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Metadata catalogue.

Vector Data

Popular formats: Shapefile; OpenStreetMap file formats; GeoJSON; GML, KML;

Vector topology: Common boundary between two adjacent areas are stored as a single boundary, so that gaps and slivers are impossible. Simple Features and ESRI Shapefiles are non-topological vector formats.

Geometry types: points, lines, polygons. (Faster computations, but extra work for maintenance)

Topological vector geometry types:

  • Basic types:
    • 0D: point, centroid, kernel (3D centroid);
    • 1D: line, boundary;
    • 2D: face (3D area);
  • Derived types:
    • 0D: node (end of lines/boundaries); vertex (non-node points);
    • 2D: area = closed ring of boundaries + centroid; isle = closed ring of boundaries without centroid;
    • 3D: volume = faces + kernel;

GeoJSON

GeoJSON is a JSON extension implementing Simple Features. Native to JavaScript, GeoJSON is a popular format for serving geospatial data on the web, such as drawing leaflet maps or sending vector tiles. Unlike CSV, GeoJSON does not have simple separators between data entries or well-defined types and orders, thus not perfect for streaming.

A GeoJSON feature is an object of "type": "Feature" with geometry and additional properties. A FeatureCollection object is a set of features.

GeoJSON supports the following geometry type specified with coordinates:

  • Point: a single position, specified as an ordered array [longitude, latitude, height];
  • LineString: an array of positions;
  • Polygon: a collection of LinearRing (loops of positions) specifying exterior (counterclockwise) and interior (clockwise) boundaries;
  • Multi-part collections of these types: MultiPoint, MultiLineString, and MultiPolygon.
  • (rare) GeometryCollection is a container for different kinds of geometries.

An awesome list of GeoJSON utilities compiled by Tom MacWright.

Well Known Text

WKT (Well Known Text) Representation (of Simple Features 1.2 geometries):

  1. Point: POINT(- 117.25 35.0)
  2. Line String: LINESTRING(0 10, 20 15, 30 15)
  3. Polygon: POLYGON((0 0,10 10,10 0,0 0),(3 1,4 1,4 2,3 1))
  4. Polyhedral Surface: POLYHEDRALSURFACE(((0 10,0 0,10 0,10 10,0 10)),((0 10,5 15, 10 10,0 10)))
    1. TIN (Triangulated Irregular Netowrk)
  5. Geometry Collection:
    1. Multi Point: MULTIPOINT((0 0),(10 10),(10 0))
    2. Multi Line String: MULTILINESTRING((0 0,10 10,10 0),(3 1,4 1,4 2,5 1))
    3. Multi Polygon: MULTIPOLYGON(((0 0,10 10,10 0,0 0),(3 1,4 1,4 2, 3 1)),((20 20, 30 30, 30 20, 20 20)))

GPS Exchange Format

GPX (GPS Exchange Format) is an XML schema describing:

  • waypoints (wptType): recorded locations;
  • tracks (trkType): one ordered list of waypoints for each continuous span of GPS connection;
  • routes (rteType): an ordered list of routepoints, which represent significant turns or stage points for trip planning.

Latitude and longitude are expressed in decimal degrees using the WGS 84 datum. Elevation is recorded in meters. Dates and times are in Coordinated Universal Time (UTC) using ISO 8601 format.

Rater Data

  1. compressed .jpg, .gif
  2. non-compressed .png, .tiff

Tagged Image File Format (TIFF) Developed by Aldus, now Adobe Systems.

GeoTIFF is a public domain metadata standard which allows georeferencing information to be embedded within a TIFF file.

HDF, NetCDF

Point Cloud Data

Spatial Indexing

Algorithms: quadtree, R-tree

🏷 Category=Geographic Information System