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TopoJSON (.topojson)

Background & Context

    • TopoJSON GIS format.
    • Geospatial data interchange format based on JavaScript Object Notation (JSON).
    • An extension of the GeoJSON format.
    • Suitable for encoding geographic data into shared topology.

Import

  • Import["file.topojson"] imports the data associated to the vector geo primitives stored in the given file.
  • Import["file.topojson",elem] imports the specified element from a OSM file.
  • Import["file.topojson",{{elem1},{elem2},…}}] imports multiple elements.
  • The import format can be specified with Import["file","TopoJSON"] or Import["file",{"TopoJSON",elem,…}].
  • See the following reference pages for full general information:
  • Importimport from a file
    CloudImportimport from a cloud object
    ImportStringimport from a string
    ImportByteArrayimport from a byte array

Import Elements

  • General Import elements:
  • "Elements" list of elements and options available in this file
    "Summary"summary of the file
    "Rules"list of rules for all available elements
  • Data representation elements:
  • "Data"graphics primitives for each layer
    "Graphics"all layers combined into a single graphics object
    "GraphicsList"list of graphics representing the layers of an OSM archive
  • Import by default uses the "Graphics" element for the TopoJSON format.
  • Import["file","Data"] returns an expression of the form {layer1,layer2,…} . Individual layers are given as a list of rules representing the geometry, as well as numerical and textual information associated with the features.
  • Metainformation elements:
  • "LayerNames"all layer names, given as a list of strings
    "LayerTypes"what graphics primitives comprise each layer
    "SpatialRange"range of geographic coordinates, typically given in decimal degrees
  • The TopoJSON format does not contain information about the coordinate reference system being used. GeoGraphics will assume that this data corresponds to the "Equirectangular" projection in degrees.
  • Accessing low-level metainformation from the file:
  • "CoordinateSystemInformation"raw parameters of the coordinate system as stored in the file
  • See the reference page for GeoProjectionData for full information on cartographic projections.

Options

Examples

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Basic Examples  (1)

Import a JSON file in the TopoJSON format, rendering its contents as a GeoGraphics object:

Scope  (1)

Import simultaneously the datum and the list of layer names:

Import Elements  (7)

Available Elements  (1)

List of available import elements:

Data Representation  (3)

"Data"  (1)

Import of the full dataset:

"Graphics"  (1)

Import the full set of graphics primitives and represent them using GeoGraphics:

This is equivalent to using an explicit "Graphics" element:

"GraphicsList"  (1)

Import a list of different geo primitives, in this case, polygons:

Metadata  (3)

"LayerNames"  (1)

Import the list of layers:

"LayerTypes"  (1)

Import the geometric type of each layer:

"SpatialRange"  (1)

Import the geodetic bounds in the form {{latmin,latmax},{lonmin,lonmax}}:

Applications  (1)

Extract geometric data from a TopoJSON file:

Separate the different geometric primitives:

Represent these primitives in a map: