[AIS] Do scaling/offset operations only in json dump

splint and check pass.

8 files changed, 125 insertions, 118 deletions

diff --git a/driver_ais.c b/driver_ais.c
index 992063a3..385a448c 100644
--- a/driver_ais.c
+++ b/driver_ais.c
@@ -26,15 +26,6 @@
  * Parse the data from the device
  */
 
-#define DAC1FID11_AIRTEMP_OFFSET		600
-#define DAC1FID11_DEWPOINT_OFFSET		200
-#define DAC1FID11_PRESSURE_OFFSET		-800
-#define DAC1FID11_LEVEL_OFFSET			100
-#define DAC1FID11_WATERTEMP_OFFSET		100
-
-#define DAC1FID31_PRESSURE_OFFSET		-799
-#define DAC1FID31_LEVEL_OFFSET			1000
-
 static void from_sixbit(char *bitvec, uint start, int count, char *to)
 {
     /*@ +type @*/
@@ -408,17 +399,13 @@ bool ais_binary_decode(struct ais_t *ais,
 		ais->type8.dac1fid11.wgust		= UBITS(128, 7);
 		ais->type8.dac1fid11.wdir		= UBITS(135, 9);
 		ais->type8.dac1fid11.wgustdir	= UBITS(144, 9); 
-		ais->type8.dac1fid11.airtemp	= UBITS(153, 11)
-		    - DAC1FID11_AIRTEMP_OFFSET;
+		ais->type8.dac1fid11.airtemp	= UBITS(153, 11);
 		ais->type8.dac1fid11.humidity	= UBITS(164, 7);
-		ais->type8.dac1fid11.dewpoint	= UBITS(171, 10)
-		    - DAC1FID11_DEWPOINT_OFFSET;
-		ais->type8.dac1fid11.pressure	= UBITS(181, 9)
-		    - DAC1FID11_PRESSURE_OFFSET;
+		ais->type8.dac1fid11.dewpoint	= UBITS(171, 10);
+		ais->type8.dac1fid11.pressure	= UBITS(181, 9);
 		ais->type8.dac1fid11.pressuretend	= UBITS(190, 2);
 		ais->type8.dac1fid11.visibility	= UBITS(192, 8);
-		ais->type8.dac1fid11.waterlevel	= UBITS(200, 9)
-		    - DAC1FID11_LEVEL_OFFSET;
+		ais->type8.dac1fid11.waterlevel	= UBITS(200, 9);
 		ais->type8.dac1fid11.leveltrend	= UBITS(209, 2);
 		ais->type8.dac1fid11.cspeed		= UBITS(211, 8);
 		ais->type8.dac1fid11.cdir		= UBITS(219, 9);
@@ -435,8 +422,7 @@ bool ais_binary_decode(struct ais_t *ais,
 		ais->type8.dac1fid11.swellperiod	= UBITS(303, 6);
 		ais->type8.dac1fid11.swelldir	= UBITS(309, 9);
 		ais->type8.dac1fid11.seastate	= UBITS(318, 4);
-		ais->type8.dac1fid11.watertemp	= UBITS(322, 10)
-		    - DAC1FID11_WATERTEMP_OFFSET;
+		ais->type8.dac1fid11.watertemp	= UBITS(322, 10);
 		ais->type8.dac1fid11.preciptype	= UBITS(332, 3);
 		ais->type8.dac1fid11.salinity	= UBITS(335, 9);
 		ais->type8.dac1fid11.ice		= UBITS(344, 2);
@@ -554,13 +540,11 @@ bool ais_binary_decode(struct ais_t *ais,
 		ais->type8.dac1fid31.airtemp	= SBITS(154, 11);
 		ais->type8.dac1fid31.humidity	= UBITS(165, 7);
 		ais->type8.dac1fid31.dewpoint	= SBITS(172, 10);
-		ais->type8.dac1fid31.pressure	= UBITS(182, 9)
-		    - DAC1FID31_PRESSURE_OFFSET;
+		ais->type8.dac1fid31.pressure	= UBITS(182, 9);
 		ais->type8.dac1fid31.pressuretend	= UBITS(191, 2);
