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AP_NMEA_Output.cpp: Fix conversion precision issue: 

We were casting the location in integer 32 bits
to float, and making fabsf in float as well, so
we were losing precision translated in about 40 cm
minimum variation in position for the NMEA output.

Also, even if using double and fabsF, we were still
rounding up last 2 decimals, so now the logic is
done in degree * 10e7 to not loose precision and
then converted properly before building the string
This commit is contained in:
davidsastresas 2022-09-23 13:29:36 +02:00 committed by Andrew Tridgell
parent ceb53ffa92
commit 243c32a3c4
1 changed files with 8 additions and 4 deletions
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12
libraries/AP_NMEA_Output/AP_NMEA_Output.cpp
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@ -16,6 +16,7 @@
Author: Francisco Ferreira (some code is copied from sitl_gps.cpp)
*/
#define ALLOW_DOUBLE_MATH_FUNCTIONS
#include "AP_NMEA_Output.h"
@ -101,22 +102,25 @@ void AP_NMEA_Output::update()
// format latitude
char lat_string[13];
float deg = fabsf(loc.lat * 1.0e-7f);
double deg = fabs(loc.lat * 1.0e-7f);
double min_dec = ((fabs(loc.lat) - (unsigned)deg * 1.0e7)) * 60 * 1.e-7f;
snprintf(lat_string,
sizeof(lat_string),
"%02u%08.5f,%c",
(unsigned) deg,
double((deg - int(deg)) * 60),
min_dec,
loc.lat < 0 ? 'S' : 'N');
// format longitude
char lng_string[14];
deg = fabsf(loc.lng * 1.0e-7f);
deg = fabs(loc.lng * 1.0e-7f);
min_dec = ((fabs(loc.lng) - (unsigned)deg * 1.0e7)) * 60 * 1.e-7f;
snprintf(lng_string,
sizeof(lng_string),
"%03u%08.5f,%c",
(unsigned) deg,
double((deg - int(deg)) * 60),
min_dec,
loc.lng < 0 ? 'W' : 'E');
// format GGA message