NMEAgps + ublox ... how to get latitude, longitude, speed and course errors?

Hi folks,

I'm currently a ublox 8 board with Arduino Mega 2560. Everything works great except for the following:

fix.lat_err_cm, fix.lon_err_cm and fix.alt_err_cm, in integer centimeters
fix.spd_err_mmps, in integer mm/s
fix.hdg_errE5, in integer degrees * 100000
fix.time_err_ns, in integer nanoseconds

all the values above are returned as an integer value of "0".

Here are the my flags in ubx_cfg.h:

#define UBLOX_PARSE_STATUS
#define UBLOX_PARSE_TIMEGPS
#define UBLOX_PARSE_TIMEUTC
#define UBLOX_PARSE_POSLLH
//#define UBLOX_PARSE_DOP
//#define UBLOX_PARSE_PVT
#define UBLOX_PARSE_VELNED
//#define UBLOX_PARSE_SVINFO
//#define UBLOX_PARSE_CFGNAV5
//#define UBLOX_PARSE_MONVER
//#define UBLOX_PARSE_HNR_PVT

Here are the flags in my NMEAGPS_cfg.h:

#define NMEAGPS_PARSE_GGA
//#define NMEAGPS_PARSE_GLL
//#define NMEAGPS_PARSE_GSA
#define NMEAGPS_PARSE_GSV
//#define NMEAGPS_PARSE_GST
#define NMEAGPS_PARSE_RMC
#define NMEAGPS_PARSE_VTG
//#define NMEAGPS_PARSE_ZDA
#define NMEAGPS_PARSE_SATELLITES
#define NMEAGPS_PARSE_SATELLITE_INFO
#define GPS_FIX_LOCATION_DMS

Does anyone know if there's a special message I have to enable on my ublox module (such as RXM, SEC, TIM, NAV or MON) or some combination of flags I have to enable to get the positional accuracy / error values I mentioned to have meaningful values?

What CODE are you using? Post that as well.

You will find the contents in each NMEA-sentence scroll to page 120+

What is the reason for needing the 'accuracy' values ?

My understanding is that these are statitical estimates only. So that if a GPS says its within say 5M, it really means there is a 50% chance that it is withing 5M, but it could be 10M or 30M out.