What is Satellite Imagery?
What satellite imagery is, how it is captured, resolutions from 30 cm to 30 m and what each shows, archives back to 1972, and what it costs per km².
Summary
Satellite imagery is imagery of the Earth’s surface captured by sensors on orbiting satellites. Commercial systems resolve 30 cm to 10 m per pixel, revisit the same location daily to every few days, and hold archives reaching back decades: the free Landsat record starts in 1972 at 30 m, and commercial archive imagery is priced at roughly $2-55+ USD per km².
That is the short answer. The rest of this guide covers how the images are captured, what each resolution actually shows, the main imagery types, what industries do with it, and where the free data ends and the commercial data begins.
How Satellite Imagery Is Captured
A satellite image is not a photograph in the everyday sense. It is measured radiation, turned into a picture through a chain with four stages:
- Acquisition. Sensors on the satellite record energy from the Earth’s surface: reflected sunlight for optical sensors, emitted heat for thermal, or the echo of the satellite’s own radar pulse for SAR.
- Downlink. The data is transmitted to ground stations on the satellite’s next pass, or relayed in near real time.
- Processing. Raw data is corrected for sensor characteristics, atmosphere, and terrain-induced geometric distortion. Done fully, this chain is orthorectification, pansharpening, atmospheric correction, colour balancing and mosaicking; we’ve written up why that processing matters and what skipping it costs in accuracy.
- Analysis. The processed image goes into a GIS or analysis pipeline, where it becomes measurements: areas, volumes, vegetation indices, change maps.
The Landsat program, run by NASA and the USGS, has operated this loop continuously since 1972, which is why a 50-year time series of any place on Earth exists at 30 m resolution. Modern commercial constellations run it at far higher resolution and cadence: Maxar’s WorldView Legion satellites resolve 30 cm, and Geopera’s Perascope constellation delivers high-cadence sub-metre revisit through our exclusive access rights.
Resolution: What You Can Actually See
Resolution is the single spec that matters most, and the differences are concrete:
| Resolution | Example source | What a pixel shows |
|---|---|---|
| 30 cm | WorldView-3, Legion | Individual vehicles, fence lines, road markings |
| 50 cm | Perascope, SuperView | Buildings, site layouts, stockpiles |
| 1-2 m | Various archive sensors | Land parcels, large structures, clearings |
| 10 m (free) | Sentinel-2 | Field-scale vegetation patterns; buildings become blurs |
| 30 m (free) | Landsat | Regional land cover; a sports field is roughly one pixel |
Two other specs complete the picture. Revisit rate is how often a satellite can image the same spot: Sentinel-2 covers everywhere roughly every 5 days, and the large commercial constellations manage daily or better. Spectral bands determine what can be measured rather than merely seen: near-infrared and red edge bands drive vegetation analysis, and shortwave infrared supports mineral mapping.
The Main Types of Satellite Imagery
Optical imagery records reflected sunlight, in the visible bands and beyond. It is the most intuitive type to interpret and the workhorse for mapping and monitoring, with the limitation that clouds block it and it needs daylight.
Radar (SAR) imagery is built from the satellite’s own microwave pulses, so it works through cloud and at night. It reads as texture and structure rather than colour, and supports measurements optical cannot make, such as millimetre-scale ground deformation. Our SAR explainer covers how to read it.
Multispectral and hyperspectral imagery captures many narrow bands across the spectrum, from a handful (multispectral) to hundreds (hyperspectral), revealing properties like crop stress or mineralogy that RGB cannot. The difference between the two is mostly a trade between spectral detail and coverage.
Thermal sensors measure emitted heat, used for energy audits, volcanic monitoring and water temperature. Stereo collection captures the same area from two angles on one pass, which is how elevation models are built from satellites.
What Industries Do With It
The common thread is measurement over large or hard-to-reach areas, repeated on a schedule no ground survey can match.
Agriculture. Vegetation indices computed from multispectral bands flag crop stress before it is visible from the road; growers use them to target irrigation, fertiliser and inspection.
Mining. Exploration teams screen geology before fieldwork; operating mines monitor disturbance footprints, stockpiles and rehabilitation progress against regulatory commitments.
Environmental monitoring. Deforestation, coastal change, water quality and carbon-project baselines, tracked as time series across decades of archive.
Infrastructure and construction. Progress documentation with capture dates that stand up to a regulator or a dispute, plus corridor monitoring for pipelines and transmission lines.
Energy, insurance and government. Site selection for renewables, catastrophe damage assessment after storms and floods (radar working through the weather), and mapping programs at national scale.
The pattern across all of them: the imagery is the raw material, and the value arrives when it is processed well enough to measure from, which is why processing quality separates providers more than sensor lists do.
Free vs Commercial Satellite Imagery
A great deal of satellite imagery is free. Sentinel-2 (10 m, every ~5 days) and Landsat (30 m, since 1972) cover the whole planet, and our guide to the 10 free sources of satellite data covers where to get them. Free data genuinely answers regional-scale questions: land cover, broad vegetation trends, water extent.
Commercial imagery starts where pixels need to be smaller than a building. It runs roughly $2-55+ USD per km² depending on resolution and whether you buy archive or task a new capture; the full numbers are in our satellite imagery cost guide, and the process end to end is in how to buy satellite imagery.
Frequently Asked Questions
What is satellite imagery used for?
Measurement at scale: monitoring crops, mines, forests, coastlines and infrastructure; mapping; damage assessment after disasters; and documenting site conditions on a known date. Any task that needs a repeated, consistent view of a large or remote area is a satellite imagery task.
How is satellite imagery different from aerial imagery?
Aerial imagery is captured from aircraft at a few thousand metres and resolves 5-15 cm over campaign areas. Satellite imagery is captured from orbit at 30 cm to 30 m, covers anywhere on Earth without mobilising anything, and carries decades of archive. Our drone vs aerial vs satellite comparison maps which platform fits which job.
How often is satellite imagery updated?
It depends on the source. Free Sentinel-2 images everywhere roughly every 5 days; large commercial constellations revisit daily or better; and web basemaps like Google Earth are mosaics that may be months to years old. For a guaranteed fresh capture, imagery is tasked rather than pulled from archive.
How accurate is satellite imagery?
Resolution and positional accuracy are separate things. Commercial sensors resolve 30-50 cm per pixel, and after proper orthorectification positions are accurate to a few metres or better. Imagery without that correction can be displaced by tens of metres in terrain, which is why processing level matters when measurements face scrutiny.
Is satellite imagery free?
At 10-30 m resolution, yes: Sentinel-2 and Landsat are free and open. Sub-metre imagery is commercial, priced per km² of the area ordered, from about $2/km² for coarse archive to $55+/km² for 30 cm tasking.
