What remote sensing means.
Remote sensing is collecting information about a place without touching it, usually by measuring energy reflected or emitted from the Earth’s surface. The sensor might sit on a satellite, an aircraft or a drone. A satellite image of your house, a drone survey of a roof and a radar map of a flood are all remote sensing data.
You will also hear Earth observation (often shortened to EO). It means much the same thing, with an emphasis on satellites observing the planet. Both terms describe how the data is collected; what you do with it afterwards is analysis.
NASA’s Earthdata introduction gives a good overview of the physics. Read NASA’s remote sensing basics.
Passive and active sensors.
Passive sensors record energy that comes from the scene itself. Optical cameras and multispectral sensors measure sunlight reflected by the ground, so they need daylight and a clear sky. Thermal sensors measure heat emitted by surfaces, which works by day or night.
Active sensors send their own signal and measure what returns. Radar, usually synthetic aperture radar (SAR), sends microwaves that pass through cloud. LiDAR sends laser pulses and times their return to measure height, often precisely enough to map the ground under trees.
Why it matters when you buy data: if your area is often cloudy, or you need an image during a storm, an optical satellite may not deliver in time. Radar or a drone flight under the cloud may be the better route.
Satellites, aircraft and drones.
The same kind of sensor can fly at very different heights, which changes how much area it covers and how much detail it sees.
- Satellites cover large areas and pass over regularly, so they build long archives. Commercial satellites see down to about 30 cm per pixel; free programs such as Sentinel-2 and Landsat provide 10 m and 30 m images.
- Crewed aircraft fly aerial photography and LiDAR surveys for regions and cities, often at a few to tens of centimeters per pixel. Many governments publish these surveys.
- Drones map a single site, roof or field at a few centimeters per pixel, on the day you choose, but cover small areas and need flight permissions.
For a side-by-side view of these options, see high-resolution satellite imagery and drone and aerial imagery.
Types of remote sensing data.
- Optical imagery: natural-color pictures of the ground, the kind most people mean by a satellite image.
- Multispectral imagery: several bands beyond what the eye sees, such as near-infrared, used for vegetation indices like NDVI.
- Hyperspectral imagery: hundreds of narrow bands that help tell materials and minerals apart.
- Thermal imagery: surface temperature, used for urban heat and heat loss.
- Radar (SAR): microwave images that work through cloud and at night, and InSAR measurements of ground movement.
- LiDAR and elevation: point clouds and terrain or surface models for contours, slope and height.
Each type answers different questions. The spectral and thermal, radar and LiDAR and elevation pages explain what each one is good for.
Four kinds of resolution.
Spatial resolution is the ground size of a pixel, such as 30 cm or 10 m. Temporal resolution is how often a place is observed. Spectral resolution is how many bands are recorded, and how narrow they are. Radiometric resolution is how finely each measurement is recorded, for example in 8 or 12 bits.
More detail is not always better: it costs more and covers less. Choose the detail your question needs. Read the resolution guide.
Remote sensing and GIS.
Remote sensing collects the data. A geographic information system (GIS) stores, combines and analyzes geographic data. A satellite image becomes a raster layer in a GIS, where you can overlay property boundaries, roads or field records, measure areas and compare dates.
You do not need to run GIS software yourself to use remote sensing data. You can buy the imagery on its own, or ask for an analysis such as change detection or an NDVI map. See how satellite image analysis works.
How to get remote sensing data.
Free data covers a lot: Sentinel-2 and Sentinel-1 through the Copernicus Browser, Landsat through USGS EarthExplorer, and national LiDAR and aerial programs in many countries.
Commercial data adds higher resolution, specific dates, new captures and licenses for business use. Drone and aerial surveys add centimeter detail for a single site.
Milkypad sources all of these for a place you choose and quotes the data before you order. See the satellite imagery and data you can buy, or read how to buy satellite imagery step by step.
Sources: NASA Earthdata, remote sensing; USGS, what is remote sensing and what is it used for? Checked 22 October 2026.