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动态情况下,PPP状态转移矩阵Fk_1是建立成单位矩阵,请问这是按照什么模型的啊? #26

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Hemaihang opened this issue May 8, 2020 · 1 comment

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@Hemaihang
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@XiaoGongWei
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Fk_1是Kalman滤波的参数的转移矩阵(预测矩阵)。Fk_1构建根据天线运动模型确定。

PPP状态预报方程 Xk=Fk_1*Xk_1+Qw
PPP中天线运动状态的预报可由两个参数确定Fk_1和Qw(转移噪声)。

例如XYZ坐标在静态情况下对应的Fk_1为[1 1 1],转移噪声为0;
在动态情况下理论上:

  • 应将dXYZ对应的Fk_1为[0 0 0],转移噪声为inf(无穷大),Xk = 0*dXYZ+inf;
  • 也可以将dXYZ对应的Fk_1为[1 1 1],转移噪声为inf(无穷大),Xk = 1*dXYZ+inf; 并无很大影响
  • 在MG-APP中dXYZ对应Fk_1为[1 1 1],转移噪声为1e3(相当于无穷大),Xk = 1*dXYZ+1e3;
    因为使用的近似坐标列方程,所以dXYZ一般不会超过50m。MG-APP是为了代码计算方便(Fk_1静动态都是单位阵)才这样考虑的。
  • 你也可以将1e3改成更大的数值1e10或者1e12。这样会引起kalman协方差数值预报(Pkk_1 = FtPk_1F.transpose() + Qwk)的不稳定性,Pkk_1 数值差异增大条件数增大,病态性严重。因此先验参数对kalman数值稳定性有影响。一些改进的Kalman和SRIF滤波不会受到这些的影响,这也是MG-APP引入了SRIF滤波的原因

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