Re: [Paparazzi-devel] Altitude estimation wiht BMP-sensor

[Rolf Noellenburg]

Hello Heinrich,

I'm using a SPC1000 for hight detection and had the same problems.
I did the following, but there might have been an easier way(?):
First I copied and renamed the bar_scp-files and modifyied the resulting 
baro_scp_rn.c-file according to baro_ets-files in order to receive a 
hight in addition to the pressure and temp.
Like you experienced, some mixing of Baro and GPS altitude occured the 
estimator.c (line 216 - 219):

**********
#ifndef USE_BARO_ETS
  float falt = gps.hmsl / 1000.;
  EstimatorSetAlt(falt);
#endif
**********

So I changed line 216 to

**********
#ifndef USE_BARO_SCP_RN
//probably better way: #ifndef USE_BARO_ETS || USE_BARO_SCP_RN
**********

The delay of the varo versus GPS altitude happes because of unmatched 
Kalman values. If no modification of the estmator.c is done, it looks 
like this (line 149 - 166):

**********
#ifdef USE_BARO_MS5534A
  if (alt_baro_enabled) {
    DT = BARO_DT;
    R = baro_MS5534A_r;
    SIGMA2 = baro_MS5534A_sigma2;
  } else
#elif defined(USE_BARO_ETS)
  if (baro_ets_enabled) {
    DT = BARO_ETS_DT;
    R = baro_ets_r;
    SIGMA2 = baro_ets_sigma2;
  } else
#endif
  {
    DT = GPS_DT;
    R = GPS_R;
    SIGMA2 = GPS_SIGMA2;
  }
**********

I added the following:

**********
#elif defined(USE_BARO_SCP_RN)
  if (baro_scp_enabled) {
    DT = BARO_SCP_DT;
    R = baro_scp_r;
    SIGMA2 = baro_scp_sigma2;
**********

So I had to add in the baro_scp_rn.h (I'm using the 9Hz mode):
#define BARO_SCP_DT .1111

and in the baro_scp_rn.c:
#define BARO_SCP_R .01
#define BARO_SCP_SIGMA2 1

With this changes I'm getting rather noisy but quick z and z_dots out of 
the estimator.

Hope this were all the changes I did and that it helps.

Regards,
Rolf