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gps.hh
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#pragma once
#include <bitset>
#include <string>
#include <map>
#include "bits.hh"
#include <iostream>
#include <math.h>
std::basic_string<uint8_t> getCondensedGPSMessage(std::basic_string_view<uint8_t> payload);
struct GPSAlmanac
{
int dataid{-1};
int sv;
uint32_t t0a{0};
uint32_t e{0}, sqrtA{0};
int32_t M0, Omega0, deltai, omega, omegadot;
int health;
int af0, af1;
double getMu() const
{
return 3.986005 * pow(10.0, 14.0);
} // m^3/s^2
// same for galileo & gps
double getOmegaE() const { return 7.2921151467 * pow(10.0, -5.0);} // rad/s
double getE() const
{
return ldexp(e, -21);
}
double getT0e() const
{
return ldexp(t0a, 12);
}
double getI0() const
{
return M_PI*0.3 + ldexp(M_PI*deltai, -19);
}
double getOmegadot() const
{
return ldexp(M_PI * omegadot, -38);
}
double getSqrtA() const
{
return ldexp(sqrtA, -11);
}
double getOmega0() const
{
return ldexp(M_PI * Omega0, -23);
}
double getOmega() const
{
return ldexp(M_PI * omega, -23);
}
double getM0() const
{
return ldexp(M_PI * M0, -23);
}
double getIdot() const { return 0; } // radians/s
double getCic() const { return 0; } // radians
double getCis() const { return 0; } // radians
double getCuc() const { return 0; } // radians
double getCus() const { return 0; } // radians
double getCrc() const { return 0; } // meters
double getCrs() const { return 0; } // meters
double getDeltan()const { return 0; } //radians/s
};
struct GPSState
{
struct SVIOD
{
std::bitset<32> words;
int gnssid;
uint32_t t0e;
uint32_t e, sqrtA;
int32_t m0, omega0, i0, omega, idot, omegadot, deltan;
int16_t cuc{0}, cus{0}, crc{0}, crs{0}, cic{0}, cis{0};
// 16 seconds
uint16_t t0c;
// 2^-31 2^-43
int32_t af0 , af1;
// ???
int8_t af2;
uint32_t wn{0}, tow{0};
double getMu() const
{
return 3.986005 * pow(10.0, 14.0);
} // m^3/s^2
// same for galileo & gps
double getOmegaE() const { return 7.2921151467 * pow(10.0, -5.0);} // rad/s
uint32_t getT0e() const { return t0e; }
double getSqrtA() const { return ldexp(sqrtA, -19); }
double getE() const { return ldexp(e, -33); }
double getCuc() const { return ldexp(cuc, -29); } // radians
double getCus() const { return ldexp(cus, -29); } // radians
double getCrc() const { return ldexp(crc, -5); } // meters
double getCrs() const { return ldexp(crs, -5); } // meters
double getM0() const { return ldexp(m0 * M_PI, -31); } // radians
double getDeltan()const { return ldexp(deltan *M_PI, -43); } //radians/s
double getI0() const { return ldexp(i0 * M_PI, -31); } // radians
double getCic() const { return ldexp(cic, -29); } // radians
double getCis() const { return ldexp(cis, -29); } // radians
double getOmegadot() const { return ldexp(omegadot * M_PI, -43); } // radians/s
double getOmega0() const { return ldexp(omega0 * M_PI, -31); } // radians
double getIdot() const { return ldexp(idot * M_PI, -43); } // radians/s
double getOmega() const { return ldexp(omega * M_PI, -31); } // radians
};
GPSAlmanac gpsalma;
uint8_t gpshealth{0};
uint16_t ai0{0};
int16_t ai1{0}, ai2{0};
int BGDE1E5a{0}, BGDE1E5b{0};
bool disturb1{false}, disturb2{false}, disturb3{false}, disturb4{false}, disturb5{false};
uint16_t wn{0}; // we put the "unrolled" week number here!
