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ardupilot/libraries/AP_Compass/CompassCalibrator.cpp

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/// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
* The intention of a magnetometer in a compass application is to measure
* Earth's magnetic field. Measurements other than those of Earth's magnetic
* field are considered errors. This algorithm computes a set of correction
* parameters that null out errors from various sources:
*
* - Sensor bias error
* - "Hard iron" error caused by materials fixed to the vehicle body that
* produce static magnetic fields.
* - Sensor scale-factor error
* - Sensor cross-axis sensitivity
* - "Soft iron" error caused by materials fixed to the vehicle body that
* distort magnetic fields.
*
* This is done by taking a set of samples that are assumed to be the product
* of rotation in earth's magnetic field and fitting an offset ellipsoid to
* them, determining the correction to be applied to adjust the samples into an
* origin-centered sphere.
*
* The state machine of this library is described entirely by the
* compass_cal_status_t enum, and all state transitions are managed by the
* set_status function. Normally, the library is in the NOT_STARTED state. When
* the start function is called, the state transitions to WAITING_TO_START,
* until two conditions are met: the delay as elapsed, and the memory for the
* sample buffer has been successfully allocated.
* Once these conditions are met, the state transitions to RUNNING_STEP_ONE, and
* samples are collected via calls to the new_sample function. These samples are
* accepted or rejected based on distance to the nearest sample. The samples are
* assumed to cover the surface of a sphere, and the radius of that sphere is
* initialized to a conservative value. Based on a circle-packing pattern, the
* minimum distance is set such that some percentage of the surface of that
* sphere must be covered by samples.
*
* Once the sample buffer is full, a sphere fitting algorithm is run, which
* computes a new sphere radius. The sample buffer is thinned of samples which
* no longer meet the acceptance criteria, and the state transitions to
* RUNNING_STEP_TWO. Samples continue to be collected until the buffer is full
* again, the full ellipsoid fit is run, and the state transitions to either
* SUCCESS or FAILED.
*
* The fitting algorithm used is Levenberg-Marquardt. See also:
* http://en.wikipedia.org/wiki/Levenberg%E2%80%93Marquardt_algorithm
*/
#include "CompassCalibrator.h"
#include <AP_HAL/AP_HAL.h>
extern const AP_HAL::HAL& hal;
////////////////////////////////////////////////////////////
///////////////////// PUBLIC INTERFACE /////////////////////
////////////////////////////////////////////////////////////
CompassCalibrator::CompassCalibrator():
_tolerance(COMPASS_CAL_DEFAULT_TOLERANCE),
_sample_buffer(NULL)
{
clear();
}
void CompassCalibrator::clear() {
set_status(COMPASS_CAL_NOT_STARTED);
}
void CompassCalibrator::start(bool retry, bool autosave, float delay) {
if(running()) {
return;
}
_autosave = autosave;
_attempt = 1;
_retry = retry;
_delay_start_sec = delay;
_start_time_ms = AP_HAL::millis();
set_status(COMPASS_CAL_WAITING_TO_START);
