GIS Database Management, Geographic Referencing Systems, and Map Projections

Comprehensive vocabulary flashcards covering GIS database concepts, table operations, data sources, GNSS positioning, 3D geographic referencing systems, and 2D map projections.

Database

A structured collection of data files created or manipulated with the assistance of a Database Management System (DBMS).

Database Management System (DBMS)

A software package that allows for the creation, storage, maintenance, manipulation, and retrieval of large datasets distributed over one or more files.

Feature ID (FID)

A unique system-assigned numeric identifier automatically generated by ArcGIS for vector feature layers stored as shapefiles.

Object ID (OID)

A unique identifier generated by ArcGIS for an object, feature, or number attribute record in a non-spatial table.

OBJECTID

A unique identifier automatically generated in ArcGIS specifically for features and records in a geodatabase file.

FIPS Code

Federal Information Processing Standards code maintained by the National Institute of Standards and Technology (NIST), establishing unique numeric identifiers for official administrative boundaries such as census tracts and counties.

Flat File Structure

A database organizational structure where all attribute data and records are stored in a single, large spreadsheet-style table.

Hierarchical Database Structure

A database design structured around one-to-many or parent-to-child branching relationships based on key attributes.

Network Database Structure

A database design that allows complex multi-directional relationships and builds connections across multiple tables beyond strict parent-child hierarchies.

Relational Database Structure

The most widely used database model in GIS, where separate tables (called relations) are linked together by matching records with identical key field values.

Table Join

The operation of virtually appending the fields of a source table to a destination layer table based on a shared common field, recommended for one-to-one and many-to-one relationships.

Table Relate

A functional connection established between two tables in ArcGIS that does not merge them into a single table, recommended for one-to-many and many-to-many relationships.

Spatial Query

A GIS operation (such as 'Select Layer By Location') that selects geographic features in one layer based on their spatial proximity or topological relationship to features in another layer.

Spatial Join

An operation that appends attribute data from one spatial layer to another based on geographic location and spatial relationships rather than a common attribute key.

National Hydrography Dataset (NHD)

A USGS digital spatial dataset representing surface waters (rivers, streams, canals, lakes) organized hierarchically into nested hydrologic units identified by HUC codes.

National Land Cover Database (NLCD)

A land cover classification database provided by the Multi-Resolution Land Characteristics (MRLC) Consortium based on Landsat $30\,\text{m}$ resolution imagery.

Soil Survey Geographic Database (SSURGO)

A detailed soil dataset produced by the NRCS showing mapping units of uniform soil properties for landowners, farmers, and local planners at the farm-to-county level.

State Soil Geographic Database (STATSGO)

A generalized, smaller-scale soil dataset compiled by the NRCS over broader areas than SSURGO, with map units that do not follow SSURGO boundaries.

Census TIGER System

Topologically Integrated Geographic Encoding and Referencing system developed by the U.S. Census Bureau that links geographic boundary files to demographic and statistical census data.

Geospatial Metadata

Comprehensive documentation accompanying GIS data that details identification, lineage, positional accuracy, completeness, spatial reference, and attribute definitions under FGDC standards.

Photogrammetry

The process and science of obtaining reliable geometric measurements and maps of physical landscape features from overlapping aerial imagery or photographs.

GNSS (Global Navigation Satellite System)

An overarching term for satellite constellations providing timing, position, and velocity; requires a minimum of three satellites for a 2D fix and four for a 3D position including altitude.

Ephemeris Error

A positioning error resulting from the difference between the actual orbital path of a GNSS satellite and its predicted position broadcast in the navigation message.

Multipath Error

A GNSS signal error caused when radio waves reflect off structures, terrain, or the ground before reaching the antenna, delaying reception and distorting distance calculations.

Geometric Dilution of Precision (GDOP)

A unitless metric quantifying the geometric arrangement of visible satellites, where widely spaced constellations produce lower values and higher measurement confidence.

Differential Positioning (DGPS)

A technique using simultaneous satellite observations at a known, fixed base station and an unknown roving receiver to calculate and subtract range errors.

Wide Area Augmentation System (WAAS)

A satellite-based augmentation system (SBAS) developed by the FAA using ground reference stations to broadcast real-time differential GPS corrections via geostationary satellites across North America.

WISCORS Network

A network of over $100$ permanent GNSS reference stations operated by WisDOT that broadcasts real-time differential corrections achieving up to $2\,\text{cm}$ accuracy across Wisconsin.

