GIS in the Life Sciences midterm 1

Vocabulary flashcards covering core GIS principles, geodesy, datums, map projections, vector/raster data structures, geoprocessing operations, remote sensing, and LiDAR concepts.

SAIL

Spatial Analysis Instructional Laboratory at ODU.

Oblate Spheroid

The shape of the Earth, characterized by being slightly flattened at the poles and wider around the equator.

Geodesy

The study of the shape, size, and position of the Earth.

Ellipsoid

A smooth, mathematical model that approximates the shape of the Earth.

Geoid

An irregular model of the Earth based on Earth's gravity, representing idealized mean sea level.

Datum

A reference framework or model used to specify locations on Earth.

Horizontal Datum

A reference framework used for latitude/longitude or X/Y locations.

Vertical Datum

A reference framework used for elevation and height.

NAD83

North American Datum of 1983; a horizontal datum commonly used in North America.

WGS84

World Geodetic System 1984; a global reference system commonly associated with GPS.

Orthometric Height ($H$)

Height measured above the geoid, basically representing elevation above mean sea level.

Ellipsoidal Height ($h$)

Height measured above the reference ellipsoid.

Geoid Height ($N$)

The distance or separation between the geoid and the reference ellipsoid.

Height Formula

$h = H + N$, where $h$ is ellipsoidal height, $H$ is orthometric height, and $N$ is geoid separation.

Map Projection

A mathematical method for transforming the curved Earth onto a flat map.

Equal-Area Projection

A projection type that preserves relative area sizes, such as the Gall-Peters projection.

Conformal Projection

A projection type that preserves local angles and shapes of small features, such as the Mercator projection.

Equidistant Projection

A projection type that preserves distance and scale along specific lines or from specific points.

Azimuthal Projection

A projection type that preserves direction and angles from a specific point.

Compromise Projection

A map projection that does not perfectly preserve one property, but tries to balance multiple types of distortion.

Developable Surfaces

Surfaces imagined placed around Earth before flattening, specifically cylinders, cones, and planes.

Tangency

A map projection case where the developable surface touches the globe.

Secancy

A map projection case where the developable surface cuts through the globe.

Great Circle

A circle around Earth whose center matches Earth's center, representing the shortest route between two points on a sphere.

Topology

The study of how spatial features are connected or arranged in relation to one another (e.g., connectivity, adjacency, containment).

Generalization

Simplifying map features to make them easier to see at a smaller scale by removing unnecessary detail while retaining important information.

Raster Data

Spatial data composed of a grid of cells or pixels where each cell stores a numeric or categorical value.

Minimum Mapping Unit (MMU)

The smallest feature or area that can be reliably represented on a map, commonly encountered in satellite imagery.

Vector Data

Spatial data representing features using points, lines, and polygons; best suited for objects with distinct boundaries.

KML (Keyhole Markup Language)

An XML-based end-user file format originally created for Google Earth that is now standardized; its zipped version is KMZ.

GeoJSON

A specific version of JSON where geometry is specified, storing coordinates and attributes for web maps.

GPX (GPS eXchange Format)

An XML-based end-user format designed for GPS data that stores recorded time information and typically supports WGS84 coordinates.

Esri Shapefile (SHP)

A shareable vector file format that stores a single layer and requires multiple sidecar files to be transferred together.

GeoPackage (GPKG)

An open-source container alternative to Esri File Geodatabase (GDB) capable of storing any number of layers.

Darwin Core

A database standard used for sharing biodiversity information.

Erase

A Boolean NOT operation in GIS that acts as the opposite of a clip.

Union

A Boolean OR overlay operation that keeps all boundaries and attributes from the input layers.

Intersect

A Boolean AND overlay operation that combines features and attributes where layers overlap.

Symmetrical Difference

A Boolean XOR operation that only maintains areas that are not shared between input layers.

Thiessen (Voronoi) Polygons

Polygons defining the area that is closer to one point than to any other point in a dataset.

Buffer

A proximity analysis tool that creates a zone or boundary around a feature at a specified distance.

Convex Hull

A minimum bounding polygon that contains no inward flexing (concave angles) around a set of points.

Raster Pyramids

Reduced-resolution raster layers recalculated at different zoom levels to enable efficient viewing.

Mosaicking

The process of pasting adjacent rasters together to create a single, larger raster grid.

Euclidean Distance

Straight-line distance measured from a source to a raster cell.

Cost Distance

Euclidean distance modified by applying a cost or impedance factor, such as slope weighting.

Focal Statistics

A neighborhood raster operation that calculates a statistic within a moving window and assigns the value to the center cell.

Zonal Statistics

An analysis that calculates summary statistics from a continuous raster within zones defined by another raster or polygon layer.

Remote Sensing

Taking measurements or collecting observations without coming into direct contact with the feature of interest.

Passive Remote Sensing

Remote sensing systems, such as optical or thermal sensors, that receive naturally reflected or emitted energy without sending out their own signal.

Active Remote Sensing

Remote sensing systems, such as RADAR and LiDAR, that emit their own energy pulses and measure the returned signal.

RADAR

RAdio Detection And Ranging; an active microwave sensor that measures backscatter to detect features and create terrain models.

LiDAR

Light Detection And Ranging; an active sensor that emits visible or infrared laser pulses to measure distance and elevation.

Orthorectification

A process that removes vertical relief displacement from aerial photography to give the image a uniform scale.

Digital Terrain Model (DTM)

A raster representation of the bare ground terrain surface calculated by measuring elevation values.

Digital Surface Model (DSM)

An elevation model capturing the bare ground surface plus all features elevated above the ground (such as trees and buildings).

Normalized Digital Surface Model (nDSM)

A model showing the height of above-ground features, calculated as $DSM - DTM = nDSM$.

Triangulated Irregular Network (TIN)

A vector terrain model that connects elevation measurement points into contiguous, non-overlapping triangles composed of nodes, edges, and faces.

Inertial Measurement Unit (IMU)

A LiDAR system component that records the laser's angular orientation relative to the ground, measuring roll, pitch, and yaw.

Point Cloud

A collection of dense 3D measurement points produced by LiDAR that represents surfaces and objects.

EPSG Codes

Standardized numeric codes used to identify coordinate reference systems (CRS).