GeoJSON Overview

The GMP ground motion format is an extension of the GeoJSON “FeatureCollection” format for points. For example, a simple collection of two points in GeoJSON would look like this:

{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": {
        "name": "Example Point 1"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [-117.3, 35.5, 10.0]
      }
    },
    {
      "type": "Feature",
      "properties": {
        "name": "Example Point 2"
      },
      "geometry": {
        "type": "Point",
        "coordinates": [-120.1, 37.2, 2.0]
      }
    }
  ]
}

There are a few key aspects of the JSON format that users should be familiar with:

• Dictionaries consist of key-value pairs and begin with an open brace { and end with a closed brace }. In the example above, the base structure of the format is a dictionary, with keys of “type” and “features”. Note that the order of the entries in a dictionary does not matter and is ignored.

• A list is an array of values separated by commas and begins with an open bracket [ and ends with a closed bracket ]. The values can be anything, such as a number, string, another list, or a dictionary. The “features” key in the base dictionary is itself a list of dictionaries, each of which corresponds to one point.