uint32_t tow{0}; // "last seen"
//
// 2^-30 2^-50 1 8-bit week
int32_t a0{0}, a1{0}, t0t{0}, wn0t{0};
int32_t a0g{0}, a1g{0}, t0g{0}, wn0g{0};
int8_t dtLS{0}, dtLSF{0};
uint16_t wnLSF{0};
uint8_t dn; // leap second day number
// 1 2^-31 2^-43 2^-55 16 second
int ura, af0, af1, af2, t0c; // GPS parameters that should not be here XXX
int gpsiod{-1};
std::map<int, SVIOD> iods;
SVIOD& getEph(int i) { return iods[i]; } // XXXX gps adaptor
void checkCompleteAndClean(int iod)
{
if(iods[iod].words[2] && iods[iod].words[3]) {
if(iods.size() > 1) {
auto tmp = iods[iod];
iods.clear();
iods[iod] = tmp;
}
}
}
bool isComplete(int iod)
{
return iods[iod].words[2] && iods[iod].words[3];
}
};
template<typename T>
int getT0c(const T& eph)
{
return eph.t0c * 16;
}
template<typename T>
std::pair<double, double> getGPSAtomicOffset(int tow, const T& eph)
{
int delta = ephAge(tow, getT0c(eph));
double cur = eph.af0 + ldexp(delta*eph.af1, -12) + ldexp(delta*delta*eph.af2, -24);
double trend = ldexp(eph.af1, -12) + ldexp(2*delta*eph.af2, -24);
// now in units of 2^-31 seconds, which are 0.5 nanoseconds each
double factor = ldexp(1000000000, -31);
return {factor * cur, factor * trend};
}
template<typename T>
std::pair<double, double> getGPSUTCOffset(int tow, int wn, const T& eph)
{
// 2^-30 2^-50 3600
// a0 a1 t0t
int dw = (int)(uint8_t)wn - (int)(uint8_t) eph.wn0t;
int delta = dw*7*86400 + tow - eph.t0t; // this is pre-scaled for GPS..
double cur = eph.a0 + ldexp(1.0*delta*eph.a1, -20);
double trend = ldexp(eph.a1, -20);
// now in units of 2^-30 seconds, which are ~1.1 nanoseconds each
double factor = ldexp(1000000000, -30);
return {factor * cur, factor * trend};
}
// expects input as 24 bit read to to use messages, returns frame number
template<typename T>
int parseGPSMessage(std::basic_string_view<uint8_t> cond, T& out, uint8_t* pageptr=0)
{
using namespace std;
int frame = getbitu(&cond[0], 24+19, 3);
// 10 * 4 bytes in payload now
out.tow = 1.5*(getbitu(&cond[0], 24, 17)*4);
// cerr << "Preamble: "<<getbitu(&cond[0], 0, 8) <<", frame: "<< frame<<", truncated TOW: "<<out.tow<<endl;
if(frame == 1) {
// word 1, word 2 are TLM and HOW
// 2 bits of padding on each word
// word3:
// 1-10: WN
// 11-12: Which codes 00 = invalid, 01 = P-code on, 10 = C/A code on, 11 invalid
// 13-16: URA, 0-15 scale
// 17-22: 0 is ok
// 23-24: MSB of IODC
// word 8:
// 1-8: LSB of IODC
// 9-24:
out.wn = 2048 + getbitu(&cond[0], 2*24, 10);
out.ura = getbitu(&cond[0], 2*24+12, 4);
out.gpshealth = getbitu(&cond[0], 2*24+16, 6);
// cerr<<"GPS Week Number: "<< out.wn <<", URA: "<< (int)out.ura<<", health: "<<
// (int)out.gpshealth <<endl;
out.af2 = getbits(&cond[0], 8*24, 8); // * 2^-55
out.af1 = getbits(&cond[0], 8*24 + 8, 16); // * 2^-43
out.af0 = getbits(&cond[0], 9*24, 22); // * 2^-31
out.t0c = getbits(&cond[0], 7*24 + 8, 16); // * 16
// cerr<<"t0c*16: "<<out.t0c*16<<", af2: "<< (int)out.af2 <<", af1: "<< out.af1 <<", af0: "<<
// out.af0 <<endl;
}
else if(frame == 2) {
out.gpsiod = getbitu(&cond[0], 2*24, 8);
auto& eph = out.getEph(out.gpsiod);
eph.words[2]=1;
eph.t0e = getbitu(&cond[0], 9*24, 16) * 16.0; // WE SCALE THIS FOR THE USER!!
