Question

Hi,all. I want to process spaceborne gps data(champ grace etc.) with SolverPPP. As example 8 and example 9 are all process static obs data with a static model, I have to make some changes on SolverPPP. I make a copy of SolverPPP and change class name to SolverLEO.After going through the code, I found lots of work to do,and wish you can give me some help or suggestions. SolverPPP use a static model state vector (ztrop_wet,px py pz,cdt,[N...]), and I want to use a new kinematic state vector (px,py,pz,vx,vy,vz,cdt,[N...]),[px py px] and [vx vy vz] stand for position and velocity.

1 I try to change the default equation of the solver.*defaultEqDef. If I add [vx vy vz] to enum TypeID::ValueType{}. Is the follow changes ok?
enum TypeID::ValueType
{
    ...
    vx
    vy
    vz
    Last
    Placeholder = Last+1000
}

*2 change the kalman matrixs
phiMatrix=
{
    Ip3      Icdt3           o           o
    o         Iv3            o           o
    o          o           Ocdt1         o
    o          o             o          Inm
}
qMatrix
{
    Qp3        o            o            o
    o          Qv3          o            o
    o          o   
}

Dear Mr. Wei:

In order to do kinematic PPP-like processing with SolverPPP you do not have to change SolverPPP. You just have to change the default stochastic model being used, with instructions like:

WhiteNoiseModel newCoordinatesModel(100.0);
pppSolver.setCoordinatesModel(&newCoordinatesModel);

I understand you want to add new velocity state variables to the filter, so you should modify TypeID to include them. Just don't forget to change both TypeID.hpp and TypeID.cpp in a coherent way.

However, I must warn you that your problem will NOT come from the filter: A LEO moves very fast, so you'll have several issues to deal with:

  • If you want to use precise ephemeris, you must implement a way to also use 30 seconds precise clocks.

  • You must carefully tune the cycle slip objects and arc marker to fit your applications.

  • You'll have a lot of short arcs due to the high satellite speed. This will impair proper convergence of ambiguities.

  • Adding new variables to your filter will only worsen the ambiguities problems.

I suggest you to start with a very simple filter, and then add more variables to your state vector in a very careful way.

I also suggest you to check this thesis written by one of my colleagues:

http://www.tdx.cat/TDX-0312109-123420/

Best regards,

Dago

Dear Dago:

Thanks for your suggestions and doctoral thesis,I'll have a try.

Best regards,

Wei

-- DagobertoSalazar - 30 Mar 2009
Topic revision: r5 - 12 Jun 2015, UnknownUser
 

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