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Skip rotation in Bancroft method

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This commit is contained in:
Carles Fernandez 2023-04-01 18:09:35 +02:00
parent 16ae683717
commit 67c6dbcfda
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GPG Key ID: 4C583C52B0C3877D
1 changed files with 12 additions and 30 deletions

42
src/algorithms/libs/rtklib/rtklib_pntpos.cc

@ -610,47 +610,29 @@ double lorentz(const arma::vec &x, const arma::vec &y)
// Bancroft method (see https://gssc.esa.int/navipedia/index.php/Bancroft_Method)
arma::vec bancroft(arma::mat B_pass)
// without travel time rotation
arma::vec rough_bancroft(const arma::mat &B_pass)
{
const int m = B_pass.n_rows;
arma::vec pos = arma::zeros<arma::vec>(4);
for (int iter = 1; iter <= 2; iter++)
{
arma::mat B = B_pass;
const int m = B.n_rows;
for (int i = 0; i < m; i++)
{
double x = B(i, 0);
double y = B(i, 1);
double z = 0;
double traveltime = 0.072;
if (iter == 2)
{
z = B(i, 2);
double rho = std::pow(x - pos(0), 2) + std::pow(y - pos(1), 2) + std::pow(z - pos(2), 2);
traveltime = std::sqrt(rho) / SPEED_OF_LIGHT_M_S;
}
double angle = traveltime * GNSS_OMEGA_EARTH_DOT;
double cosa = std::cos(angle);
double sina = std::sin(angle);
B(i, 0) = cosa * x + sina * y;
B(i, 1) = -sina * x + cosa * y;
}
// We should rotate the matrix accounting for the travel time here,
// but for a rough first estimation we can skip it
arma::mat BBB;
if (m > 4)
{
BBB = arma::inv(B.t() * B) * B.t();
BBB = arma::inv(B_pass.t() * B_pass) * B_pass.t();
}
else
{
BBB = arma::inv(B);
BBB = arma::inv(B_pass);
}
arma::vec e = arma::ones<arma::vec>(m);
arma::vec alpha = arma::zeros<arma::vec>(m);
for (int i = 0; i < m; i++)
{
arma::vec Bi = B.row(i).t();
arma::vec Bi = B_pass.row(i).t();
alpha(i) = lorentz(Bi, Bi) / 2;
}
arma::vec BBBe = BBB * e;
@ -658,7 +640,7 @@ arma::vec bancroft(arma::mat B_pass)
double a = lorentz(BBBe, BBBe);
double b = lorentz(BBBe, BBBalpha) - 1;
double c = lorentz(BBBalpha, BBBalpha);
double root = sqrt(b * b - a * c);
double root = std::sqrt(b * b - a * c);
arma::vec r(2);
r(0) = (-b - root) / a;
r(1) = (-b + root) / a;
@ -674,8 +656,8 @@ arma::vec bancroft(arma::mat B_pass)
for (int i = 0; i < 2; i++)
{
double c_dt = possible_pos(3, i);
double calc = arma::norm(B.row(j).head(3).t() - possible_pos.head_rows(3).col(i)) + c_dt;
double omc = B(j, 3) - calc;
double calc = arma::norm(B_pass.row(j).head(3).t() - possible_pos.head_rows(3).col(i)) + c_dt;
double omc = B_pass(j, 3) - calc;
abs_omc(i) = std::abs(omc);
}
}
@ -738,7 +720,7 @@ int estpos(const obsd_t *obs, int n, const double *rs, const double *dts,
B(i, 2) = rs[2 + i * 6];
B(i, 3) = obs[i].P[0];
}
arma::vec pos = bancroft(B);
arma::vec pos = rough_bancroft(B);
x[0] = pos(0);
x[1] = pos(1);
x[2] = pos(2);