成员变量 类型: String # static readonly degrees RadiusUnit.degrees，度 Default Value: 'degrees' 类型: String # static readonly kilometers RadiusUnit.kilometers，千米 Default Value: 'kilometers' 类型: String # static readonly meters RadiusUnit.meters，米 Default Value: 'meters' 类型: String # static readonly miles RadiusUnit.miles，英里 Default Value: 'miles' 类型: String # static readonly nauticalMiles RadiusUnit.nauticalMiles 海里 Default Value: 'nautical-miles' 类型: String # static readonly yards RadiusUnit.yards，码 Default Value: 'yards'
