Short, practical definitions of the GIS terms this site's converters and guides rely on, from CRS and datum to WKT and the shapefile sidecar files, each linked to the tool or guide where the concept matters most.
Attribute table · Bounding box · .cpg file · Coordinate reference system · Datum · .dbf file · Decimal degrees · Degrees minutes seconds · Degrees decimal minutes · DXF · EPSG code · Feature · FeatureCollection · GDAL / OGR · Geocoding · GeoJSON · Geometry type · GeoPackage · GPX · Latitude & longitude · Layer · Multi-part geometry · Placemark · .prj file · Projection · Raster vs vector · Reprojection · Shapefile · .shx file · SRID · Track · UTF-8 encoding · UTM · Vertex · Waypoint · WebAssembly · WGS84 · WKT
The spreadsheet-like table of non-spatial data attached to a vector layer: one row per feature, one column per field. In a shapefile it lives in the .dbf sidecar; exporting it is the whole point of shapefile to CSV.
The smallest rectangle that contains every feature in a layer, given as minimum and maximum X and Y. GIS software uses it to zoom to a layer, and a wildly wrong extent usually means a coordinate-system mismatch.
A tiny shapefile sidecar that records which character encoding the attribute table uses (for example UTF-8). Without it, accented names and non-Latin text can turn to garbage when the .dbf is opened elsewhere.
The complete recipe that ties coordinates to real places: a datum plus, for projected systems, a map projection. When data lands in the wrong place, the CRS is almost always the culprit; see the guide to coordinate systems and EPSG codes.
The reference model of the Earth's shape that a CRS is anchored to, WGS84 and NAD83 are the ones you will meet most. Two datasets on different datums can disagree by anything from centimetres to a few hundred metres.
The dBASE-format table holding a shapefile's attributes. It caps field names at 10 characters and text fields at 254, which is why long column names get truncated when you convert GeoJSON to shapefile.
Latitude/longitude written as a single decimal number, such as 33.6844, 73.0479. It is the format GeoJSON, KML and most software expect; the coordinate converter translates between DD and the degree-minute forms.
The traditional coordinate notation, 33°41'04"N 73°02'52"E, still common on paper maps, deeds and survey reports. See latitude and longitude formats for how DD, DMS and DDM relate.
A halfway notation, 33°41.07'N, used by marine and aviation GPS receivers. Easy to confuse with DMS at a glance; the digits after the degree symbol mean different things in each.
Autodesk's Drawing Exchange Format, the interchange format of the CAD world. It stores geometry in drawing units with no attribute table and usually no CRS, which drives most of the checks on DXF to shapefile. Background: what is a DXF file?
A short number that unambiguously names a CRS, 4326 is WGS84 latitude/longitude, 3857 is web-map Mercator, 32643 is UTM zone 43N. Far safer to quote than a CRS name, and searchable at epsg.io.
One thing on the map: a single point, line or polygon together with its attributes. A layer is a collection of features of the same geometry type.
The top-level object of a GeoJSON file, an array of features wrapped with a type declaration. It is what you get from any conversion to GeoJSON on this site, such as KML to GeoJSON.
The open-source translator library that virtually every GIS package uses under the hood for format reading and writing. GISConverter runs a full GDAL build compiled to WebAssembly inside your browser; see how the site works.
Turning an address or place name into coordinates (and reverse geocoding is the opposite). Distinct from format conversion: this site converts files that already contain coordinates, it does not look addresses up.
A JSON-based vector format, defined by RFC 7946, that web-mapping libraries read natively. Human-readable, one file, always WGS84; the full story is in GeoJSON format explained.
Whether features are points, lines or polygons (or their multi-part variants). Formats differ in tolerance: GeoJSON mixes types freely in one file, while a shapefile stores exactly one type per layer, a key check when you convert KML to shapefile.
A modern OGC format that packs any number of layers, of any size, into a single SQLite database file. Increasingly the default advice instead of shapefiles; compared head-to-head in GeoPackage vs shapefile.
The GPS Exchange format, an XML schema for waypoints, routes and tracks that practically every GPS device and fitness app speaks. It stores WGS84 coordinates only and has no polygon type; see the GPX file explained.
The angular coordinates of a point on the Earth: latitude north/south of the equator, longitude east/west of Greenwich. The perennial trap is axis order, GIS tradition says lat/lon, but GeoJSON and most file formats store lon/lat (X first).
A set of features of one geometry type sharing one attribute schema and one CRS, the unit that GIS software adds to a map. Some formats hold one layer (shapefile), others hold many (GeoPackage, KML, DXF).
A single feature made of several shapes, a MultiLineString for a route with gaps, a MultiPolygon for an island group. Converters often promote lines to multi-lines for consistency, which is normal and lossless.
KML's word for a feature: a named point, path or polygon with a description balloon and a style. Spreadsheet rows become placemarks when you convert CSV to KML.
The shapefile sidecar holding the layer's CRS as WKT text. Losing it is the single most common cause of data landing in the wrong place; the rescue procedure is in GIS data in the wrong place.
A mathematical flattening of the curved Earth onto a plane so positions can be stated in metres or feet, UTM zones and national grids are examples. Projected coordinates look like large numbers (500000, 3730000) rather than degrees.
Raster data is a grid of pixels (satellite imagery, elevation models); vector data is geometry (points, lines, polygons). This site's converters are vector-focused, since raster imagery needs different handling.
Recomputing coordinates from one CRS to another, degrees to UTM metres, for instance. It is a mathematical transformation, not a relabelling; assigning the wrong CRS name without transforming is how data ends up in the sea.
Esri's 1990s vector format, still everywhere, that is really a family of files (.shp, .shx, .dbf, .prj, .cpg) which must travel together. Its rules and quirks are covered in what is a shapefile?
The shapefile's spatial index, a lookup table that lets software jump straight to feature number N in the .shp. It is required: many programs refuse to open a shapefile without it.
The spatial reference identifier a database uses to tag geometry with its CRS, in practice usually the same number as the EPSG code (4326 and friends). You will meet it in PostGIS and GeoPackage metadata.
A recorded path in a GPX file: an ordered list of trackpoints with optional timestamps and elevations, i.e. where you actually went. Routes are the planned counterpart; the difference matters when you convert GPX to shapefile.
The character encoding that can represent every script, and the safe choice for attribute text. CSV exports here are UTF-8, and shapefile output includes a .cpg declaring it, so names like "Kärnten" or "كراچی" survive conversion.
The Universal Transverse Mercator system: 60 numbered zones, each a projected CRS in metres. Survey and drone data very often arrives in a UTM zone, which is why spreadsheet converters here ask you to confirm the CRS when coordinates look projected.
A single coordinate pair along a line or polygon boundary; geometry is stored as ordered vertex lists. Simplification removes vertices to shrink files, at the cost of shape fidelity.
A single named point in GPS data, a summit, a sample site, a cache. Waypoint lists move between spreadsheets and devices via CSV to GPX and back.
A browser technology that runs compiled native code at near-native speed. It is what makes this site possible: the same GDAL engine a desktop GIS uses, executing inside your tab so files never need uploading.
The World Geodetic System 1984, the datum and lat/lon CRS used by GPS and assumed by KML, GPX and GeoJSON (EPSG:4326). When in doubt about a web or GPS dataset's CRS, WGS84 is the usual answer.
A text notation for geometry, POINT(73.05 33.68), LINESTRING(…), that fits in a spreadsheet cell. This site both reads WKT columns from CSV/Excel input and writes them (as the last column) when exporting shapes to tables. The same notation, confusingly, is also used to describe a CRS inside a .prj file.
