Almost every map example in D3.js will use either GeoJSON or TopoJSON. GeoJSON is an open, standard, JSON-based format for representing basic geographical features as well as the non-spatial properties for those features (such as the name of a city or a landmark).
The core geometries in GeoJSON are points, line strings, and polygons. The basic description of a GeoJSON entity uses the following syntax:
{
"type": name of the type of geometry (point, line string, ...)
"coordinates": one or more tuple of latitude / longitude
}Let's take a look at the four basic types of geometry types available in GeoJSON. A point represents a position in two-dimensional space, and consists of a pair of one latitude and longitude. A point is normally used to specify the location of a feature on a map (such as a building):
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Example |
Representative GeoJSON |
|---|---|
 |
{
"type": "Point",
"coordinates": [30, 10]
}
|
LineString describes a sequence of points which have a line...