Conditions of Visuality
Conditions of Visuality explores how satellite observation systems translate orbital measurements into images. Each acquisition is selected by its temporal proximity to the requested moment and is constructed from the spectral bands chosen at left.
The project makes the systems, choices and conditions behind an orbital image visible: where the observation was requested, when the satellite passed, which instrument made the measurement and how the final composition was formed.
Sentinel-2 Overview
| Reference | Description | Specification |
|---|---|---|
| Observation System | ||
| Agency | European Space Agency (ESA) | |
| Programme | Copernicus | |
| Mission | Sentinel-2 | |
| Instrument | MSI (Multispectral Instrument) | |
| Orbit | Sun-synchronous low Earth orbit | Approx. 786 km altitude |
| Revisit Time | Time between passes over the same area | Approx. 5 days |
| Swath Width | Width of ground covered in one pass | 290 km |
| Satellites | ||
| Sentinel-2A | Satellite with the MSI instrument | Launched 23 June 2015 |
| Sentinel-2B | Satellite with the MSI instrument | Launched 7 March 2017 |
| Sentinel-2C | Satellite with the MSI instrument | Launched 5 September 2024 |
| Spectral Bands | ||
| B1, Coastal Aerosol | Deep blue, for coastal waters and aerosols | 60 m Spatial Resolution |
| B2, Blue | Visible blue | 10 m Spatial Resolution |
| B3, Green | Visible green | 10 m Spatial Resolution |
| B4, Red | Visible red | 10 m Spatial Resolution |
| B5, Red Edge 1 | Red edge, shorter wavelengths | 20 m Spatial Resolution |
| B6, Red Edge 2 | Red edge, intermediate wavelengths | 20 m Spatial Resolution |
| B7, Red Edge 3 | Red edge, longer wavelengths | 20 m Spatial Resolution |
| B8, NIR | Near-infrared | 10 m Spatial Resolution |
| B8A, Narrow NIR | Narrow near-infrared | 20 m Spatial Resolution |
| B9, Water Vapour | Absorbed by water vapour in the atmosphere | 60 m Spatial Resolution |
| B10, Cirrus | Detects high, thin cirrus clouds | 60 m Spatial Resolution (L1C only) |
| B11, SWIR 1 | Short-wave infrared | 20 m Spatial Resolution |
| B12, SWIR 2 | Longer short-wave infrared | 20 m Spatial Resolution |
| Processing Levels | ||
| L0 | Compressed raw data | Unavailable |
| L1A | Decompressed raw data | Unavailable |
| L1B | Calibrated radiance, not yet mapped onto the ground | Unavailable |
| L1C | Top-of-atmosphere reflectance, before atmospheric correction | Available |
| L2A | Surface reflectance, corrected for the atmosphere | Available |
Landsat Overview
| Reference | Description | Specification |
|---|---|---|
| Observation System | ||
| Agency | NASA / USGS (U.S. Geological Survey) | |
| Programme | Landsat | |
| Mission | Landsat 8 & Landsat 9 | |
| Instrument | OLI / OLI-2 (Operational Land Imager) | |
| Orbit | Sun-synchronous low Earth orbit | Approx. 705 km altitude |
| Revisit Time | Time between passes over the same area | Approx. 8 days |
| Swath Width | Width of ground covered in one pass | 185 km |
| Satellites | ||
| Landsat 8 | Satellite with the OLI instrument | Launched 11 February 2013 |
| Landsat 9 | Satellite with the OLI-2 instrument | Launched 27 September 2021 |
| Spectral Bands | ||
| B1, Coastal Aerosol | Deep blue, for coastal waters and aerosols | 30 m Spatial Resolution |
| B2, Blue | Visible blue | 30 m Spatial Resolution |
| B3, Green | Visible green | 30 m Spatial Resolution |
| B4, Red | Visible red | 30 m Spatial Resolution |
| B5, NIR | Near-infrared | 30 m Spatial Resolution |
| B6, SWIR 1 | Short-wave infrared | 30 m Spatial Resolution |
| B7, SWIR 2 | Longer short-wave infrared | 30 m Spatial Resolution |
| B8, Panchromatic | Broad visible band, at higher resolution | 15 m Spatial Resolution |
| B9, Cirrus | Detects high, thin cirrus clouds | 30 m Spatial Resolution |
| Processing Levels | ||
| Level-0 | Raw instrument data | Unavailable |
| Level-1 | Top-of-atmosphere reflectance, before atmospheric correction | Available |
| L1TP, corrected with ground control points and terrain | Level-1 Variant | |
| L1GT, corrected with terrain, without ground control points | Level-1 Variant | |
| L1GS, corrected with orbit data only | Level-1 Variant | |
| Level-2 | Surface reflectance, corrected for the atmosphere | Available |
| L2SP, surface reflectance and surface temperature | Level-2 Variant | |
| L2SR, surface reflectance only, without temperature | Level-2 Variant | |
| Level-3 | Derived products, such as burned area or snow cover (United States data only) | Unavailable |
Metadata
| Reference | Description | Specification |
|---|---|---|
| Observation System | ||
| Spacecraft | Satellite that captured the image | Sentinel-2A/B/C and Landsat 8/9 |
| Instrument | Sensor on board the satellite | MSI, OLI and OLI-2 |
| Spatial Resolution | Ground size of one pixel | Metres per pixel |
| Tile | Sentinel-2 grid square that contains the area | MGRS tile code (approx. 110x110 km) |
| WRS Path / Row | Landsat grid position of the area | WRS-2 path and row numbers (approx. 185x180 km) |
| Datatake | Sentinel-2 identifier of the continuous acquisition | Unique identifier |
| Product ID | Landsat identifier of the product | Unique identifier |
| Place and Time | ||
| Location | Point searched, contained inside the image shown | Latitude and longitude in degrees |
| Requested | Date searched | Date (UTC) |
| Acquisition | Moment the satellite captured the image | Date and time (UTC) |
| Product Generated | Moment the product was processed | Date and time (UTC) |
| Image Construction | ||
| Processing Level | Correction applied to the data (Landsat also shows the scene variant) | For example, L2A or Level-1 (L1TP) |
| Band | Bands shown in the RGB channels | Band, name and spatial resolution |