Insights
Glossary
Terms used across this site, defined without jargon.
Earth observation has an unusually dense vocabulary and a lot of it is unnecessary. These are the terms you will meet on this site and in our documentation.
| Term | Definition |
|---|---|
| Analysis-ready data (ARD) | Imagery that has been corrected for sensor, atmospheric and terrain effects so that measurements from different dates and sensors can be compared directly. |
| AOI | Area of interest. The geographic extent a customer subscribes to or tasks against. |
| Atmospheric correction | Removing the effect of the atmosphere from a measurement so that what remains describes the surface rather than the air above it. |
| Bundle adjustment | The simultaneous refinement of sensor position, orientation and scene geometry that makes accurate orthorectification possible. |
| CE90 / LE90 | Circular and linear error at 90% confidence — the standard way of stating horizontal and vertical positional accuracy. |
| Cess | The strip of ground alongside a railway track. Cess vegetation management is a core GRIDSCAN Rail function. |
| COG | Cloud-optimised GeoTIFF. A GeoTIFF organised so that a client can read part of it over HTTP without downloading the whole file. |
| Co-registration | Aligning two or more images so that the same ground feature falls on the same pixel in each. |
| Downlink | The transfer of data from a satellite to a ground station. Terravek's own downlink node is at Svalgrund. |
| Encroachment | Vegetation or third-party activity intruding into an infrastructure corridor's safety clearance. |
| FIELDKIT | Terravek's in-situ sensor node family. The ground half of ground truth. |
| Ground truth | Direct measurement on the ground used to calibrate or validate a remotely sensed estimate. |
| Hyperspectral | Imaging in many narrow, contiguous spectral bands — typically over a hundred — rather than a handful of broad ones. |
| InSAR / PSI | Interferometric SAR and persistent scatterer interferometry: techniques that measure millimetre-scale ground movement from radar phase. |
| ISO 19157 | The international standard for reporting geographic data quality. Every ORBIS delivery carries a conformant report. |
| ITRF2020 | The International Terrestrial Reference Frame realisation Terravek uses internally as its geodetic reference. |
| LiDAR | Light detection and ranging. A laser-based method of measuring distance, used to build point clouds and terrain models. |
| Orthorectification | Correcting an image for terrain and sensor geometry so that it has a consistent map scale throughout. |
| Radiometric calibration | Establishing the relationship between the digital number a sensor records and the physical radiance that produced it. |
| SAR | Synthetic aperture radar. An active sensor that works at night and through cloud, at the cost of a less intuitive image. |
| SDB | Satellite-derived bathymetry. A planning product, never a navigation product. |
| STAC | SpatioTemporal Asset Catalog. The open specification Terravek uses to publish imagery metadata. |
| Tasking | Requesting a new acquisition, as opposed to retrieving one from an archive. |
| Uncertainty budget | The itemised account of every source of error in a measurement and how they combine. |