Index: trunk/BNC/src/bnchelp.html =================================================================== --- trunk/BNC/src/bnchelp.html (revision 11060) +++ trunk/BNC/src/bnchelp.html (revision 11061) @@ -7843,4 +7843,43 @@ - despite the fact, that the delivered code biases of an AC may contain contributions from other biases, also phase biases. +

+

+ Consistency of code biases and clocks: + This procedure requires that the code biases of an AC are consistent with its clocks. An AC is free to estimate + its clocks from signals other than the reference signals; its code biases of the reference signals must then + refer to exactly these clocks, i.e. they have to be estimated together with them or aligned to the same clock + datum. If an AC combines its clocks with code biases from another source (e.g. a SINEX Bias file of another + analysis), the ionosphere-free linear combination B_IF of these biases does not belong to the clocks. The clocks + are then shifted per satellite by the wrong amount before the combination. +

+

+ In the combination (method 'Filter') such errors are absorbed by the satellite-specific clock offsets estimated + for each AC, which consequently follow B_IF of that AC from satellite to satellite. BNC uses this to check the + consistency, separately for each AC and system: +

+ +

+ The result of each positive check is written to the combination logfile, a warning to the BNC logfile at most once + per hour per AC and system, e.g. +

+ 
+bncComb: BKG E code biases (C1C/C5Q) seem inconsistent with its clocks: satellite offsets follow the bias
+combination B_IF (27 satellites, B_IF spread 0.084 m, slope 0.60, correlation 0.88)
+
+

+ The AC is still used in the combination, its offsets absorb most of the error. Nevertheless, the code biases + sent out by this AC should be corrected by its provider: either biases estimated together with the clocks + should be used, or the external biases have to be aligned to the clocks per satellite (b' = b - B_IF of the + reference signals, SSR sign convention). The check is not applied with the 'Single-Epoch' method.