}
void CompassCalibrator::get_calibration(Vector3f &offsets, Vector3f &diagonals, Vector3f &offdiagonals) {
if (_status != COMPASS_CAL_SUCCESS) {
return;
}
offsets = _params.offset;
diagonals = _params.diag;
offdiagonals = _params.offdiag;
}
float CompassCalibrator::get_completion_percent() const {
// first sampling step is 1/3rd of the progress bar
// never return more than 99% unless _status is COMPASS_CAL_SUCCESS
switch(_status) {
case COMPASS_CAL_NOT_STARTED:
case COMPASS_CAL_WAITING_TO_START:
return 0.0f;
case COMPASS_CAL_RUNNING_STEP_ONE:
return 33.3f * _samples_collected/COMPASS_CAL_NUM_SAMPLES;
case COMPASS_CAL_RUNNING_STEP_TWO:
return 33.3f + 65.7f*((float)(_samples_collected-_samples_thinned)/(COMPASS_CAL_NUM_SAMPLES-_samples_thinned));
case COMPASS_CAL_SUCCESS:
return 100.0f;
case COMPASS_CAL_FAILED:
default:
return 0.0f;
};
}
bool CompassCalibrator::check_for_timeout() {
uint32_t tnow = AP_HAL::millis();
if(running() && tnow - _last_sample_ms > 1000) {
_retry = false;
set_status(COMPASS_CAL_FAILED);
return true;
}
return false;
}
void CompassCalibrator::new_sample(const Vector3f& sample) {
_last_sample_ms = AP_HAL::millis();
if(_status == COMPASS_CAL_WAITING_TO_START) {
set_status(COMPASS_CAL_RUNNING_STEP_ONE);
}
if(running() && _samples_collected < COMPASS_CAL_NUM_SAMPLES && accept_sample(sample)) {
_sample_buffer[_samples_collected].set(sample);
_samples_collected++;
}
}
void CompassCalibrator::update(bool &failure) {
failure = false;
if(!fitting()) {
return;
}
if(_status == COMPASS_CAL_RUNNING_STEP_ONE) {
if (_fit_step >= 10) {
if(is_equal(_fitness,_initial_fitness) || isnan(_fitness)) { //if true, means that fitness is diverging instead of converging
set_status(COMPASS_CAL_FAILED);
failure = true;
}
set_status(COMPASS_CAL_RUNNING_STEP_TWO);
} else {
run_sphere_fit();
_fit_step++;
}
} else if(_status == COMPASS_CAL_RUNNING_STEP_TWO) {
if (_fit_step >= 35) {
if(fit_acceptable()) {
set_status(COMPASS_CAL_SUCCESS);
} else {
set_status(COMPASS_CAL_FAILED);
failure = true;
}
} else if (_fit_step < 15) {
run_sphere_fit();
_fit_step++;
} else {
run_ellipsoid_fit();
_fit_step++;
}
}
}
/////////////////////////////////////////////////////////////
////////////////////// PRIVATE METHODS //////////////////////
/////////////////////////////////////////////////////////////
bool CompassCalibrator::running() const {
return _status == COMPASS_CAL_RUNNING_STEP_ONE || _status == COMPASS_CAL_RUNNING_STEP_TWO;
}
bool CompassCalibrator::fitting() const {
return running() && _samples_collected == COMPASS_CAL_NUM_SAMPLES;
}
void CompassCalibrator::initialize_fit() {
//initialize _fitness before starting a fit
if (_samples_collected != 0) {
_fitness = calc_mean_squared_residuals(_params);
} else {
_fitness = 1.0e30f;
}
_ellipsoid_lambda = 1.0f;
_sphere_lambda = 1.0f;
_initial_fitness = _fitness;
_fit_step = 0;
}
void CompassCalibrator::reset_state() {
_samples_collected = 0;
_samples_thinned = 0;
_params.radius = 200;
_params.offset.zero();
_params.diag = Vector3f(1.0f,1.0f,1.0f);
_params.offdiag.zero();
initialize_fit();
}
bool CompassCalibrator::set_status(compass_cal_status_t status) {
if (status != COMPASS_CAL_NOT_STARTED && _status == status) {
return true;
}
