Satellite Imagery

Satellite imagery refers to images of Earth captured by sensors aboard orbiting satellites, providing synoptic views of the planet's surface at scales ranging from sub-meter to multi-kilometer resolution. Since the launch of the first Landsat satellite in 1972, satellite imagery has become one of the most important data sources for understanding and monitoring our planet. Modern Earth observation constellations such as Sentinel, Landsat, WorldView, and Planet LabsPlanet LabsPlanet Labs is a commercial satellite imagery provider that operates the largest constellation of Earth observation s... capture billions of images annually, creating an unprecedented record of how Earth's surface changes over time. Core ConceptsSatellite imagery encompasses several fundamental characteristics that determine its utility for different applications:Spatial resolutionSpatial ResolutionSpatial resolution defines the size of the smallest feature or ground area that can be distinguished in a spatial dat...: The size of the smallest feature that can be distinguished in an image, ranging from 30 centimeters for commercial high-resolution satellites to kilometers for weather satellites.Temporal resolutionTemporal ResolutionTemporal resolution is the revisit frequency of a satellite sensor over the same location on Earth, determining how o...: The frequency with which a satellite revisits the same location, ranging from daily revisits for large constellations to 16 days for individual satellites.Spectral resolutionSpectral ResolutionSpectral resolution describes the width and number of wavelength bands a remote sensing sensor can detect. Higher spe...: The number and width of wavelength bands captured by the sensor, from simple RGB cameras to multispectral and hyperspectral instruments.Radiometric resolutionRadiometric ResolutionRadiometric resolution is a sensor's ability to distinguish between different levels of electromagnetic energy intens...: The sensitivity of the sensor to differences in electromagnetic energy, typically expressed in bits per pixel.Swath widthSwath WidthSwath width is the ground strip width captured by a satellite or airborne sensor in a single pass. Wider swaths provi...: The width of the strip of Earth's surface captured in a single pass, which affects the trade-off between spatial resolution and coverage area. ApplicationsSatellite imagery supports an extraordinary range of applications across science, government, and industry:Environmental monitoringEnvironmental MonitoringEnvironmental Monitoring is the systematic collection and analysis of data about environmental conditions, including ...: Tracking deforestation, glacier retreat, coral reef health, and biodiversity loss through time-series analysis of satellite data.Agriculture: Precision farming applications use satellite imagery to monitor crop health, estimate yields, detect pest infestations, and optimize irrigation scheduling.Urban analysis: Mapping urban expansion, monitoring construction activity, assessing building density, and planning infrastructure using high-resolution satellite data.Climate science: Measuring sea surface temperatures, tracking ice sheet dynamics, monitoring atmospheric composition, and validating climate models.Disaster response: Rapid assessment of damage from hurricanes, earthquakes, floods, and wildfires using pre- and post-event satellite imagery.Defense and intelligence: Military and intelligence applications including surveillance, change detectionChange DetectionChange detection uses geospatial data and imagery to track and analyze alterations in landscapes, infrastructure, or ..., and situational awareness. AdvantagesSatellite imagery offers unique capabilities that complement other data collection methods:Global coverage: Satellites can image any location on Earth, including remote and inaccessible areas that are difficult to survey by other means.Consistent data collection: Orbital mechanics ensure regular, predictable revisit schedules, enabling systematic monitoring programs.Historical archive: Decades of archived imagery enable long-term trend analysis and historical baseline establishment.Non-intrusive observation: Data collection requires no ground access or physical presence, making it suitable for monitoring restricted or dangerous areas.Cost-effective at scale: While individual satellites are expensive, the cost per square kilometer of coverage is extremely low compared to aerial surveys. ChallengesSatellite imagery also presents certain limitations:Cloud cover: Optical satellites cannot see through clouds, which can severely limit data availability in tropical and frequently overcast regions.Resolution trade-offs: Higher spatial resolution typically comes at the cost of reduced coverage area and temporal frequency.Processing complexity: Raw satellite data requires significant preprocessing including atmospheric correctionAtmospheric CorrectionAtmospheric correction removes the effects of atmospheric scattering and absorption from satellite and aerial imagery..., georeferencingGeoreferencingGeoreferencing is the process of linking spatial data to specific geographic coordinates, enabling integration with o..., and radiometric calibrationRadiometric CalibrationRadiometric calibration converts raw digital numbers recorded by a sensor into physical units of radiance or reflecta....Cost of high-resolution data: While medium-resolution imagery from Landsat and Sentinel is free, very high-resolution commercial imagery can be expensive.Latency: Time between data capture and delivery can range from hours to days, limiting applications requiring truly real-time information. Emerging TrendsThe satellite imagery industry is experiencing rapid innovation:Small satellite constellations: Companies like Planet Labs operate constellations of hundreds of small satellites, providing daily global coverage at high resolution.AI-powered analysis: Machine learning and computer visionComputer VisionComputer Vision is a field of artificial intelligence that enables machines to interpret and understand visual inform... are automating the extraction of insights from massive volumes of satellite data.Analysis-ready data: Cloud platforms like Google Earth EngineGoogle Earth EngineGoogle Earth Engine is a cloud-based geospatial analysis platform that combines a multi-petabyte catalog of satellite... and Microsoft Planetary Computer provide preprocessed, analysis-ready satellite imagery at planetary scale.Synthetic aperture radar (SARSARSynthetic Aperture Radar (SAR) is an active remote sensing technology that uses microwave radar pulses to create high...): All-weather, day-and-night imaging capability is becoming increasingly accessible through missions like Sentinel-1 and commercial SAR constellations.Video from space: Some satellites now capture video footage of Earth's surface, enabling monitoring of dynamic events in near real-time. Satellite imagery has fundamentally transformed our ability to observe, understand, and manage Earth's surface and environment. As satellite technology continues to advance with smaller, cheaper, and more capable sensors, the volume, quality, and accessibility of satellite data will only increase, opening new possibilities for science, business, and governance.