Cartography Terminology

Acronyms, abbreviations, and technical jargon used in GIS, digital cartography, and remote sensing.

AGF (GPS Phase Ambiguity)

The unknown integer representing the number of complete wavelengths between satellite and receiver in GPS carrier-phase measurement. Integer ambiguity resolution is key to achieving centimeter-level accuracy in differential GNSS positioning.

AOI (Area of Interest)

A geographic area selected for spatial query or analysis. In GIS it is typically represented as a clipping polygon or bounding box used in spatial filters for APIs such as the OSM Overpass API.

API GDAL

The Application Programming Interface of the GDAL (Geospatial Data Abstraction Library). Provides uniform read/write access to over 200 raster and vector formats. Available in C/C++, Python (osgeo.gdal), and Java.

BBOX (Bounding Box)

A delimiting rectangle circumscribing a geometry or geographic dataset, defined by minimum and maximum coordinates (minX, minY, maxX, maxY). Used as a first-pass spatial filter in GIS queries and cartographic APIs.

Cadastral Parcel

A cadastral unit: a polygon that uniquely identifies a land parcel in the cadastre. In Italy managed by the Agenzia delle Entrate via the SISTER system; geometries are referenced in Gauss-Boaga East/West (EPSG:3003 or 3004).

CDM (Cartographic Data Model)

A conceptual schema describing how geographic data is organized, including object types, topological relationships, and attributes. Used in the design phase of spatial databases.

CRS (Coordinate Reference System)

A reference system for geographic coordinates. Includes datum, ellipsoid, projection, and unit of measure. Identified in the EPSG registry with numeric codes. Every GIS layer has a CRS; mismatched CRS between layers is the most common cause of cartographic misalignment.

CSW (Catalogue Service for the Web)

An OGC standard for publishing and searching metadata of geographic resources. Used in geoportals for INSPIRE-compliant metadata harvesting.

DGN (Design)

Bentley MicroStation vector format. Present in some technical cartography datasets. GDAL supports reading DGN v7 and v8.

DXF (Drawing Exchange Format)

Autodesk CAD vector format. Often used for topographic survey data in CAD format before conversion to GIS. GDAL supports reading and writing DXF.

ECEF (Earth-Centered, Earth-Fixed)

Geocentric Cartesian coordinate system with origin at the Earth's center, Z-axis toward the North Pole, X-axis toward the Greenwich meridian. Used internally by GPS and in 3D datum transformations.

The European SBAS (Satellite-Based Augmentation System) that improves GPS accuracy in Europe (typically from 3–5 m to 1–3 m) via differential correction signals transmitted from geostationary satellites. Free for civil use.

ENC (Electronic Navigational Chart)

A digital nautical chart conforming to the IHO S-57 standard. Used in ECDIS (Electronic Chart Display and Information System) for maritime navigation.

EPSG:3857

Web Mercator Auxiliary Sphere: the spherical Mercator projection used by Google Maps, OpenStreetMap tiles, Bing Maps, ESRI. Not suitable for European official cartography (INSPIRE mandates ETRS89/UTM). Appropriate for web tile visualization, not geodetic measurements.

EPSG:4326

WGS84 Geographic CRS: the latitude-longitude geographic coordinate system in WGS84. Used by GPS, GeoJSON, KML, global datasets. OGC coordinate order: latitude (Y), longitude (X); inverted (longitude, latitude) per RFC 7946 GeoJSON.

EPSG:32632

UTM Zone 32N on WGS84: metric plane coordinate system for the western part of Italy (approximately west of the 12°E meridian). Units: meters. Origin: intersection of central meridian (9°E) with equator, false Easting 500,000 m.

EPSG:32633

UTM Zone 33N on WGS84: metric plane coordinate system for the eastern part of Italy (approximately east of 12°E). Central meridian 15°E.

ETRS89 (European Terrestrial Reference System 1989)

European geodetic datum anchored to the Eurasian tectonic plate. Practically coincident with WGS84 at topographic precision (difference < 1 m in 2024). Mandatory datum for INSPIRE-compliant cartography in Europe.

FME (Feature Manipulation Engine)

Commercial software (Safe Software) for spatial data transformation and conversion. Industry standard for geographic ETL pipelines.