switch(status) {
case COMPASS_CAL_NOT_STARTED:
reset_state();
_status = COMPASS_CAL_NOT_STARTED;
if(_sample_buffer != NULL) {
free(_sample_buffer);
_sample_buffer = NULL;
}
return true;
case COMPASS_CAL_WAITING_TO_START:
reset_state();
_status = COMPASS_CAL_WAITING_TO_START;
set_status(COMPASS_CAL_RUNNING_STEP_ONE);
return true;
case COMPASS_CAL_RUNNING_STEP_ONE:
if(_status != COMPASS_CAL_WAITING_TO_START) {
return false;
}
if(_attempt == 1 && (AP_HAL::millis()-_start_time_ms)*1.0e-3f < _delay_start_sec) {
return false;
}
if (_sample_buffer == NULL) {
_sample_buffer =
(CompassSample*) malloc(sizeof(CompassSample) *
COMPASS_CAL_NUM_SAMPLES);
}
if(_sample_buffer != NULL) {
initialize_fit();
_status = COMPASS_CAL_RUNNING_STEP_ONE;
return true;
}
return false;
case COMPASS_CAL_RUNNING_STEP_TWO:
if(_status != COMPASS_CAL_RUNNING_STEP_ONE) {
return false;
}
thin_samples();
initialize_fit();
_status = COMPASS_CAL_RUNNING_STEP_TWO;
return true;
case COMPASS_CAL_SUCCESS:
if(_status != COMPASS_CAL_RUNNING_STEP_TWO) {
return false;
}
if(_sample_buffer != NULL) {
free(_sample_buffer);
_sample_buffer = NULL;
}
_status = COMPASS_CAL_SUCCESS;
return true;
case COMPASS_CAL_FAILED:
if(_status == COMPASS_CAL_NOT_STARTED) {
return false;
}
if(_retry && set_status(COMPASS_CAL_WAITING_TO_START)) {
_attempt++;
return true;
}
if(_sample_buffer != NULL) {
free(_sample_buffer);
_sample_buffer = NULL;
}
_status = COMPASS_CAL_FAILED;
return true;
default:
return false;
};
}
bool CompassCalibrator::fit_acceptable() {
if( !isnan(_fitness) &&
_params.radius > 150 && _params.radius < 950 && //Earth's magnetic field strength range: 250-850mG
fabsf(_params.offset.x) < 1000 &&
fabsf(_params.offset.y) < 1000 &&
fabsf(_params.offset.z) < 1000 &&
_params.diag.x > 0.2f && _params.diag.x < 5.0f &&
_params.diag.y > 0.2f && _params.diag.y < 5.0f &&
_params.diag.z > 0.2f && _params.diag.z < 5.0f &&
fabsf(_params.offdiag.x) < 1.0f && //absolute of sine/cosine output cannot be greater than 1
fabsf(_params.offdiag.y) < 1.0f &&
fabsf(_params.offdiag.z) < 1.0f ){
return _fitness <= sq(_tolerance);
}
return false;
}
void CompassCalibrator::thin_samples() {
if(_sample_buffer == NULL) {
return;
}
_samples_thinned = 0;
// shuffle the samples http://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
// this is so that adjacent samples don't get sequentially eliminated
for(uint16_t i=_samples_collected-1; i>=1; i--) {
uint16_t j = get_random() % (i+1);
CompassSample temp = _sample_buffer[i];
_sample_buffer[i] = _sample_buffer[j];
_sample_buffer[j] = temp;
}
for(uint16_t i=0; i < _samples_collected; i++) {
if(!accept_sample(_sample_buffer[i])) {
_sample_buffer[i] = _sample_buffer[_samples_collected-1];
_samples_collected --;
_samples_thinned ++;
}
}
}
/*
* The sample acceptance distance is determined as follows:
* For any regular polyhedron with triangular faces, the angle theta subtended
* by two closest points is defined as
*
* theta = arccos(cos(A)/(1-cos(A)))
*
* Where:
* A = (4pi/F + pi)/3
* and
* F = 2V - 4 is the number of faces for the polyhedron in consideration,
* which depends on the number of vertices V
*
* The above equation was proved after solving for spherical triangular excess
* and related equations.
