Glossary of Terms

  • 9 August 2022
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The following table is a helpful reference that lists common Planet and industry terms with their acronyms and definitions.


Tip: Use the Find command to search for terms in this table. (Command+F for Mac or Control+F for PC).

Term

Acronym/ Abbreviation Definition 
1B image L1B Raw from space. A = minimal radiometric (color) correction, B = radiometric correction.
3A image L3A Rectified image. RapidEye: Radiometrically corrected, sensor corrected and band-aligned.
3B image L3B Orthorectified tile from an "image take."
Alpha Mask - An alpha mask is an image channel with binary values that can be used to render areas of the image product
transparent where no data is available.
Amazon Web Services AWS A collection of cloud based services.
Application Programming Interface API A way for two or more computer programs to communicate with each other.
Area of interest AOI Showing the location for analysis.
Area Under Management AUM Used to describe the total land area monitored and imaged by the satellite constellation.
Atmospheric Correction - The process of correcting at-sensor radiance imagery to account for effects related to the intervening
atmosphere between the earth’s surface and the satellite. Atmospheric correction has been shown to
significantly improve the accuracy of image classification.
Attitude Determination and Control System ADCS This is the name of the hardware and software systems onboard the satellite to measure and control its orientation, generally aiming to point straight down at the earth for imaging, point at a ground station for a pass, or point at the moon for focus adjustments.
Bandwidth BW

In computing, bandwidth is the maximum rate of data transfer across a given path. Bandwidth may be characterized as network bandwidth, data bandwidth, or digital bandwidth. add signal processing.

