Geographic phenomena fields objects boundaries.

In geography, geographic phenomena refer to features or processes that can be observed and studied on Earth's surface. These phenomena can be classified into three main categories: fields, objects, and boundaries. Each category has distinct characteristics, representations, and applications in Geographic Information Systems (GIS).

1. Fields

A field represents continuous, spatially varying data where a value is present at every location within the study area. It describes conditions that exist across a geographic area.

Characteristics:

Continuity: Fields have no discrete boundaries; the data is continuous.
Gradual Variability: The values of a field change gradually across space.
Representation: Typically modeled using raster data in GIS, where a grid structure assigns a value (e.g., temperature or elevation) to each cell.

Examples:

Temperature Map: Shows temperature variation across a region.
Rainfall Distribution: Displays rainfall levels over a large geographic area.
Elevation Data: Represents the height of land at every point in an area.

2. Objects

An object is a discrete geographic feature with a clearly defined location and boundaries. Objects are identifiable entities that exist as "whole" within a space.

Characteristics:

Discrete Entities: Objects are separate from their surroundings.
Defined Boundaries: Each object has clear limits.
Representation: Modeled using vector data in GIS, which represents objects as points, lines, or polygons.

Examples:

A City: Represented as a polygon or point on a map.
A River: Represented as a line feature in GIS.
A Building: Mapped as a point or polygon feature.

3. Boundaries

A boundary is the line or zone that marks the separation between different geographic features, fields, or phenomena. Boundaries can be sharp or gradual, natural or human-made.

Characteristics:

Sharp Boundaries: Distinct separation, such as a political border between two countries.
Gradual Transitions: Zones of change, such as a gradient from forest to grassland.
Representation: Typically represented as lines or polygons in GIS.

Examples:

Natural Boundary: Coastlines, rivers, or mountain ranges.
Human-Made Boundary: State or country borders, property lines.
Ecological Boundary: Transition zones between ecosystems, like a forest edge.

Key Differences Between Fields and Objects

Aspect	Fields	Objects
Nature	Continuous data across space	Discrete entities with defined boundaries
Representation	Raster data	Vector data
Examples	Temperature, elevation, rainfall	Cities, rivers, buildings
Change	Gradual changes across space	Fixed, defined locations

Fyugp note

GIS second semester

Comments

Platforms in Remote Sensing

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 ...

Types of Remote Sensing

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...

Resolution of Sensors in 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 ...

geostationary and sun-synchronous

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...

Optical Sensors in Remote Sensing

1. What Are Optical Sensors? Optical sensors are remote sensing instruments that detect solar radiation reflected or emitted from the Earth's surface in specific portions of the electromagnetic spectrum (EMS) . They mainly work in: Visible region (0.4–0.7 µm) Near-Infrared – NIR (0.7–1.3 µm) Shortwave Infrared – SWIR (1.3–3.0 µm) Thermal Infrared – TIR (8–14 µm) — emitted energy, not reflected Optical sensors capture spectral signatures of surface features. Each object reflects/absorbs energy differently, creating a unique spectral response pattern . a) Electromagnetic Spectrum (EMS) The continuous range of wavelengths. Optical sensing uses solar reflective bands and sometimes thermal bands . b) Spectral Signature The unique pattern of reflectance or absorbance of an object across wavelengths. Example: Vegetation reflects strongly in NIR Water absorbs strongly in NIR and SWIR (appears dark) c) Radiance and Reflectance Radi...

Vineesh V, Geography

Search This Blog