but with distortions Low Oblique: Horizon not visible High Oblique: Horizon visible 2️⃣ Based on Number of Photos Taken Type Description Single Photo One image taken of an area Stereoscopic Pair Two overlapping photos for 3D viewing and depth analysis Strip or Mosaic Series of overlapping photos covering a long area, useful in mapping large regions 3️⃣ Based on Spectral Sensitivity Type Description Application Panchromatic Captures images in black and white General mapping Infrared (IR) Sensitive to infrared radiation Veget...

Photogrammetry is the science of making measurements from photographs, especially for mapping and surveying. When the camera axis is perpendicular (vertical) to the ground, the photo is called a vertical photograph , and its geometry is central to accurate mapping.  Elements of Vertical Photo Geometry In a vertical aerial photograph , the geometry is governed by the central projection principle. Here's how it works: 1. Principal Point (P) The point on the photo where the optical axis of the camera intersects the photo plane. It's the geometric center of the photo. 2. Nadir Point (N) The point on the ground directly below the camera at the time of exposure. Ideally, in a perfect vertical photo, the nadir and principal point coincide. 3. Photo Center (C) Usually coincides with the principal point in a vertical photo. 4. Ground Coordinates (X, Y, Z) Real-world (map) coordinates of objects photographed. 5. Flying Height (H) He...

Photogrammetry is the science of taking measurements from photographs —especially to create maps, models, or 3D images of objects, land, or buildings. Imagine you take two pictures of a mountain from slightly different angles. Photogrammetry uses those photos to figure out the shape, size, and position of the mountain—just like our eyes do when we see in 3D! Concepts and Terminologies 1. Photograph A picture captured by a camera , either from the ground (terrestrial) or from above (aerial or drone). 2. Stereo Pair Two overlapping photos taken from different angles. When seen together, they help create a 3D effect —just like how two human eyes work. 3. Overlap To get a 3D model, photos must overlap each other: Forward overlap : Between two photos in a flight line (usually 60–70%) Side overlap : Between adjacent flight lines (usually 30–40%) 4. Scale The ratio of the photo size to real-world size. Example: A 1:10,000 scale photo means 1 cm on the photo...

Raster Data Raster data is like a digital photo made up of small squares called cells or pixels . Each cell shows something about that spot — like how high it is (elevation), how hot it is (temperature), or what kind of land it is (forest, water, etc.). Think of it like a graph paper where each box is colored to show what's there. Key Points What's in the cell? Each cell stores information — for example, "water" or "forest." Where is the cell? The cell's location comes from its place in the grid (like row 3, column 5). We don't need to store its exact coordinates. How Do We Decide a Cell's Value? Sometimes, one cell covers more than one thing (like part forest and part water). To choose one value , we can: Center Point: Use whatever feature is in the middle. Most Area: Use the feature that takes up the most space in the cell. Most Important: Use the most important feature (like a road or well), even if it...

Every GIS analyst or geographer knows that behind every meaningful map lies a powerful story — and it all begins with raw spatial data . 1️⃣ Raw Geospatial Data Unstructured, scattered, and often layered with noise — from satellite imagery, GPS points, sensor feeds, or field surveys. Yet, this spatial data is the raw geography of the real world, waiting to be explored and interpreted. 2️⃣ Data Cleaning This is where geographic precision begins. Removing positional errors, correcting attribute inaccuracies, aligning projections — clean spatial data ensures accuracy in mapping and analysis. 3️⃣ Data Structuring Maps don't just happen. Behind every cartographic product is structured geospatial information: attribute tables, spatial relationships (topology), and layers that form the backbone of GIS. This step turns raw data into meaningful geographic databases. 4️⃣ Spatial Visualization Now, we map. Using GIS tools, spatial patterns emerge — land use maps, ch...

In GIS, a logical data model defines how data is structured and interrelated—independent of how it is physically stored or implemented. It serves as a blueprint for designing databases, focusing on the organization of entities, their attributes, and relationships, without tying them to a specific database technology. Key Features Abstraction : The logical model operates at an abstract level, emphasizing the conceptual structure of data rather than the technical details of storage or implementation. Entity-Attribute Relationships : It identifies key entities (objects or concepts) and their attributes (properties), as well as the logical relationships between them. Business Rules : Business logic is embedded in the model to enforce rules, constraints, and conditions that ensure data consistency and accuracy. Technology Independence : The logical model is platform-agnostic—it is not tied to any specific database system or storage format. Visual Representat...