*/
bool CompassCalibrator::accept_sample(const Vector3f& sample)
{
static const uint16_t faces = (2 * COMPASS_CAL_NUM_SAMPLES - 4);
static const float a = (4.0f * M_PI / (3.0f * faces)) + M_PI / 3.0f;
static const float theta = 0.5f * acosf(cosf(a) / (1.0f - cosf(a)));
if(_sample_buffer == NULL) {
return false;
}
float min_distance = _params.radius * 2*sinf(theta/2);
for (uint16_t i = 0; i<_samples_collected; i++){
float distance = (sample - _sample_buffer[i].get()).length();
if(distance < min_distance) {
return false;
}
}
return true;
}
bool CompassCalibrator::accept_sample(const CompassSample& sample) {
return accept_sample(sample.get());
}
float CompassCalibrator::calc_residual(const Vector3f& sample, const param_t& params) const {
Matrix3f softiron(
params.diag.x , params.offdiag.x , params.offdiag.y,
params.offdiag.x , params.diag.y , params.offdiag.z,
params.offdiag.y , params.offdiag.z , params.diag.z
);
return params.radius - (softiron*(sample+params.offset)).length();
}
float CompassCalibrator::calc_mean_squared_residuals() const
{
return calc_mean_squared_residuals(_params);
}
float CompassCalibrator::calc_mean_squared_residuals(const param_t& params) const
{
if(_sample_buffer == NULL || _samples_collected == 0) {
return 1.0e30f;
}
float sum = 0.0f;
for(uint16_t i=0; i < _samples_collected; i++){
Vector3f sample = _sample_buffer[i].get();
float resid = calc_residual(sample, params);
sum += sq(resid);
}
sum /= _samples_collected;
return sum;
}
void CompassCalibrator::calc_sphere_jacob(const Vector3f& sample, const param_t& params, float* ret) const{
const Vector3f &offset = params.offset;
const Vector3f &diag = params.diag;
const Vector3f &offdiag = params.offdiag;
Matrix3f softiron(
diag.x , offdiag.x , offdiag.y,
offdiag.x , diag.y , offdiag.z,
offdiag.y , offdiag.z , diag.z
);
float A = (diag.x * (sample.x + offset.x)) + (offdiag.x * (sample.y + offset.y)) + (offdiag.y * (sample.z + offset.z));
float B = (offdiag.x * (sample.x + offset.x)) + (diag.y * (sample.y + offset.y)) + (offdiag.z * (sample.z + offset.z));
float C = (offdiag.y * (sample.x + offset.x)) + (offdiag.z * (sample.y + offset.y)) + (diag.z * (sample.z + offset.z));
float length = (softiron*(sample+offset)).length();
// 0: partial derivative (radius wrt fitness fn) fn operated on sample
ret[0] = 1.0f;
// 1-3: partial derivative (offsets wrt fitness fn) fn operated on sample
ret[1] = -1.0f * (((diag.x * A) + (offdiag.x * B) + (offdiag.y * C))/length);
ret[2] = -1.0f * (((offdiag.x * A) + (diag.y * B) + (offdiag.z * C))/length);
ret[3] = -1.0f * (((offdiag.y * A) + (offdiag.z * B) + (diag.z * C))/length);
}
void CompassCalibrator::run_sphere_fit()
{
if(_sample_buffer == NULL) {
return;
}
const float lma_damping = 10.0f;
float fitness = _fitness;
float fit1, fit2;
param_t fit1_params, fit2_params;
fit1_params = fit2_params = _params;
float JTJ[COMPASS_CAL_NUM_SPHERE_PARAMS*COMPASS_CAL_NUM_SPHERE_PARAMS];
float JTJ2[COMPASS_CAL_NUM_SPHERE_PARAMS*COMPASS_CAL_NUM_SPHERE_PARAMS];
float JTFI[COMPASS_CAL_NUM_SPHERE_PARAMS];
memset(&JTJ,0,sizeof(JTJ));
memset(&JTJ2,0,sizeof(JTJ2));
memset(&JTFI,0,sizeof(JTFI));
// Gauss Newton Part common for all kind of extensions including LM
for(uint16_t k = 0; k<_samples_collected; k++) {
Vector3f sample = _sample_buffer[k].get();
float sphere_jacob[COMPASS_CAL_NUM_SPHERE_PARAMS];
calc_sphere_jacob(sample, fit1_params, sphere_jacob);
