ee.Feature.buffer

Returns the input buffered by a given distance. If the distance is positive, the geometry is expanded, and if the distance is negative, the geometry is contracted.
UsageReturns
Feature.buffer(distance, maxError, proj)Feature
ArgumentTypeDetails
this: featureElementThe feature the geometry of which is being buffered.
distanceFloatThe distance of the buffering, which may be negative. If no projection is specified, the unit is meters. Otherwise the unit is in the coordinate system of the projection.
maxErrorErrorMargin, default: nullThe maximum amount of error tolerated when approximating the buffering circle and performing any necessary reprojection. If unspecified, defaults to 1% of the distance.
projProjection, default: nullIf specified, the buffering will be performed in this projection and the distance will be interpreted as units of the coordinate system of this projection. Otherwise the distance is interpereted as meters and the buffering is performed in a spherical coordinate system.

Examples

Code Editor (JavaScript)

// Polygon feature of Serengeti National Park.
var feature = ee.FeatureCollection('WCMC/WDPA/current/polygons')
                  .filter('ORIG_NAME == "Serengeti National Park"')
                  .first();

// Cast the resulting object as an ee.Feature so that the call to the buffer
// method is unambiguous (first() and buffer() are shared by multiple classes).
feature = ee.Feature(feature);

// Generate buffered features out and in from the original boundary.
var bufferOut = feature.buffer(10000);  // 10 km out
var bufferIn = feature.buffer(-10000);  // 10 km in

// Display the features on the map.
Map.addLayer(bufferOut, {color: 'red'}, 'Buffer out');
Map.addLayer(feature, {color: 'blue'}, 'No buffer');
Map.addLayer(bufferIn, {color: 'yellow'}, 'Buffer in');
Map.setCenter(34.8407, -2.398, 8);