code: function Velocity(properties) {
          if (properties)
              for (var keys = Object.keys(properties), i = 0; i < keys.length; ++i)
                  if (properties[keys[i]] != null)
                      this[keys[i]] = properties[keys[i]];
      }
docs: Properties of a Velocity.
  @exports IVelocity
  @interface IVelocity
  @property {number} [x] x速度
  desc: 载具在x方向上的速度，使用N-E-D (North-East-Down)，以米为单位
  unit: m
  @property {number} [y] y速度
  desc: 载具在y方向上的速度，使用N-E-D (North-East-Down)，以米为单位
  unit: m
  @property {number} [z] z速度
  desc: 载具在z方向上的速度，使用N-E-D (North-East-Down)，以米为单位
  unit: m
  @property {number} [gspeed] 地速
  desc: 载具的地速，米/秒 精确到小数点后1位
  unit: m
   
  Constructs a new Velocity.
  @exports Velocity
  @classdesc Represents a Velocity.
  @constructor
  @param {IVelocity=} [properties] Properties to set