Glossary

  • acquisition

    An image captured by a satellite sensor.

  • algorithm

    In the context of remote sensing, algorithms generally specify how to determine higher-level data products from lower-level source data. For example, algorithms prescribe how atmospheric temperature and moisture profiles are determined from a set of radiation observations originally sensed by satellite sounding instruments.

  • atmospheric correction

    Atmospheric correction is the process of removing the effects of the atmosphere on the reflectance values of images taken by satellite or airborne sensors.

  • band

    A discrete wavelength interval or range observed by a remote sensing instrument.  

  • collection

    ​​​​​​All products downstream of the rawest form of the main input data (telemetry), produced sequentially and processed with consistent algorithm/code/inputs/outputs

  • collection upgrade

    Reproduction of the collection, including all downstream products, with the initial input being the rawest form (telemetry)

  • Copernicus Australasia

    Copernicus Australasia is a regional hub supporting Copernicus, Europe's most ambitious and multifaceted Earth observation programme to date.

    The Copernicus Australasia Regional Data Hub provides free and open access to data from Europe's Sentinel satellite missions for the following South-East Asia and South Pacific region:

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    The hub is established under an agreement between Australia and the European Union. Implementation of the hub is facilitated by arrangements between the European Space Agency, the European Organisation for the Exploitation of Meteorological Satellites and Geoscience Australia. The project is operated collaboratively by Geoscience Australia, Queensland Department of Environment and Science, New South Wales Office of Environment and Heritage, Western Australian Land Information Authority and the Commonwealth Scientific Industrial Research Organisation. In 2018 New Zealand's Centre for Space Science Technology joined the consortium. The National Computational Infrastructure is contracted to implement and operate the master data repository.

    Operation of the regional data hub:

    • supports the business requirements of partner agencies;
    • forms a consolidated approach to enhance access to satellite Earth observation data for research, industry and civil society; and
    • fulfils a commitment to give back to the international satellite Earth observation community.
  • Copernicus Programme

    Copernicus is the European Union's Earth observation programme coordinated and managed by the European Commission in partnership with the European Space Agency (ESA), the EU Member States and EU Agencies. The Copernicus Programme was established in 2014, building on the previous EU's Earth monitoring initiative GMES.

    It aims at achieving a global, continuous, autonomous, high quality, wide range Earth observation capacity. Providing accurate, timely and easily accessible information to, among other things, improve the management of the environment, understand and mitigate the effects of climate change, and ensure civil security.

  • dataset

    A dataset is a related set of files composed of separate elements that can be manipulated as a unit. A dataset is an instantiation of a product.

  • dynamic range

    The range between the maximum and minimum amount of input radiant energy that an instrument can measure.

  • Enhanced Thematic Mapper Plus (ETM+)

    The sensor aboard Landsat 7 that picks up solar radiation reflected by or emitted from the Earth.

  • ephemeris

    A table of satellite orbital locations for specific time intervals. The ephemeris data help to characterize the conditions under which remotely sensed data are collected and are commonly used to correct the sensor data before analysis.

  • external product

    An external product is used to describe a product that was not generated by GA. These products will have fewer requirements in terms of information fields.

  • gain

     A general term used to denote an increase in signal power in transmission from one point to another; usually expressed in decibels. Can also be used to represent the multiplier used to transform from satellite image digital numbers to measures of at sensor radiance.

  • Landsat Program

    The Landsat Program is a series of Earth-observing satellite missions jointly managed by NASA and the U.S. Geological Survey.

    In a 1966 press release, Secretary of the Interior Stewart L. Udall, announced the start of “Project EROS”, a programed “aimed at gathering facts about the natural resources of the Earth from earth-observing satellites carrying sophisticated remote sensing observation instruments.” Secretary Udall named Dr. William T. Pecora, the Director of the U.S. Geological Survey, to lead the EROS program.

    In cooperation with NASA, on July 23, 1972, the Earth Resources Technology Satellite (ERTS-1) was launched. It was later renamed Landsat 1. Additional Landsat satellites followed in the 1970’s and 1980’s, and in 1999, Landsat 7 was launched. Landsat 8 (initially named Landsat Data Continuity Mission - LDCM) was the most recent satellite to be launched on February 11, 2013.  Landsat 9 is in development, with a launch scheduled for late 2020. 

    The instruments aboard the Landsat satellites have acquired millions of images through the course of the missions, and the data are a valuable resource for global change research and applications in agriculture, forestry, geology, regional planning, and education.

    Landsat data are received and downlinked to ground stations worldwide, and are archived at the USGS EROS Center in Sioux Falls, South Dakota. 

  • measurement

    A measurement is used to assign a number to a characteristic of an object or event, which can be compared with other objects or events.

  • Multispectral Scanner (MSS)

    A line-scanning instrument flown on Landsat satellites that continually scans the Earth in a 185 km (100 nautical miles) swath. On Landsats 1, 2, 4, and 5, the MSS had four spectral bands in the visible and near infrared with an IFOV of 80 meters. Landsat 3 had a fifth band in the thermal infrared with an IFOV of 240 meters. The MSS is a non-photographic imaging system that utilizes an oscillating mirror and fiber optic sensor array. The mirror sweeps from side to side, transmitting incoming energy to a detector array that sequentially outputs brightness values (signal strengths) for successive pixels, one swath at a time. The forward motion of the sensor platform carries the instrument to a position along its path where it can image an adjacent swath.

  • nadir

    The point of the celestial sphere that is directly opposite the zenith and vertically downward from the observer

  • near real time

    Time in which reporting on events or recording of events is performed as soon as practicable following an event. 