for(uint8_t i = 0;i < COMPASS_CAL_NUM_SPHERE_PARAMS; i++) {
// compute JTJ
for(uint8_t j = 0; j < COMPASS_CAL_NUM_SPHERE_PARAMS; j++) {
JTJ[i*COMPASS_CAL_NUM_SPHERE_PARAMS+j] += sphere_jacob[i] * sphere_jacob[j];
JTJ2[i*COMPASS_CAL_NUM_SPHERE_PARAMS+j] += sphere_jacob[i] * sphere_jacob[j]; //a backup JTJ for LM
}
// compute JTFI
JTFI[i] += sphere_jacob[i] * calc_residual(sample, fit1_params);
}
}
//------------------------Levenberg-Marquardt-part-starts-here---------------------------------//
//refer: http://en.wikipedia.org/wiki/Levenberg%E2%80%93Marquardt_algorithm#Choice_of_damping_parameter
for(uint8_t i = 0; i < COMPASS_CAL_NUM_SPHERE_PARAMS; i++) {
JTJ[i*COMPASS_CAL_NUM_SPHERE_PARAMS+i] += _sphere_lambda;
JTJ2[i*COMPASS_CAL_NUM_SPHERE_PARAMS+i] += _sphere_lambda/lma_damping;
}
if(!inverse(JTJ, JTJ, 4)) {
return;
}
if(!inverse(JTJ2, JTJ2, 4)) {
return;
}
for(uint8_t row=0; row < COMPASS_CAL_NUM_SPHERE_PARAMS; row++) {
for(uint8_t col=0; col < COMPASS_CAL_NUM_SPHERE_PARAMS; col++) {
fit1_params.get_sphere_params()[row] -= JTFI[col] * JTJ[row*COMPASS_CAL_NUM_SPHERE_PARAMS+col];
fit2_params.get_sphere_params()[row] -= JTFI[col] * JTJ2[row*COMPASS_CAL_NUM_SPHERE_PARAMS+col];
}
}
fit1 = calc_mean_squared_residuals(fit1_params);
fit2 = calc_mean_squared_residuals(fit2_params);
if(fit1 > _fitness && fit2 > _fitness){
_sphere_lambda *= lma_damping;
} else if(fit2 < _fitness && fit2 < fit1) {
_sphere_lambda /= lma_damping;
fit1_params = fit2_params;
fitness = fit2;
} else if(fit1 < _fitness){
fitness = fit1;
}
//--------------------Levenberg-Marquardt-part-ends-here--------------------------------//
if(!isnan(fitness) && fitness < _fitness) {
_fitness = fitness;
_params = fit1_params;
}
}
void CompassCalibrator::calc_ellipsoid_jacob(const Vector3f& sample, const param_t& params, float* ret) const{
const Vector3f &offset = params.offset;
const Vector3f &diag = params.diag;
const Vector3f &offdiag = params.offdiag;
Matrix3f softiron(
diag.x , offdiag.x , offdiag.y,
offdiag.x , diag.y , offdiag.z,
offdiag.y , offdiag.z , diag.z
);
float A = (diag.x * (sample.x + offset.x)) + (offdiag.x * (sample.y + offset.y)) + (offdiag.y * (sample.z + offset.z));
float B = (offdiag.x * (sample.x + offset.x)) + (diag.y * (sample.y + offset.y)) + (offdiag.z * (sample.z + offset.z));
float C = (offdiag.y * (sample.x + offset.x)) + (offdiag.z * (sample.y + offset.y)) + (diag.z * (sample.z + offset.z));
float length = (softiron*(sample+offset)).length();
// 0-2: partial derivative (offset wrt fitness fn) fn operated on sample
ret[0] = -1.0f * (((diag.x * A) + (offdiag.x * B) + (offdiag.y * C))/length);
ret[1] = -1.0f * (((offdiag.x * A) + (diag.y * B) + (offdiag.z * C))/length);
ret[2] = -1.0f * (((offdiag.y * A) + (offdiag.z * B) + (diag.z * C))/length);
// 3-5: partial derivative (diag offset wrt fitness fn) fn operated on sample
ret[3] = -1.0f * ((sample.x + offset.x) * A)/length;
ret[4] = -1.0f * ((sample.y + offset.y) * B)/length;
ret[5] = -1.0f * ((sample.z + offset.z) * C)/length;
// 6-8: partial derivative (off-diag offset wrt fitness fn) fn operated on sample
ret[6] = -1.0f * (((sample.y + offset.y) * A) + ((sample.x + offset.x) * B))/length;
ret[7] = -1.0f * (((sample.z + offset.z) * A) + ((sample.x + offset.x) * C))/length;
ret[8] = -1.0f * (((sample.z + offset.z) * B) + ((sample.y + offset.y) * C))/length;
}
void CompassCalibrator::run_ellipsoid_fit()
{
if(_sample_buffer == NULL) {
