Fjärrsensing

Fjärrsensing, or remote sensing, is the science and practice of obtaining information about objects, areas, or phenomena from a distance, typically using aircraft or satellites. Sensors measure reflected or emitted electromagnetic radiation across visible, infrared, thermal, and microwave wavelengths. Remote sensing can be passive, detecting natural energy such as sunlight or thermal radiation, or active, emitting signals (such as radar or laser) and recording the return.

Data collected by fjärrsensing are processed into imagery or higher-level products. This processing includes radiometric and geometric calibration, atmospheric correction, and sometimes mosaicking or pan-sharpening. Data may be multispectral or hyperspectral, providing information across many bands that can be used to derive indices, classify land cover, or map materials.

Applications of fjärrsensing span many fields. It is used for land-use and land-cover mapping, agricultural monitoring (crop health and irrigation), forestry (biomass and disease detection), urban planning, water resource management, and environmental monitoring. It also supports disaster response, climate research, and archaeological investigations. Change detection and feature extraction are common analytical approaches, often integrated with geographic information systems (GIS).

Key technologies include optical and infrared cameras, hyperspectral imagers, synthetic aperture radar (SAR), and LiDAR. Platforms range from satellites and airplanes to unmanned aerial vehicles (drones) and ground-based sensors. Data sources include public satellites such as Landsat and Sentinel missions, as well as commercial and regional systems. While powerful, fjärrsensing faces challenges from weather and atmospheric conditions, resolution trade-offs, data volumes, and processing costs.