Index: trunk/BNC/src/combination/bnccomb.cpp =================================================================== --- trunk/BNC/src/combination/bnccomb.cpp (revision 11060) +++ trunk/BNC/src/combination/bnccomb.cpp (revision 11061) @@ -899,4 +899,10 @@ _newCorr->_satCodeBiasIF += codeCoeff * codeBiasesRefSig[frqType]; } + if (codeBiasesRefSig.size() == 2) { + _acBiasIF[acName][prnStr.mid(0,3)] = _newCorr->_satCodeBiasIF; + } + else { + _acBiasIF[acName].remove(prnStr.mid(0,3)); + } _newCorr->_satCodeBias._bias.clear(); } @@ -1079,4 +1085,7 @@ out.flush(); } + if (_method == filter) { + checkBiasConsistency(epoTime, sys, out); + } printResults(epoTime, out, masterCorr); dumpResults(epoTime, masterCorr); @@ -1144,5 +1153,5 @@ if (pp->type == cmbParam::offACSat && pp->AC == corrs(sys)[maxResIndex-1]->_acName && - pp->prn == corrs(sys)[maxResIndex-1]->_prn.mid(0,3)) { + pp->prn == corrs(sys)[maxResIndex-1]->_prn) { QQ_sav.Row(iPar) = 0.0; QQ_sav.Column(iPar) = 0.0; @@ -1174,4 +1183,105 @@ return success; +} + +// Check the consistency of the AC code biases with the AC clocks +//////////////////////////////////////////////////////////////////////////// +// An AC's clocks refer to its own clock signals; the code biases of the +// reference signals refer them to the reference signals (B_IF, ionosphere- +// free combination of these biases, added to the AC clocks). If the code +// biases do not belong to the clocks (e.g. taken from another product), the +// error B_IF is absorbed by the AC's satellite offsets. The satellite offsets +// of each AC are therefore regressed against its B_IF every 5 minutes (from +// 5 minutes after the start); a warning is issued (at most once per hour per +// AC and system) if B_IF varies noticeably between the satellites and the +// offsets clearly follow it. +//////////////////////////////////////////////////////////////////////////// +void bncComb::checkBiasConsistency(bncTime epoTime, char sys, QTextStream& out) { + + const double CHECK_INT = 300.0; // [s] check interval, first check after start + const unsigned MIN_SAT = 5; + const double MIN_SPREAD = 0.03; // [m] minimum std. deviation of B_IF + const double MIN_SLOPE = 0.3; // 0.5 expected for 2 ACs, -> 1 for more ACs + const double MIN_CORR = 0.7; + + if (!_biasCheckStart[sys].valid()) { + _biasCheckStart[sys] = epoTime; + _biasCheckLast[sys] = epoTime; + return; + } + if (epoTime - _biasCheckLast[sys] < CHECK_INT) { + return; + } + _biasCheckLast[sys] = epoTime; + + QListIterator itAc(_ACs); + while (itAc.hasNext()) { + const QString& acName = itAc.next()->name; + if (!_acBiasIF.contains(acName)) { + continue; + } + const QMap& biasIF = _acBiasIF[acName]; + + // satellites of this AC in the current epoch with B_IF available + QVector xx, yy; + for (int ii = 0; ii < corrs(sys).size(); ii++) { + const cmbCorr* corr = corrs(sys)[ii]; + if (corr->_acName != acName || !biasIF.contains(corr->_prn.mid(0,3))) { + continue; + } + for (int iPar = 1; iPar <= _params[sys].size(); iPar++) { + const cmbParam* pp = _params[sys][iPar-1]; + if (pp->type == cmbParam::offACSat && pp->AC == acName && pp->prn == corr->_prn) { + xx.push_back(biasIF[corr->_prn.mid(0,3)]); + yy.push_back(pp->xx); + break; + } + } + } + unsigned nn = xx.size(); + if (nn < MIN_SAT) { + continue; + } + double mx = 0.0, my = 0.0; + for (unsigned ii = 0; ii < nn; ii++) { + mx += xx[ii] / nn; + my += yy[ii] / nn; + } + double sxx = 0.0, syy = 0.0, sxy = 0.0; + for (unsigned ii = 0; ii < nn; ii++) { + sxx += (xx[ii] - mx) * (xx[ii] - mx); + syy += (yy[ii] - my) * (yy[ii] - my); + sxy += (xx[ii] - mx) * (yy[ii] - my); + } + double spread = sqrt(sxx / nn); + if (spread < MIN_SPREAD || syy <= 0.0) { + continue; + } + double slope = sxy / sxx; + double corrCoeff = sxy / sqrt(sxx * syy); + if (slope < MIN_SLOPE || corrCoeff < MIN_CORR) { + continue; + } + + QString refSig; + for (unsigned ii = 1; ii < cmbRefSig::cIF; ii++) { + t_frequency::type frqType = cmbRefSig::toFreq(sys, static_cast(ii)); + refSig += QString("%1C%2%3").arg(ii > 1 ? "/" : "").arg(t_frequency::toString(frqType)[1]) + .arg(cmbRefSig::toAttrib(sys, static_cast(ii))); + } + QString msg = QString("%1 %2 code biases (%3) seem inconsistent with its clocks: " + "satellite offsets follow the bias combination B_IF " + "(%4 satellites, B_IF spread %5 m, slope %6, correlation %7)") + .arg(acName).arg(sys).arg(refSig).arg(nn) + .arg(spread, 0, 'f', 3).arg(slope, 0, 'f', 2).arg(corrCoeff, 0, 'f', 2); + out << epoTime.datestr().c_str() << " " << epoTime.timestr().c_str() + << " " << msg << "\n"; + QString key = acName + sys; + bncTime& warned = _biasCheckWarned[key]; + if (!warned.valid() || epoTime - warned >= 3600.0) { + warned = epoTime; + emit newMessage("bncComb: " + msg.toLatin1(), true); + } + } } Index: trunk/BNC/src/combination/bnccomb.h =================================================================== --- trunk/BNC/src/combination/bnccomb.h (revision 11060) +++ trunk/BNC/src/combination/bnccomb.h (revision 11061) @@ -270,4 +270,9 @@ QMap _refBiasWarned; // last warning per AC and system QMap _singleACWarned; // last 'fewer than 2 ACs' message per system + QMap > _acBiasIF; // latest B_IF of the reference signals per AC and satellite + QMap _biasCheckStart; // first combined epoch per system + QMap _biasCheckLast; // last bias/clock consistency check per system + QMap _biasCheckWarned; // last inconsistency warning per AC and system + void checkBiasConsistency(bncTime epoTime, char sys, QTextStream& out); bool allACsBeyond(const bncTime& epoTime) const; bncTime _resTime;