Geographic Coordinate System (GCS)

A three-dimensional spherical reference system that locates points on the Earth's surface using an angular unit of measure, a prime meridian, and a datum based on an ellipsoid.

Parallels

East-west reference lines of latitude that measure angular distance north or south from the equator ($0^\circ$) to the poles ($90^\circ\,\text{N}$ and $90^\circ\,\text{S}$).

Meridians

North-south reference lines of longitude converging at the poles that measure angular distance east or west from the prime meridian in Greenwich ($0^\circ$) to $180^\circ$.

Geoid

The physical equipotential surface of the Earth's gravity field that best approximates global mean sea level, serving as the primary reference surface for measuring elevations.

Oblate Ellipsoid

A mathematically smoothed 3D surface generated by rotating an ellipse about its shorter minor axis to model the Earth's polar flattening for horizontal coordinates.

Ellipsoidal Flattening ($f$)

The degree of compression of an oblate spheroid, defined by the formula $f = \frac{a - b}{a}$, where $a$ is the semi-major axis and $b$ is the semi-minor axis.

Geodetic Datum

A reference framework that defines the orientation, origin, and position of a reference ellipsoid relative to the center or surface of the Earth.

Local Datum

A datum whose reference ellipsoid is fitted to match the Earth's curvature in a specific local region, anchored to a permanently fixed surface origin point.

Global Datum

A geocentric datum whose origin is placed at the Earth's estimated center of mass, providing an optimized ellipsoid fit for the entire planet.

NAD 1927

A regional North American horizontal datum based on the Clarke 1866 spheroid ($a = 6,378,206.4\,\text{m}$) with an origin located at Meades Ranch in Kansas.

NAD 1983

An Earth-centered horizontal datum covering North America derived from ground and satellite measurements, using the GRS 80 ellipsoid with its origin at the Earth's center of mass.

World Geodetic System of 1984 (WGS 84)

A global geocentric reference frame and datum defined by the U.S. Department of Defense using an ellipsoid with $a = 6,378,137\,\text{m}$ and $1/f = 298.257$, used natively by GPS.

International Terrestrial Reference Frame (ITRF)

A series of global realization datums tracking plate motions and crustal deformation in 3D using velocity vectors calculated from continuous international geodetic stations.

NATRF2022

A modern terrestrial reference frame designed to replace NAD83 that aligns initially with ITRF/WGS84 by correcting historical Earth center-of-mass offsets.

Map Projection

The mathematical transformation used to systematically project geographic coordinates from a 3D curved reference ellipsoid onto a flat 2D map surface.

Developable Surface

A geometric surface (specifically a cylinder, cone, or plane) that can be unrolled or flattened into a two-dimensional sheet without tearing or stretching.

Standard Line

A line of tangency or secancy where the developable surface makes contact with the reference globe, exhibiting a scale factor of $1.0$ and zero distortion.

Standard Parallel

A line of tangency or secancy in a map projection that follows a specific line of latitude.

Standard Meridian

A line of tangency or secancy in a map projection that coincides with a line of longitude.

Secant Projection

A projection where the developable surface intersects and cuts through the reference globe, producing two standard lines of exact scale rather than one.

Conformal Projection

A map projection property that preserves true local angles, directions, and shapes around points, while systematically distorting feature areas at smaller scales.

Equivalent (Equal Area) Projection

A map projection property that maintains true relative surface areas across the entire map, inevitably distorting distances, directions, and local shapes.

Azimuthal Projection

A map projection that preserves true compass directions (azimuths) from a central point of projection to all other points on the map.

Equidistant Projection

A map projection that maintains true distance and uniform scale along specified standard lines or radiating outward from a central point.

Universal Transverse Mercator (UTM)

A global projected coordinate system dividing the Earth between $84^\circ\,\text{N}$ and $80^\circ\,\text{S}$ into $60$ north-south zones, each $6^\circ$ of longitude wide and numbered eastward from the $180^\text{th}$ meridian.

False Easting and False Northing

Arbitrary linear constants added to the origin of a projected coordinate system to keep all coordinates positive and eliminate negative coordinate values within a mapped zone.

Scale Factor (SF)

The unitless ratio of local map scale to principal globe scale, defined as $\text{SF} = \frac{\text{Local Scale}}{\text{Principal Scale}}$, equaling $1.0$ along standard lines.

On-the-Fly Projection

A display feature in ArcGIS Pro that temporarily reprojects layers with different coordinate systems to match the map frame's projection dynamically without altering the source data files.