Glossary

API: Acronym for Application Programming Interface. A set of interfaces, protocols, and tools that application developers use to build or customize a software program.

Aspect: A visualization of the compass direction that a topographic surface faces.

ASPRS Specifications: A set of .las specifications developed by the American Society for Photogrammetry and Remote Sensing. For example, ASPRS specifies that building LiDAR data is stored in class code 6. More details can be found here.

Attribute: Nonspatial information about a geographic feature, usually stored in table and linked to the feature by a unique identifier.

Contour Lines: Lines on a map that connect points of equal elevation measure. A wider gap between lines indicates a more gradual change in elevation. Contour lines can either be open or closed, the latter indication of a hill or depression. Which of the two cannot be determined unless the lines are labeled and/or overlay an elevation map.

Dataset: A collection of data relating to a particular subject, that can be manipulated and/or processed by a computer. Examples of datasets used in geospatial context are multiple files organized in a set based on different types of data in the same location, and the same type of data spread across different locations.

DEM: Acronym for Digital Elevation Model. A type of elevation model that represents the earth’s surface without adding additional features above the ground (sometimes referred to as bare earth).

DSM: Acronym for Digital Surface Model. A type of elevation model that represents the earth’s surface with objects above the ground included (e.g. trees, buildings).

Elevation Model: A generic term for a 3D representation of a terrain’s surface, created using elevation data. DEMs and DSMs are both types of elevation models.

EPSG: A type of SRID defined by the European Petroleum Survey Group (EPSG). Each code is a number that represents a unique coordinate system, datum, spheroid, unit, and/or other geodetic parameter. An example of an EPSG code is 26910; this EPSG code specifies the NAD83 datum and UTM projection of UTM10N.

Feature: A representation of a real world object on a map. In GIS, features are most commonly represented as a point, polyline or polygon.

GeoJSON: GeoJSON is a file format that stores geographic vector data and associated attributes. It is based on JavaScript Object Notation (JSON). The extension is .json or .geojson. More details can be found here.

Hillshade: A three-dimensional effect that provides a sense of visual relief for cartography based on a hypothetical illumination of a surface, according to a specified azimuth and sun altitude.

KML: Acronym for Keyhole Markup Language. A file format that stores geographical data such as vectors, rasters, imagery, and/or associated content such as attributes and HTML. It is based on Extensible Markup Language (XML), and the extensions are .kml or .kmz for compressed KML files. It is developed and maintained by Google and used extensively by Google Earth. More information can be found here.

Layer: The visual representation of a geographic dataset in any digital map environment. Layers can usually be toggled on and off to produce the ideal visual output.

LiDAR: Acronym for Light Detection and Ranging. An active remote sensing technique that uses lasers to measure distances to objects.

LiDAR Classification: A process in which LiDAR data points are assigned into a class that describes the type of object they are, such as ground, vegetation, building, etc.

LiDAR Coregistration: Accurately registering two LiDAR datasets onto a common coordinate system so that datasets that overlap are tied together closely.

LiDAR Registration: The act of accurately positioning LiDAR points onto a coordinate system, which includes ensuring all processing components in the workflow of a LiDAR point cloud output are aligned with respect to the common coordinate system.

LiDAR Returns: Each laser pulse emitted from a LiDAR sensor captures several returns, and these returns are contained in point cloud data as discrete 3D points. Each point captures a return from a laser pulse, and there can be up to 15 returns per laser pulse. For example, a LiDAR return can be indicated as the first return out of four, if only four were captured on a target.

Metadata: Information that describes the content, quality, condition, origin, and other characteristics of spatial data or other information.

Point cloud: A set of data points in three-dimensional (3D) space commonly used to represent LiDAR data. There are many additional types of 3D scanners that can produce a point cloud output.

Segmentation: The process of extracting features from data and/or imagery, based on objects or types of features (e.g. roads, water bodies). The pixels or point data features are grouped into a segment.

Service: Shorthand term for a web service or a capability that is requested as-a-service from an API endpoint. This should not be confused with the terms ‘professional service’ or ‘consulting service’ relating to work performed under a contracted statement of work.

Shapefile: A file format that stores geographic vector data and associated attributes. The shapefile was initially developed by Esri, but has become a defacto standard for many software platforms. The primary file has a .shp extension, though additional sidecar files are needed to correctly use a shapefile. For more details, click here.

Slope: A visualization of the steepness of a surface measured either in percentage or degrees.

Spatial Object: A geographic structure or phenomenon represented spatially. Usually references digital objects which can be used in analysis, comparisons, and data management.

SRID: Acronym for Spatial Reference Identifier. The SRID is a part of the spatial reference system’s database management. SRIDs are used to reference records in the database detailing the coordinate system metadata within the geospatial data. For example, SRID 4326 refers to the authority defined by European Petroleum Survey Group (EPSG) and has its own unique coordinate system attributes.

Topo (Topographic) Change: An analysis that detects topographic surface changes between two datasets, highlighting the quantity of land added or removed. It is usually provided in the form of raster data.

WMS: Acronym for Web Map Service. A protocol developed by the Open Geospatial Consortium for serving map images as a service. These images are georeferenced, usually served in a bitmap format (e.g. .png, .gif, .jpeg), and can include vectors.

WMTS: Acronym for Web Map Tile Service. A protocol developed by the Open Geospatial Consortium for serving map tiles as a service. These tiles are georeferenced and rendered either in advance or in real-time.

Zoom Levels: Also known as Z Levels. A commonly used reference for describing the area of the world visible on a map. Zoom Level 0 (Z0) represents global scale (roughly 1:500,000,000), and Z21 represents building scale (roughly 1:500). In terms of map tile generation, Z Level is based on a quadtree data structure where each level contains four times as many tiles as the previous.