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AP_HAL_SITL: simulate effect of GPS antenna offset

This commit is contained in:
priseborough 2016-10-15 12:07:40 +11:00 committed by Andrew Tridgell
parent 3afe2b1694
commit a9f63abc6f
1 changed files with 40 additions and 5 deletions
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45
libraries/AP_HAL_SITL/sitl_gps.cpp
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@ -963,16 +963,51 @@ void SITL_State::_update_gps(double latitude, double longitude, float altitude,
d.longitude = longitude + glitch_offsets.y;
d.altitude = altitude + glitch_offsets.z;
if (_sitl->gps_drift_alt > 0) {
// slow altitude drift
d.altitude += _sitl->gps_drift_alt*sinf(AP_HAL::millis()*0.001f*0.02f);
}
// Add offet to c.g. velocity to get velocity at antenna
d.speedN = speedN;
d.speedE = speedE;
d.speedD = speedD;
d.have_lock = have_lock;
// correct the latitude, longitude, hiehgt and NED velocity for the offset between
// the vehicle c.g. and GPs antenna
Vector3f posRelOffsetBF = _sitl->gps_pos_offset;
if (!posRelOffsetBF.is_zero()) {
// get a rotation matrix following DCM conventions (body to earth)
Matrix3f rotmat;
rotmat.from_euler(radians(_sitl->state.rollDeg),
radians(_sitl->state.pitchDeg),
radians(_sitl->state.yawDeg));
// rotate the antenna offset into the earth frame
Vector3f posRelOffsetEF = rotmat * posRelOffsetBF;
// Add the offset to the latitude, longitude and height using a spherical earth approximation
double const earth_rad_inv = 1.569612305760477e-7; // use Authalic/Volumetric radius
double lng_scale_factor = earth_rad_inv / cos(radians(d.latitude));
d.latitude += degrees(posRelOffsetEF.x * earth_rad_inv);
d.longitude += degrees(posRelOffsetEF.y * lng_scale_factor);
d.altitude -= posRelOffsetEF.z;
// calculate a velocity offset due to the antenna position offset and body rotation rate
// note: % operator is overloaded for cross product
Vector3f gyro(radians(_sitl->state.rollRate),
radians(_sitl->state.pitchRate),
radians(_sitl->state.yawRate));
Vector3f velRelOffsetBF = gyro % posRelOffsetBF;
// rotate the velocity offset into earth frame and add to the c.g. velocity
Vector3f velRelOffsetEF = rotmat * velRelOffsetBF;
d.speedN += velRelOffsetEF.x;
d.speedE += velRelOffsetEF.y;
d.speedD += velRelOffsetEF.z;
}
if (_sitl->gps_drift_alt > 0) {
// slow altitude drift
d.altitude += _sitl->gps_drift_alt*sinf(AP_HAL::millis()*0.001f*0.02f);
}
// add in some GPS lag
_gps_data[next_gps_index++] = d;
if (next_gps_index >= gps_delay+1) {