Blackfill - Non-imaged pixels or pixels outside of the buffered area of interest that are set to black. They may appear as
pixels with a value of “0” or as “noData” depending on the viewing software.
Bias - General term for a constant, added-in amount of signal, independent of the amount of signal present. Analogous to the y-intercept of a line (as opposed to its slope).
Bucket - Our interface which abstracts (currently s3) storage of large items. Multiple scenes can be stored in one bucket.
Camera model - A math model describing how to relate images taken with different camera settings, temperature, etc - the camera model lets us transform images into a comparible form no matter how they were acquired.
Capture - Same as 'Collect: The full tuning fork, which is a combination of all frames collected for a single SkySat order."
Clear Cut - Complete removal of trees in harvest area.
Collect - The full tuning fork, which is a combination of all frames collected for a single SkySat order.
Concept of Operations CONOPS A verbal or graphic statement of a commander's assumptions or intent in regard to an operation or series of operations.
Digital Elevation Model DEM A digital elevation model (DEM) is a 3D computer graphics representation of elevation data to represent terrain, commonly of a planet, moon, or asteroid. DEMs are used often in geographic information systems, and are the most common basis for digitally produced relief maps.
Digital Numbers DN Values for pixels in a scene.
Digital Surface Model DSM A digital surface model (DSM) is a 3D computer graphics representation of surface data to represent elevation and terrain.
Elastic Compute Cloud EC2 An Amazon Web Services service allowing users to launch virtualized hardware servers on demand.
European Space Agency ESA Europe’s gateway to space. Its mission is to shape the development of Europe’s space capability and ensure that investment in space continues to deliver benefits to the citizens of Europe and the world.
Field Of View FOV The field of view is the extent of the observable world that is seen at any given moment. In the case of optical instruments or sensors it is a solid angle through which a detector is sensitive to electromagnetic radiation.
Flock 2k F2K Represents the 11th Flock of Dove Earth-Observation CubeSats to reach the launch pad
Flock 2p F2P Represents the 12th Flock of Dove Earth-Observation CubeSats to reach the launch pad
Flock 3p F3P Represents the 10th Flock of Dove Earth-Observation CubeSats to reach the launch pad
Fork / Tuning Fork - Same as Collect: The full tuning fork, which is a combination of all frames collected for a single SkySat order. Descriptive of the shape of an image captured with current SkySat Concept of Operations (CONOPS)
Frame - The smallest increment of an image, captured on-board the spacecraft at up to 50 fps (frames per second, also communicated as hertz).
GeoJSON - A standard for encoding geospatial data using JSON
Geospatial Data Abstraction Software Library GDAL A library (and set of commandline tools) for reading/writing and manipulating geospatial raster/vector data.
GeoTIFF - A JSON based format for geospatial geometries (polygons, etc).
Google Cloud Platform GCP Where product infrastructure & services run.
Graphical User Interface (GUI) - Web based interfaces enable users to interact with Planet's imagery products without needing knowledge of
how to use APIs or Application Programming Interfaces.
Ground Control Point GCP A location in an image with a known real-world location.
Geographic Information System GIS A computer system that analyzes and displays geographically referenced information.
Google Earth Engine GEE This platform combines a multi-petabyte catalog of satellite imagery and geospatial datasets with planetary-scale analysis capabilities.
Grid - The system of breaking down the world into smaller pieces.
Examples: RapidEye grid, Universal Transverse Mercator (UTM) grid, various MGRS grids.
Grid Cells - One of the positions in a grid. At BlackBridge and in the RapidEye metadata, these are known as tiles and each has a unique ID number.
In the RapidEye grid, each cell is 25x25km.
In the case of UTM, each cell is measured in degrees, so they have variable sizes.
Ground Resolved Distance GRD The size of the smallest (subjectively) resolvable object in a given image.
Ground Sample Distance GSD In remote sensing a digital photo (such as an orthophoto) of the ground from air or space is the distance between pixel centers measured on the ground.
Heatmap - A way to show data represented by colors. 
Image - The full tuning fork, which is a combination of all frames collected for a single SkySat order.
Image Take IT The full 5-band image taken by a single satellite. With RapidEye imagery, they are 12000 pixels wide (with the first and last 10 pixels unusable), with varying length (up to 46154 lines in length).
Image Take Tile ITT The tile within an image take that corresponds to a tile in the tile grid. These tiles are cataloged.
JavaScript Object Notation JSON Text-based data interchange format used by the Planet API.
Landsat 8 - Freely available dataset offered through NASA and the United States Geological Survey
Map Tile or Web Tile - JPEG or PNG versions of ortho tiles that are used in web mapping.
Note: The Platform team prefers map tile but the industry standard is web tile. Planet's web tiles are 256x256 pixels in size and come at various zoom levels. They do not align to the grid cells of ortho tiles.
Metadata - Data delivered with Planet’s imagery products that describes the products content and context and can be
used to conduct analysis or further processing.
Monitoring for Precision Agriculture MPA Precision agriculture is a farming management concept based on observing, measuring and responding to inter and intra-field variability in crops.
Mosaic - A raster view of part the earth made from multiple scenes (pictures).
Nadir - The point on a celestial sphere directly below an observer. For satellite imagery, an image taken of a target directly below the satellite is on-nadir, while anything not directly below the satellite is “off-nadir”.
National Aeronautics and Space Administration NASA NASA is a U.S. government agency that is responsible for science and technology related to air and space. The Space Age started in 1957 with the launch of the Soviet satellite Sputnik.
National Geospatial-Intelligence Agency NGA A combat support agency within the United States Department of Defense whose primary mission is collecting, analyzing, and distributing geospatial intelligence in support of national security.
National Reconnaissance Office NRO The U.S. Government agency in charge of designing, building, launching, and maintaining America's intelligence satellites.
Near infrared NIR A method that makes use of the near-infrared region of the electromagnetic spectrum (from about 700 to 2500 nanometers).
Non-sustainable Selective Logging - The exploitative extraction of single trees from only one or a few (high value) species and only one age class (e.g. the biggest trees); may lead to degradation of biodiversity and endangerment of targeted species.
Normalized Difference Vegetation Index NDVI (NIR - red) / (NIR + red) This is a widely used index that has high values for healthy vegetation.
Off- Nadir - Imagery taken at an angle. If the angle is greater than 15 degrees then it is typically considered oblique.
Open Geospatial Consortium, Inc OGC An international specification for making your maps and data available in an open, internationally recognized format over the web.
Open Source Geospatial Foundation OGCeo Home of projects like GDAL, GRASS and PostGIS.
Open Street Map OSM Home of projects like GDAL, GRASS and PostGIS.
Orthorectification Ortho Transforming a picture from space into a "north up" image with geospatial location, including accounting for elevation.
Orthorectified Tile Ortho tile The downloadable GeoTIFFs that are aligned to a cell in a grid.
OSM snapping - Using open streetmap roads (and other linear features) as a target for establishing where our images located on the earth.
PlanetScope - The first three generations of Planet’s optical systems are referred to as PlanetScope 0, PlanetScope 1, and
PlanetScope 2.
Point Collect - Refers to the simplest form of SkySat imagery. The desired target is input as a single lat/lon centerpoint (reference graphic in 'Image' above), with dimensions ~6.8x10sqkm.
PostGIS - A geospatial extension for PostgreSQL.
Projection file PRJ A file with the PRJ extension has become the industry standard for containing information related to a coordinate system.
Quad - A public API term that refers to the data asset for the base resolution of the mosaic. Overview metatiles and additional assets are not visible in the public api.
Radio Frequency RF

The oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around 20 kHz to around 300 GHz.

