Remote sensing, types, applications

Remote sensing

Remote sensing is the collection of information about the Earth's surface without contact, by sensors on aircraft or satellites that record the electromagnetic energy reflected or emitted by objects.

Types

• Passive remote sensing: depends on the sun's energy (optical and thermal sensors, e.g. Landsat, Sentinel-2, aerial photographs).
• Active remote sensing: the sensor sends its own signal and records the return (radar, SAR, LiDAR).
• By platform: ground-based, airborne and spaceborne. By bands: panchromatic, multispectral, hyperspectral.

Applications in civil engineering

• Land use and land cover mapping: classification of urban, agricultural, forest and water areas from multispectral images.
• Route and site selection: alignment of roads, canals, pipelines and transmission lines, and choice of dam, bridge and airport sites using terrain, drainage and geology.
• Water resources: mapping of rivers, lakes and catchments; snow and glacier monitoring; flood extent and flood-plain mapping; watershed management.
• Geology and soil: identification of rock types, faults and lineaments, landslide-prone slopes and soil types for foundation and slope-stability studies.
• Disaster management: assessment of damage after earthquakes (e.g. Gorkha 2015), floods and landslides, and hazard mapping.
• Urban planning: monitoring of urban growth, infrastructure inventory, and change detection.
• Environmental monitoring: vegetation health, erosion, deforestation, pollution of water bodies, and impact assessment of projects.
• Construction and survey: DEM and contour generation, topographic mapping and quantity estimation.