Geometry Overview

AI-generated Key Takeaways

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• Earth Engine uses the Geometry type to handle vector data, supporting various geometry types based on the GeoJSON specification including Point, LineString, LinearRing, and Polygon, as well as their multi-part versions.

• Geometry objects can be created interactively using the Code Editor tools or programmatically by providing coordinate lists to the respective constructors.

• A LinearRing is a closed LineString, indicated by having the same start and end coordinates.

• Multi-part geometries can be broken down into their individual components using the geometry.geometries() method.

Earth Engine handles vector data with the Geometry type. The GeoJSON spec describes in detail the type of geometries supported by Earth Engine, including Point (a list of coordinates in some projection), LineString (a list of points), LinearRing (a closed LineString), and Polygon (a list of LinearRings where the first is a shell and subsequent rings are holes). Earth Engine also supports MultiPoint, MultiLineString, and MultiPolygon. The GeoJSON GeometryCollection is also supported, although it has the name MultiGeometry within Earth Engine.

Creating Geometry objects

You can create geometries interactively using the Code Editor geometry tools. See the Earth Engine Code Editor page for more information. To create a Geometry programmatically, provide the constructor with the proper list(s) of coordinates. For example:

var point = ee.Geometry.Point([1.5, 1.5]);

var lineString = ee.Geometry.LineString(
  [[-35, -10], [35, -10], [35, 10], [-35, 10]]);

var linearRing = ee.Geometry.LinearRing(
  [[-35, -10], [35, -10], [35, 10], [-35, 10], [-35, -10]]);

var rectangle = ee.Geometry.Rectangle([-40, -20, 40, 20]);

var polygon = ee.Geometry.Polygon([
  [[-5, 40], [65, 40], [65, 60], [-5, 60], [-5, 60]]
]);

In the previous examples, note that the distinction between a LineString and a LinearRing is that the LinearRing is “closed” by having the same coordinate at both the start and end of the list.

An individual Geometry may consist of multiple geometries. To break a multi-part Geometry into its constituent geometries, use geometry.geometries(). For example:

// Create a multi-part feature.
var multiPoint = ee.Geometry.MultiPoint([[-121.68, 39.91], [-97.38, 40.34]]);

// Get the individual geometries as a list.
var geometries = multiPoint.geometries();

// Get each individual geometry from the list and print it.
var pt1 = geometries.get(0);
var pt2 = geometries.get(1);
print('Point 1', pt1);
print('Point 2', pt2);