WORDS THAT OPEN UP THE WORLD
The satellite glossary.
A plain-language reference for the ideas behind tracking, imagery, coordinates and visualization. Use it alongside the longer guides when a new term gets in the way.
- API
- An application programming interface: a defined way for software to request information or behavior from another component. The contract matters as much as the endpoint URL.
- Altitude
- A height relative to a stated reference. In the orbit explorer it is the distance above the model’s spherical Earth surface; the coordinate converter separately asks for ellipsoidal height.
- Coordinate frame
- The origin, axes and conventions that give a position meaning. A coordinate array without its frame can be easy to draw and difficult to interpret.
- ECEF
- Earth-centered, Earth-fixed coordinates. Their axes rotate with Earth; the coordinate tool reports x, y and z in meters using its stated WGS84 model.
- Epoch
- The reference time associated with a record or model state. Distinguish the source epoch from the time for which a position is calculated.
- GeoJSON
- A JSON format for geographic geometry and features. The converter exports a Point with longitude, latitude and height. See the developer guide for the coordinate convention.
- Geospatial data
- Information tied to a place or an area. Imagery, point features, boundaries and their metadata can all contribute to a geospatial workflow.
- GNSS
- Global navigation satellite system, a broader term for satellite navigation systems. GPS is one such system; a device’s location interface can use several kinds of input.
- Inclination
- The tilt of an orbital plane relative to its reference plane. The orbit explorer lets you change the modeled inclination relative to Earth’s equator.
- Latitude
- The north–south component of a geographic location, expressed as an angle. Be explicit about the reference model when converting it to a three-dimensional position.
- Longitude
- The east–west component of a geographic location, expressed relative to a reference meridian. It is the first coordinate in the GeoJSON points exported by this site.
- Metadata
- Information describing a dataset or asset, such as its identity, time, location, units, source and interpretation. It helps prevent a visually appealing layer from becoming misleading.
- Orbit
- The path of an object under the relevant forces. This site’s browser explorer uses a simplified circular model to make several orbital relationships easier to inspect.
- Orbital period
- The time required to complete a circuit in a stated model. The explorer reports its circular-model period in minutes alongside the selected altitude.
- OMM
- Orbit Mean-Elements Message. This term appears in orbital data exchange; consult the provider’s format documentation for the fields and serialization it actually supplies.
- Propagation
- Advancing a model from a known state or element set to another time. A propagated position is a model result, not automatically a new measurement.
- Raster
- A grid of values used to represent information such as imagery. The values, resolution and metadata determine what an image can meaningfully show.
- Reference datum
- A defined reference framework for coordinates. A visual overlay does not resolve differences between source datums; the integration needs a deliberate transformation.
- Remote sensing
- Gathering information about a subject from a distance. In this site, the discussion centers on Earth observation and the interpretation of imagery and related data.
- SGP4
- An orbital propagation model commonly encountered with general perturbations element data. The tracker guide links to the model and provider documentation for the correct pairing.
- STAC
- SpatioTemporal Asset Catalog, a specification used to describe and organize geospatial assets and their metadata. It helps connect discovery with the files and services behind a result.
- TLE
- Two-line element set, a compact orbital element format. The format is part of a modeling workflow; its values should not be treated as ordinary map coordinates.
- Vector data
- Features expressed through geometries such as points, lines and polygons. A vector boundary and a raster image can complement one another without having the same resolution or source.
- WGS84
- World Geodetic System 1984. The coordinate converter uses its ellipsoid parameters for Earth-centered conversion and labels its height input accordingly.