Short Answer:

Satellite images used in remote sensing are mainly classified based on how they capture data. The main types include optical images, thermal images, radar images, and hyperspectral images. These images help observe Earth’s surface for various purposes like land use, agriculture, water bodies, and environmental monitoring.

Each type of satellite image provides different information. Optical images use visible light, thermal images detect heat, radar images capture surface features through clouds, and hyperspectral images analyze many bands of light for detailed surface analysis. These images are useful in civil engineering, mapping, disaster management, and urban planning.

Detailed Explanation:

Types of satellite images used in remote sensing

Remote sensing involves collecting data about the Earth’s surface from satellites without direct contact. Satellite images are a key part of remote sensing. They provide valuable data for civil engineers, planners, and scientists to understand and monitor land features. Different types of satellite images are used based on the kind of data needed and the condition of the environment being observed.

There are four main types of satellite images used in remote sensing: optical images, thermal images, radar images (SAR), and hyperspectral images. Each has its own technique of capturing data and is suited for specific applications.

1. Optical Images (Multispectral):
   These are the most common type of satellite images. They use visible and near-infrared light to capture the Earth’s surface. Optical sensors divide light into multiple bands (colors), which helps in identifying vegetation, water bodies, urban areas, and soil.
   Example: Landsat satellites.
2. Thermal Images:
   Thermal sensors detect heat or infrared radiation emitted by surfaces. These images show temperature differences on the Earth’s surface and are used in heat mapping, forest fire detection, and studying urban heat islands.
   Example: MODIS thermal sensors.
3. Radar Images (SAR – Synthetic Aperture Radar):
   Radar satellites use microwave signals to capture surface images. They can work in all weather conditions, day or night, and even penetrate clouds and some vegetation. Radar images are used in flood mapping, topographic studies, and ground movement monitoring.
   Example: Sentinel-1, RISAT.
4. Hyperspectral Images:
   Hyperspectral sensors collect data in hundreds of narrow bands across the electromagnetic spectrum. These images provide detailed information about material composition on the surface and are used in mineral exploration, agriculture, and pollution studies.
   Example: Hyperion sensor.

Each type of satellite image plays a different role in civil engineering tasks like planning roads, monitoring land changes, managing natural disasters, and studying soil and water.

Conclusion:

In remote sensing, satellite images are chosen based on what kind of data is required. Optical, thermal, radar, and hyperspectral images each offer unique benefits for analyzing Earth’s surface. These images help engineers and planners make better decisions in land management, infrastructure development, and environmental protection.