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| author | Eric S. Raymond <esr@thyrsus.com> | 2009-09-30 22:03:11 +0000 |
|---|---|---|
| committer | Eric S. Raymond <esr@thyrsus.com> | 2009-09-30 22:03:11 +0000 |
| commit | 97b9548cff261e13a5b592d31add94631ff4dbc9 (patch) | |
| tree | f46a1c984d841d3d2d8d83836d01db57d3e8ccf9 /driver_navcom.c | |
| parent | b9f18fea09961f5e7476130a67e4e89379e12571 (diff) | |
| download | gpsd-97b9548cff261e13a5b592d31add94631ff4dbc9.tar.gz | |
Fix computation of epx and epy from eph.
Factor of 1/sqrt(2) has to be applied (on the assumption that epx and
epy are equal).
Diffstat (limited to 'driver_navcom.c')
| -rw-r--r-- | driver_navcom.c | 23 |
1 files changed, 9 insertions, 14 deletions
diff --git a/driver_navcom.c b/driver_navcom.c index 8beef935..826fb12e 100644 --- a/driver_navcom.c +++ b/driver_navcom.c @@ -391,6 +391,7 @@ static gps_mask_t handle_0xb1(struct gps_device_t *session) #define VEL_RES (0.0009765625) double track; uint8_t fom, gdop, pdop, hdop, vdop, tdop, tfom; + double eph; /* This value means "undefined" */ #define DOP_UNDEFINED (255) @@ -480,19 +481,13 @@ static gps_mask_t handle_0xb1(struct gps_device_t *session) vdop = getub(buf, 44); tdop = getub(buf, 45); tfom = getub(buf, 46); - /*@ +type @*/ - /* splint apparently gets confused about C promotion rules. */ - /* "Assignment of arbitrary unsigned integral type to double" on these */ -#ifndef S_SPLINT_S - session->gpsdata.fix.epx = session->gpsdata.fix.epy = fom/100.0*1.96/*Two sigma*/; - /* FIXME - Which units is tfom in (spec doesn't say) and - which units does gpsd require? (docs don't say) */ - session->gpsdata.fix.ept = tfom*1.96/*Two sigma*/; - /* FIXME This cannot possibly be right */ - /* I cannot find where to get VRMS from in the Navcom output, though, - and this value seems to agree with the output from other software */ - session->gpsdata.fix.epv = (double)fom/(double)hdop*(double)vdop/100.0*1.96/*Two sigma*/; + /* Get two-sigma horizontal circular error estimate */ + eph = fom/100.0 * 1.96; + /* approximate epx and epy errors from it */ + session->gpsdata.fix.epx = session->gpsdata.fix.epy = eph/sqrt(2); + /* FIXME - Which units is tfom in (spec doesn't say) */ + session->gpsdata.fix.ept = tfom * 1.96 /*Two sigma*/; clear_dop(&session->gpsdata.dop); if (gdop != DOP_UNDEFINED) @@ -505,7 +500,7 @@ static gps_mask_t handle_0xb1(struct gps_device_t *session) session->gpsdata.dop.vdop = vdop/10.0; if (tdop != DOP_UNDEFINED) session->gpsdata.dop.tdop = tdop/10.0; -#endif /* S_SPLINT_S */ + /*@ +type @*/ gpsd_report(LOG_PROG, "Navcom: received packet type 0xb1 (PVT Report)\n"); gpsd_report(LOG_IO, "Navcom: navigation mode %s (0x%02x) - %s - %s\n", @@ -518,7 +513,7 @@ static gps_mask_t handle_0xb1(struct gps_device_t *session) "Navcom: velocities: north = %f, east = %f, up = %f (track = %f, speed = %f)\n", vel_north*VEL_RES, vel_east*VEL_RES, vel_up*VEL_RES, session->gpsdata.fix.track, session->gpsdata.fix.speed); - /* relies on the fact that expcx and epy are set to same value */ + /* relies on the fact that expx and epy are set to same value */ gpsd_report(LOG_IO, "Navcom: hrms = %f, vrms = %f, gdop = %f, pdop = %f, " "hdop = %f, vdop = %f, tdop = %f\n", |