  • panchromatic

    sensitive to a wide range of wavelengths of light

  • pixel

    An abbreviation of picture element. The minimum size area on the ground detectable by a remote sensing device. The size varies depending on the type of sensor.

  • polar orbit

    An orbit with an orbital inclination of near 90 degrees where the satellite ground track will cross both polar regions once during each orbit. The term describes the near-polar orbits of spacecraft.

  • PostgreSQL

    PostgreSQL, often simply Postgres, is an open source object-relational database management system with an emphasis on extensibility and standards compliance. It can handle workloads ranging from small single-machine applications to large Internet-facing applications with many concurrent users

  • process

    A process describes the generation of some form of output as the result of a set of actions which may include sub-processes.

  • product

    A product is the term categorical term applied to describe the output from a process. Typically a product has an associated product definition which contains the product description and specification.

  • Python

    The programming language used to develop the Data Cube. It is easy to use while still allowing high performance access and processing capabilities. See http://www.python.org/ for more.

  • radiometer

     A device that detects and measures electromagnetic radiation

  • radiometric

    Relating to, using, or measured by a radiometer. The measurement of radiation.

  • raster data

    An abstraction of the real world where spatial data is expressed as a matrix of cells or pixels, with spatial position implicit in the ordering of the pixels. With the raster data model, spatial data is not continuous but divided into discrete units. This makes raster data particularly suitable for certain types of spatial operations (e.g., overlays or area calculations). Unlike vector data, there are no implicit topological relationships.

  • raw data

    Numerical values representing the direct observations output by a measuring instrument transmitted as a bit stream in the order they were obtained.

  • real time

    Time in which reporting on events or recording of events is simultaneous with the events. For example, the real time of a satellite is the time in which it simultaneously reports its environment as it encounters it.

  • reflectance

    The measure of the proportion of light or other radiation striking a surface which is reflected off it.

  • remote sensing

    In the broadest sense, the measurement or acquisition of information about some property of an object or phenomenon, by a recording device that is not in physical or intimate contact with the object or phenomenon under study. 

    Instruments that record characteristics of objects at a distance, sometimes forming an image by gathering, focusing, and recording reflected light from the Sun, or reflected radio waves emitted by the spacecraft.

  • resampling

    Modifying the geometry of an image (which may be from either a remotely sensed or map data source). This process usually involves rectification and/or registration.

  • resolution

    A measure of the amount of detail that can be seen in an image; the size of the smallest object recognizable using the detector.

    Intensity or rate of data sampling. In remotely sensed imagery, resolution is significant in four measurement dimensions: spectral, spatial, radiometric and temporal.

  • saturation

    The intensity of a color. A highly saturated color is a vivid, brilliant color; to dull a color (decrease its saturation), you add small amounts of its complement, making it closer to gray.

  • scenes

    Each Landsat image collected is a scene. Each Landsat scene is 115 x 106 miles long. The globe is divided into 57,784 scenes, and each Landsat scene has about 3 billion bytes of data.

  • spatial resolution

    The area on the ground that an imaging system (such as a satellite sensor) can distinguish.

  • spectral response

    The relative amplitude of the response of a detector vs. the frequency of incident electromagnetic radiation.

  • spectrometer

    An optical instrument that splits the light received from an object into its component wavelengths by means of a diffraction grating, then measuring the amplitudes of the individual wavelengths.

  • sun-synchronous orbit

    An orbit in which a satellite is always in the same position with respect to the rotating Earth at the same time of day. 

  • surface reflectance

    Surface reflectance is defined as the fraction of incoming solar radiation that is reflected from Earth's surface for specific incident or viewing cases (directional, conical, and hemispherical cases).

  • telemetry

    The science and technology of automatic measurement and transmission of data by wire, radio, or other means from remote sources, as from space vehicles, to receiving stations for recording and analysis.

  • Thematic Mapper

    "A Landsat multispectral scanner designed to acquire data to categorize the Earth's surface. Particular emphasis was placed on agricultural applications and identification of land use. The scanner continuously scans the surface of the Earth, simultaneously acquiring data in seven spectral channels. Overlaying two or more bands produces a false color image. The ground resolution of the six visible and shortwave bands of the Thematic Mapper is 30 meters, and the resolution of the thermal infrared band is 120 meters. Thematic mappers were flown on Landsat 4 and 5."

  • United States Geological Survey

    The USGS is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, and the natural hazards that threaten it.

  • Virtual Desktop Interface

    NCI’s Virtual Desktop Infrastructure (VDI) is an interactive environment for data visualisation and analysis in the cloud. The VDI substantially simplifies complicated analysis workflows that span multiple NCI systems by bringing together key data collections, analysis software, and compute systems in a familiar interface which users can work with as though on their own computer, without the need to wait on interactive queue jobs - http://nci.org.au/services/vdi/

  • wavelength

    The distance from crest to crest, or trough to trough, of an electromagnetic or other wave. Wavelengths are related to frequency: The longer the wavelength, the lower the frequency.

  • World Reference System

    A global indexing scheme designed for the Landsat Program based on nominal scene centers defined by path and row coordinates.

  • Xarray

    xarray (formerly xray) is an open source project and Python package that makes working with labelled multi-dimensional arrays simple, efficient, and fun

  • Yet Another Markup Language

    Originally YAML was said to mean Yet Another Markup Language, referencing its purpose as a markup language with the yet another construct, but it was then repurposed as YAML Ain't Markup Language, a recursive acronym, to distinguish its purpose as data-oriented, rather than document markup.

  • zenith

    The point on the celestial sphere directly above the observer. Opposite the nadir.