Radiometric Correction RC The correction of variations in data that are not caused by the object or image being scanned. These include
correction for relative radiometric response between detectors, filling non-responsive detectors and scanner
inconsistencies.
RapidEye RE Part of the SkySat fleet, retired in 2020.
Reflectance Coefficient - The reflectance coefficient provided in the metadata is used as a multiplicative to convert Analytic TOA
Radiance values to TOA Reflectance.
Region of Interest ROI Samples within a data set identified for a particular purpose.
S3 - Simple Storage Service - An Amazon Web Service service providing data storage.
Scene - A single image captured by a satellite. Scenes make up a larger image in the Planet platform. A typical SkySat image will contain approximately 90 overlapping scenes. These are how SkySat images are currently divided for download through the platform. The processing level of a scene determines how much correction, calibration, and post-processing it has undergone: (L0, least amount of processing, raw image → L3B, most processed, processed at all available radiometric levels).
Sensor Correction - The correction of variations in the data that are caused by sensor geometry, attitude and ephemeris.
Sentinel-2 - Copernicus Sentinel-2 is a multispectral imaging satellite constellation operated by the European Space Agency.
Signal to Noise Ratio SNR This compares the level of a desired signal to the level of background noise
SkySat - SkySat refers to the 15-satellite constellation in operation since 2014
Space Situational Awareness SSA Refers to the ability to view, understand and predict the physical location of natural and manmade objects in orbit around the Earth, with the objective of avoiding collisions.
Spacecraft SC A vehicle or machine designed to fly in outer space.
SpatioTemporal Access Catalog STAC Provides a common structure for describing and cataloging spatiotemporal assets.
Standard Operating Procedure SOP A set of step-by-step instructions compiled by an organization to help workers carry out routine operation.
Strip - A series of images taken by a satellite in a single continuous pass.
Strip Collect - Refers to a SkySat image that is longer than the standard 'Point' collect above. Input as 2 separate sets of coordinates - a start and end lat/lon pair, representing the top and bottom of the image. Strips can span as long as 100 km (with the standard 7 km width).
Sun Azimuth - The angle of the sun as seen by an observer located at the target point, as measured in a clockwise direction
from the North.
Sun Elevation - The angle of the sun above the horizon.
Sun Synchronous Orbit SSO A nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time.
Surface Reflectance SR Surface reflectance is the amount of light reflected by the surface of the earth. It is a ratio of surface radiance to
surface irradiance, and as such is unitless, and typically has values between 0 and 1. The Surface Reflectance (SR)
Product is derived from the standard Planet Analytic (Radiance) Product and is processed to top of atmosphere
reflectance and then atmospherically corrected to (bottom of atmosphere or) surface reflectance. Planet uses
the 6S radiative transfer model with ancillary data from MODIS to account for atmospheric effects on the
observed signal at the sensor for the PlanetScope constellation.
Tasking Dashboard TADA Planet’s automated cloud-based platform that allows access to the data you need, when you need it. This is relavent for when tasking a satellite.
Tile Grid System - Ortho tiles are based on a worldwide, fixed UTM grid system. The grid is defined in 24 km by 24 km tile centers,
with 1 km of overlap (each tile has an additional 500 m overlap with adjacent tiles), resulting in 25 km by 25 km
tiles.
Time of Interest TOI Time window within which a customer would like images (usually associated with an AOI as well).
Top of Atmosphere TOA Relevant for seeing the reflectance measured by a space-based sensor flying higher than the earth's atmosphere.
Top of Atmosphere Radiance (or reflectance) TOAR A unit-less measurement which provides the ratio of radiation reflected to the incident solar radiation on a given surface.
Unusable Data Mask or Usable Data Mask UDM The unusable data mask file provides information on areas of unusable data within an image (i.e. cloud and non-imaged areas). The pixel resolution of the file will be roughly 48m. The UDM file has 11m or more of horizontal geo-locational uncertainty and combined with its lower resolution cannot absolutely accurately capture the edges of areas of unusable data. It is suggested that when using the file to check for usable data, a buffer of at least 1 pixel should be considered.
Vignetting - An effect where camera images have less signal further from the center resulting in dim image corners - corrected with flat fields.
Web Feature Service WFS Allows a client to perform data manipulation operations on one or more geographic features.
Web Mapping Service WMS Standard protocol developed by the Open Geospatial Consortium in 1999 for serving georeferenced map images over the Internet. These images are typically produced by a map server from data provided by a GIS database.
Web Processing Service WPS Provides access to calculations or models which operate on spatially referenced data.

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Userlevel 6
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Nice glossary, thanks for compiling and sharing!

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