LiDAR in Remote Sensing

LiDAR (Light Detection and Ranging) is an active remote sensing technology that uses laser pulses to measure distances to the Earth's surface and create high-resolution 3D maps.

LiDAR sensors emit short pulses of laser light (usually in the near-infrared range) and measure the time it takes for the pulse to return after hitting an object.

Because LiDAR measures distance very precisely, it is excellent for mapping:

terrain
vegetation height
buildings
forests
coastlines
flood plains

✅ 1. Active Sensor

LiDAR sends its own laser energy, unlike passive sensors that rely on sunlight.

✅ 2. Laser Pulse

LiDAR emits thousands of pulses per second (even millions).
Wavelengths commonly used:
- Near-Infrared (NIR) → land and vegetation mapping
- Green (532 nm) → water/ bathymetry (penetrates shallow water)

✅ 3. Time of Flight (TOF)

The sensor measures the time taken for the laser to travel:

from the sensor → to the surface → back to the sensor.

Distance is calculated using:

Distance = (Speed of light × Time) / 2

This gives the exact elevation of the surface.

✅ 4. Point Cloud

LiDAR produces millions of points with x, y, z values.

This collection is called a point cloud, which forms a precise 3D model of the area.

Each point includes:

location
height
intensity (strength of return)
classification (ground, vegetation, building)

✅ 5. Multiple Returns

A single laser pulse may hit:

the top of a tree
branches
the ground

LiDAR records multiple returns:

First return → top of canopy/building
Intermediate returns → branches, shrubs
Last return → ground surface

This allows:

canopy structure mapping
forest biomass estimation
accurate ground surface (DEM) generation

✅ 6. DEM, DSM, and DTM

LiDAR is excellent for generating elevation models:

DSM (Digital Surface Model): includes buildings, trees
DTM / DEM (Digital Terrain Model): bare ground level
nDSM: canopy height = DSM – DTM

✅ 7. LiDAR System Components

A typical LiDAR system includes:

Laser
Scanner / mirror
GPS (Global Positioning System) → position
IMU (Inertial Measurement Unit) → orientation
Receiver sensor

Together, they ensure high-accuracy 3D measurements.

Types

1. Airborne LiDAR

Mounted on aircraft or drones.
Used for:

topographic mapping
flood modeling
forest studies

2. Terrestrial LiDAR

Mounted on tripod/ground vehicles.
Used for:

building mapping
cultural heritage documentation
highways & mining

3. Bathymetric LiDAR

Uses green laser (532 nm) to penetrate water.
Used for:

river bed mapping
shallow coastal studies

Applications

🌲 Forest & Vegetation

canopy height
biomass estimation
forest structure analysis

⛰ Terrain Mapping

high-resolution DEM/DTM
landslide and fault mapping

🏙 Urban Studies

building heights
3D city models
urban planning

🌊 Hydrology and Flood Studies

floodplain mapping
drainage network extraction

🏛 Archaeology

detecting buried/hidden features
mapping ancient landscapes

🏞 Coastal & River Studies

shoreline change
bathymetry (water depth)

Comments

CREATION OF SPATIAL DATA

Spatial data creation is the process of generating, organizing, and managing geographically referenced information in a Geographic Information System (GIS). It involves converting maps, satellite images, GPS observations, and field survey data into digital datasets that can be stored, analyzed, and visualized. The quality of GIS analysis depends largely on the accuracy of spatial data creation. 1. Creation of Shapefile and Geodatabase A. Shapefile A Shapefile is one of the most widely used vector data formats developed by Esri for storing geographic features. Definition A shapefile stores the geometry and attributes of geographic features such as points, lines, and polygons. Components of a Shapefile A shapefile consists of several files: .shp – Stores geometry (shape) .shx – Shape index .dbf – Attribute table .prj – Coordinate Reference System (CRS) .sbn/.sbx – Spatial index (optional) Geometry Types Point – W...

Nature and Scope of Geography

Geography is the scientific study of the Earth's surface, its physical features, human populations, and the interactions between people and their environment. The word Geography is derived from the Greek words Geo (Earth) and Graphien (to describe or write), meaning "description of the Earth." Modern geography goes far beyond description; it seeks to explain where phenomena occur, why they occur there, how they are spatially distributed, and how they change over time. Geography is regarded as a spatial science , an environmental science , and an integrative discipline because it bridges natural sciences, social sciences, and geospatial technologies. Nature The nature of geography refers to the characteristics and fundamental features that define the discipline. 1. Geography as a Spatial Science Terminology: Spatial Science A discipline concerned with the location, distribution, arrangement, organization, and interaction of phenomena in ...

Geography of Health or Medical Geography

Health Geography (also known as Medical Geography ) is a sub-discipline of Human Geography that studies the relationships between place, environment, society, and health . It examines how spatial location, environmental conditions, and social and economic factors influence human health, disease patterns, and access to healthcare services. Health geography integrates concepts from geography, epidemiology, medicine, public health, environmental science, sociology, and Geographic Information Systems (GIS) to understand and improve population health. Major Components of Health Geography Health geography is generally divided into two major branches : The Geography of Disease and Ill Health The Geography of Health Care 1. The Geography of Disease and Ill Health This branch studies the spatial distribution, determinants, and diffusion of diseases across different geographical scales, from neighborhoods to global regions. It seeks t...

Historical Development of Geography in the Ancient Period

The Ancient Period marks the earliest stage in the evolution of geographical thought, extending from approximately 3000 BCE to the 5th century CE . During this period, geography evolved from simple descriptions of the Earth's surface to systematic scientific inquiry. Early civilizations developed geographical knowledge to meet practical needs such as navigation, trade, agriculture, military expansion, taxation, and administration . The greatest contributions came from the Mesopotamian, Egyptian, Indian, Chinese, Greek, and Roman civilizations , with the Greeks laying the foundations of scientific geography . Meaning Terminology: Historical Development Historical development refers to the gradual evolution of geographical knowledge, concepts, methods, and theories over time. Concept Geographical knowledge evolved through: Observation of the natural environment Exploration and travel Cartography (map-making) Astronomical observations ...

Development of Health Geography

Health Geography (formerly Medical Geography ) is the branch of geography that studies the relationship between health, disease, environment, place, and healthcare systems . The discipline has evolved over more than 2,500 years through contributions from physicians, geographers, epidemiologists, microbiologists, and public health experts. The development of Health Geography can be divided into the following periods: Ancient Period Medieval Period Renaissance and Pre-Modern Period Nineteenth Century (Pre-World War Era) World War Period Post-World War Period Modern Health Geography 1. Ancient Period (5th Century BC – 500 AD) Characteristics Health closely linked with the natural environment. Diseases explained through climate, water, air, and seasons. No knowledge of microorganisms. Medical observations were descriptive. Major Concepts Environmental Determinism Disease Ecology Climate and Healt...

Vineesh V, Geography

Search This Blog