GDAL (Geospatial Data Abstraction Library)

Open source library (MIT/X license) for reading and writing raster and vector geospatial data. Includes OGR for vector data. Foundation of the open source GIS ecosystem: used by QGIS, PostGIS, MapServer, GeoServer.

Geoid

An equipotential surface of the Earth's gravitational field coinciding with mean sea level. Used as the reference for orthometric height. Geoid undulation (N) is the difference between ellipsoidal and orthometric heights; in Italy it typically ranges from +30 m to +50 m.

GeoPackage

An open vector and raster format based on SQLite. OGC standard alternative to Shapefile, without its limitations (supports UTF-8, long field names, mixed geometries, raster). Supported by QGIS, GDAL, PostGIS.

GeoServer

An open source web server implementing OGC standards (WMS, WMTS, WFS, WCS, WPS). Distributes geographic layers from heterogeneous data sources (PostGIS, Shapefile, GeoTIFF) in standard formats.

GML (Geography Markup Language)

An OGC XML-based standard for encoding geographic information. Basis of INSPIRE formats and WFS 2.0 services.

GPKG

GeoPackage file extension (.gpkg). Recommended as the exchange format replacing Shapefile in INSPIRE and EuroGeographics specifications.

GPS (Global Positioning System)

US satellite positioning system with over 30 satellites in MEO orbit. Output coordinates: WGS84. Civil accuracy: 3–5 m with a single-frequency receiver; sub-metric with SBAS or RTK differential positioning.

HDOP (Horizontal Dilution of Precision)

A dimensionless index measuring degradation of horizontal accuracy due to satellite constellation geometry. Values: < 1 excellent, 1–2 very good, 2–5 good, > 5 poor. Provided by GNSS receivers in NMEA GGA/GSA messages.

HGT

Binary elevation format used by SRTM data (NASA). Each file covers a 1° × 1° square of latitude/longitude. The filename encodes the SW corner position (e.g., N44E011.hgt for the square with SW corner at 44°N, 11°E). Datum: WGS84.

IHO (International Hydrographic Organization)

International organization that establishes standards for nautical charts and hydrographic data. Publishes specifications S-57 (ENC) and S-100 (framework for new digital hydrographic products).

INSPIRE

Infrastructure for Spatial Information in Europe: EU Directive 2007/2/EC requiring EU countries to make public geographic datasets interoperable across 34 themes. Mandates ETRS89 as datum, GML as exchange format, CSW for metadata discovery.

ISO 19111

ISO/TC211 standard defining the concepts of spatial reference systems (CRS). The conceptual model underlying the EPSG registry.

KML (Keyhole Markup Language)

XML format developed by Google for visualizing geographic data in Google Earth and Google Maps. Supports points, lines, polygons, image overlays, and tours. Coordinates in WGS84 in longitude, latitude, altitude order.

LAS / LAZ

Formats for LiDAR point clouds. LAS is the standard ASPRS binary format; LAZ is the lossless compressed version (about 5-10× smaller than LAS). Managed by libLAS and modern PDAL versions.

LIDAR

Light Detection and Ranging. Active laser remote sensing technology producing high-density 3D point clouds (from 4 to over 100 points/m²). Files in LAS/LAZ format; common processing software includes LAStools, CloudCompare, PDAL.

MGRS (Military Grid Reference System)

A grid-based referencing system based on UTM and UPS. Encodes position as an alphanumeric string (e.g., 32TMQ0012345678). Used by outdoor GPS devices and NATO military standards.

NAD83 (North American Datum 1983)

North American geodetic datum. Not relevant for Italy but frequently encountered in datasets from the USA and Canada. Practically coincident with WGS84 at topographic precision.

NMEA 0183

Serial communication standard for GPS/GNSS receivers. NMEA messages GGA, RMC, GSA, GSV provide position, velocity, signal quality. NMEA parsing is necessary for integrating GPS receivers into embedded and IoT applications.

OGC (Open Geospatial Consortium)

International organization that develops open geographic standards: WMS, WMTS, WFS, GML, WKT, Simple Features, GeoPackage, OGC API Features.

OGR

The vector component of GDAL for reading and writing geographic vector formats. The ogr2ogr command-line tool is the standard for format conversion (e.g., Shapefile → GeoJSON → GeoPackage).