return;
}
const float lma_damping = 10.0f;
float fitness = _fitness;
float fit1, fit2;
param_t fit1_params, fit2_params;
fit1_params = fit2_params = _params;
float JTJ[COMPASS_CAL_NUM_ELLIPSOID_PARAMS*COMPASS_CAL_NUM_ELLIPSOID_PARAMS];
float JTJ2[COMPASS_CAL_NUM_ELLIPSOID_PARAMS*COMPASS_CAL_NUM_ELLIPSOID_PARAMS];
float JTFI[COMPASS_CAL_NUM_ELLIPSOID_PARAMS];
memset(&JTJ,0,sizeof(JTJ));
memset(&JTJ2,0,sizeof(JTJ2));
memset(&JTFI,0,sizeof(JTFI));
// Gauss Newton Part common for all kind of extensions including LM
for(uint16_t k = 0; k<_samples_collected; k++) {
Vector3f sample = _sample_buffer[k].get();
float ellipsoid_jacob[COMPASS_CAL_NUM_ELLIPSOID_PARAMS];
calc_ellipsoid_jacob(sample, fit1_params, ellipsoid_jacob);
for(uint8_t i = 0;i < COMPASS_CAL_NUM_ELLIPSOID_PARAMS; i++) {
// compute JTJ
for(uint8_t j = 0; j < COMPASS_CAL_NUM_ELLIPSOID_PARAMS; j++) {
JTJ [i*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+j] += ellipsoid_jacob[i] * ellipsoid_jacob[j];
JTJ2[i*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+j] += ellipsoid_jacob[i] * ellipsoid_jacob[j];
}
// compute JTFI
JTFI[i] += ellipsoid_jacob[i] * calc_residual(sample, fit1_params);
}
}
//------------------------Levenberg-Marquardt-part-starts-here---------------------------------//
//refer: http://en.wikipedia.org/wiki/Levenberg%E2%80%93Marquardt_algorithm#Choice_of_damping_parameter
for(uint8_t i = 0; i < COMPASS_CAL_NUM_ELLIPSOID_PARAMS; i++) {
JTJ[i*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+i] += _ellipsoid_lambda;
JTJ2[i*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+i] += _ellipsoid_lambda/lma_damping;
}
if(!inverse(JTJ, JTJ, 9)) {
return;
}
if(!inverse(JTJ2, JTJ2, 9)) {
return;
}
for(uint8_t row=0; row < COMPASS_CAL_NUM_ELLIPSOID_PARAMS; row++) {
for(uint8_t col=0; col < COMPASS_CAL_NUM_ELLIPSOID_PARAMS; col++) {
fit1_params.get_ellipsoid_params()[row] -= JTFI[col] * JTJ[row*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+col];
fit2_params.get_ellipsoid_params()[row] -= JTFI[col] * JTJ2[row*COMPASS_CAL_NUM_ELLIPSOID_PARAMS+col];
}
}
fit1 = calc_mean_squared_residuals(fit1_params);
fit2 = calc_mean_squared_residuals(fit2_params);
if(fit1 > _fitness && fit2 > _fitness){
_ellipsoid_lambda *= lma_damping;
} else if(fit2 < _fitness && fit2 < fit1) {
_ellipsoid_lambda /= lma_damping;
fit1_params = fit2_params;
fitness = fit2;
} else if(fit1 < _fitness){
fitness = fit1;
}
//--------------------Levenberg-part-ends-here--------------------------------//
if(fitness < _fitness) {
_fitness = fitness;
_params = fit1_params;
}
}
uint16_t CompassCalibrator::get_random(void)
{
static uint32_t m_z = 1234;
static uint32_t m_w = 76542;
m_z = 36969 * (m_z & 65535) + (m_z >> 16);
m_w = 18000 * (m_w & 65535) + (m_w >> 16);
return ((m_z << 16) + m_w) & 0xFFFF;
}
//////////////////////////////////////////////////////////
//////////// CompassSample public interface //////////////
//////////////////////////////////////////////////////////
Vector3f CompassCalibrator::CompassSample::get() const {
Vector3f out;
out.x = (float)x*2048.0f/32700.0f;
out.y = (float)y*2048.0f/32700.0f;
out.z = (float)z*2048.0f/32700.0f;
return out;
}
void CompassCalibrator::CompassSample::set(const Vector3f &in) {
x = (int16_t)(in.x*32700.0f/2048.0f + 0.5f);
y = (int16_t)(in.y*32700.0f/2048.0f + 0.5f);
z = (int16_t)(in.z*32700.0f/2048.0f + 0.5f);
}
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