// cerr<<"IODe "<<(int)iod<<", t0e "<< eph.t0e << " = "<< 16* eph.t0e <<"s"<<endl;
eph.e= getbitu(&cond[0], 5*24+16, 32);
// cerr<<"e: "<<ldexp(eph.e, -33)<<", ";
// sqrt(A), 32 bits, 2^-19
eph.sqrtA= getbitu(&cond[0], 7*24+ 16, 32);
// double sqrtA=ldexp(eph.sqrtA, -19); // 2^-19
// cerr<<"Radius: "<<sqrtA*sqrtA<<endl;
eph.crs = getbits(&cond[0], 2*24 + 8, 16); // 2^-5 meters
eph.deltan = getbits(&cond[0], 3*24, 16); // 2^-43 semi-circles/s
eph.m0 = getbits(&cond[0], 3*24+16, 32); // 2^-31 semi-circles
eph.cuc = getbits(&cond[0], 5*24, 16); // 2^-29 RADIANS
eph.cus = getbits(&cond[0], 7*24, 16); // 2^-29 RADIANS
out.checkCompleteAndClean(out.gpsiod);
}
else if(frame == 3) {
out.gpsiod = getbitu(&cond[0], 9*24, 8);
auto& eph = out.getEph(out.gpsiod);
eph.words[3]=1;
eph.cic = getbits(&cond[0], 2*24, 16); // 2^-29 RADIANS
eph.omega0 = getbits(&cond[0], 2*24 + 16, 32); // 2^-31 semi-circles
eph.cis = getbits(&cond[0], 4*24, 16); // 2^-29 radians
eph.i0 = getbits(&cond[0], 4*24 + 16, 32); // 2^-31, semicircles
eph.crc = getbits(&cond[0], 6*24, 16); // 2^-5, meters
eph.omega = getbits(&cond[0], 6*24+16, 32); // 2^-31, semi-circles
eph.omegadot = getbits(&cond[0], 8*24, 24); // 2^-43, semi-circles/s
eph.idot = getbits(&cond[0], 9*24+8, 14); // 2^-43, semi-cirlces/s
out.checkCompleteAndClean(out.gpsiod);
}
else if(frame == 4) { // this is a carousel frame
int page = getbitu(&cond[0], 2*24 + 2, 6);
if(pageptr)
*pageptr=0;
// cerr<<"Frame 4, page "<<page;
if(page == 56) { // 56 is the new 18 somehow? See table 20-V of the ICD
if(pageptr)
*pageptr=18;
out.a0 = getbits(&cond[0], 6*24 , 32); // 2^-30
out.a1 = getbits(&cond[0], 5*24 , 24); // 2^-50
out.t0t = getbitu(&cond[0], 7*24 + 8, 8) * 4096; // WE SCALE THIS FOR THE USER!
out.wn0t = getbitu(&cond[0], 7*24 + 16, 8);
out.dtLS = getbits(&cond[0], 8*24, 8);
out.dtLSF = getbits(&cond[0], 9*24, 8);
// cerr<<": a0: "<<out.a0<<", a1: "<<out.a1<<", t0t: "<< out.t0t * (1<<12) <<", wn0t: "<< out.wn0t<<", rough offset: "<<ldexp(out.a0, -30)<<endl;
// cerr<<"deltaTLS: "<< (int)out.dtLS<<", post "<< (int)out.dtLSF<<endl;
}
//else cerr<<endl;
// page 18 contains UTC -> 56
// page 25 -> 63
// 2-10 -> 25 -> 32 ??
}
if(frame == 5 || frame==4) { // this is a caroussel frame
out.gpsalma.dataid = getbitu(&cond[0], 2*24, 2);
out.gpsalma.sv = getbitu(&cond[0], 2*24+2, 6);
if(pageptr)
*pageptr= out.gpsalma.sv;
out.gpsalma.e = getbitu(&cond[0], 2*24 + 8, 16);
out.gpsalma.t0a = getbitu(&cond[0], 3*24, 8);
out.gpsalma.deltai = getbits(&cond[0], 3*24 +8 , 16);
out.gpsalma.omegadot = getbits(&cond[0], 4*24, 16);
out.gpsalma.health = getbitu(&cond[0], 4*24 +16, 8);
out.gpsalma.sqrtA = getbitu(&cond[0], 5*24, 24);
out.gpsalma.Omega0 = getbits(&cond[0], 6*24, 24);
out.gpsalma.omega = getbits(&cond[0], 7*24, 24);
out.gpsalma.M0 = getbits(&cond[0], 8*24, 24);
out.gpsalma.af0 = (getbits(&cond[0], 9*24, 8) << 3) + getbits(&cond[0], 9*24 +19, 3);
out.gpsalma.af1 = getbits(&cond[0], 9*24 + 8, 11);
// cerr<<"Frame 5, SV: "<<getbitu(&cond[0], 2*32 + 2 +2, 6)<<endl;
}
return frame;
}