OSM (OpenStreetMap)

Open collaborative geographic database, ODbL license. Contains over 9 billion nodes with geometries and tags. The Overpass API enables spatial and attribute queries. Slippy map tiles: zoom 0-19, coordinates in EPSG:3857 (Web Mercator).

OWS (OGC Web Services)

Collective term for OGC web services (WMS, WFS, WCS, WMTS, WPS). Standard for interoperability between distributed GIS systems.

PDAL (Point Data Abstraction Library)

Open source library for reading, writing, and processing point clouds (LAS, LAZ, BPF, COPC). JSON-configurable PDAL pipelines for filtering, classification, transformation, and DEM generation from LiDAR.

PROJ (Cartographic Projections Library)

Open source C library (MIT license) for geographic coordinate transformations. Handles projections, datum shifts (including NADCON, NTv2 grid shifts for Italy), and CRS conversions. Foundation of pyproj (Python) and R-proj4.

RINEX (Receiver Independent Exchange Format)

ASCII standard format for raw GNSS observation data (pseudorange, carrier phase, Doppler, SNR). Used for differential post-processing and geodetic network computation. Current versions: RINEX 3.04, RINEX 4.

RTK (Real-Time Kinematic)

A differential GNSS positioning technique achieving centimeter-level accuracy in real time via corrections transmitted from a base station to a rover. Used in surveying, precision agriculture, UAV surveys.

SBAS (Satellite-Based Augmentation System)

A GNSS augmentation system that broadcasts differential corrections and integrity messages from geostationary satellites. EGNOS is the European SBAS. Improves GPS accuracy from 3–5 m to 1–3 m.

SHP / DBF / SHX

The three mandatory components of an ESRI Shapefile. .shp contains geometries in WKB, .dbf contains attributes in dBASE IV format, .shx is the spatial index of offsets in the .shp file.

SRTM (Shuttle Radar Topography Mission)

NASA mission (2000) that acquired the first global high-resolution DEM. SRTM3: about 90 m resolution; SRTM1: about 30 m (open since 2014). Datum: WGS84. Format: HGT. Available at earthexplorer.usgs.gov, opentopography.org.

TIN (Triangulated Irregular Network)

A vector terrain model based on irregular triangles built from sampled elevation points. Alternative to the regular raster DEM; suited to surfaces with variable point density (e.g., post-decimation LiDAR output).

TMS (Tile Map Service)

A specification for distributing raster map tiles. Similar to WMTS but less formal. OpenStreetMap and Google Maps tiles use TMS structure with EPSG:3857 coordinates and z/x/y numbering.

UTM (Universal Transverse Mercator)

Global plane coordinate system. Divides the Earth into 60 longitudinal zones of 6°. Coordinates in meters (Easting, Northing). Linear scale distortion less than 0.04% within the zone (±3° of the central meridian). Italy is in zones 32N (EPSG:32632) and 33N (EPSG:32633).

VRT (Virtual Dataset)

A GDAL virtual format that mosaics or transforms existing raster datasets without duplicating data. Useful for building SRTM DEM or orthophoto mosaics distributed across multiple HGT/GeoTIFF files.

WCS (Web Coverage Service)

An OGC service for distributing georeferenced raster data (DEMs, satellite imagery) with access to pixel values and coordinates. Complementary to WMS (which provides only graphical rendering).

WGS84 (World Geodetic System 1984)

Global geodetic datum adopted by GPS. Ellipsoid parameters: a = 6,378,137 m, f = 1/298.257223563. EPSG:4326 for geographic lat/lon coordinates; EPSG:4979 for 3D coordinates (lat, lon, h).

WKB (Well-Known Binary)

The OGC standard binary format for geographic geometries. Used internally by PostGIS, GDAL, GEOS. More efficient than WKT for serialization and storage.

WMTS (Web Map Tile Service)

OGC standard for distributing pre-rendered map tiles at fixed zoom levels. More performant than WMS for web applications. Tile coordinates use the TileMatrixSet grid, based on EPSG:3857 for most public services.

WPS (Web Processing Service)

OGC standard for remote execution of geospatial algorithms (buffer, intersection, raster analysis) via web services. Implemented by GeoServer and Zoo-Project.