 		ais->type8.dac1fid31.visgreater	= UBITS(193, 1);
 		ais->type8.dac1fid31.visibility	= UBITS(194, 7);
-		ais->type8.dac1fid31.waterlevel	= UBITS(201, 12)
-		    - DAC1FID31_LEVEL_OFFSET;
+		ais->type8.dac1fid31.waterlevel	= UBITS(201, 12);
 		ais->type8.dac1fid31.leveltrend	= UBITS(213, 2);
 		ais->type8.dac1fid31.cspeed		= UBITS(215, 8);
 		ais->type8.dac1fid31.cdir		= UBITS(223, 9);
diff --git a/gps.h b/gps.h
index 09439ff3..966a2fee 100644
--- a/gps.h
+++ b/gps.h
@@ -1124,9 +1124,9 @@ struct ais_t
 		struct {
 #define DAC1FID11_LATLON_SCALE			1000
 		    int lon;			/* longitude in minutes * .001 */
-#define DAC1FID11_LON_NOT_AVAILABLE		0x1FFFFFF
-		    int lat;			/* longitude in minutes * .001 */
-#define DAC1FID11_LAT_NOT_AVAILABLE		0xFFFFFF
+#define DAC1FID11_LON_NOT_AVAILABLE		0xFFFFFF
+		    int lat;			/* latitude in minutes * .001 */
+#define DAC1FID11_LAT_NOT_AVAILABLE		0x7FFFFF
 		    unsigned int day;		/* UTC day */
 		    unsigned int hour;		/* UTC hour */
 		    unsigned int minute;	/* UTC minute */
@@ -1136,24 +1136,33 @@ struct ais_t
 		    unsigned int wdir;		/* wind direction */
 		    unsigned int wgustdir;	/* wind gust direction */
 #define DAC1FID11_WDIR_NOT_AVAILABLE		511
-		    int airtemp;		/* temperature, units 0.1C */
-#define DAC1FID11_AIRTEMP_NOT_AVAILABLE		1447
+		    unsigned int airtemp;		/* temperature, units 0.1C */
+#define DAC1FID11_AIRTEMP_NOT_AVAILABLE		2047
+#define DAC1FID11_AIRTEMP_OFFSET		600
+#define DAC1FID11_AIRTEMP_SCALE			10.0
 		    unsigned int humidity;	/* relative humidity, % */
 #define DAC1FID11_HUMIDITY_NOT_AVAILABLE	127
-		    int dewpoint;		/* dew point, units 0.1C */
-#define DAC1FID11_DEWPOINT_NOT_AVAILABLE	823
+		    unsigned int dewpoint;		/* dew point, units 0.1C */
+#define DAC1FID11_DEWPOINT_NOT_AVAILABLE	1023
+#define DAC1FID11_DEWPOINT_OFFSET		200
+#define DAC1FID11_DEWPOINT_SCALE		10.0
 		    unsigned int pressure;	/* air pressure, hpa */
-#define DAC1FID11_PRESSURE_NOT_AVAILABLE	1311
+#define DAC1FID11_PRESSURE_NOT_AVAILABLE	511
+#define DAC1FID11_PRESSURE_OFFSET		-800
 		    unsigned int pressuretend;	/* tendency */
 #define DAC1FID11_PRESSURETREND_NOT_AVAILABLE	3
 		    unsigned int visibility;	/* units 0.1 nautical miles */
 #define DAC1FID11_VISIBILITY_NOT_AVAILABLE	255
-		    int waterlevel;		/* decimeters */
-#define DAC1FID11_WATERLEVEL_NOT_AVAILABLE	411
+#define DAC1FID11_VISIBILITY_SCALE		10.0
+		    unsigned int waterlevel;		/* decimeters */
+#define DAC1FID11_WATERLEVEL_NOT_AVAILABLE	511
+#define DAC1FID11_WATERLEVEL_OFFSET		100
+#define DAC1FID11_WATERLEVEL_SCALE		10.0
 		    unsigned int leveltrend;	/* water level trend code */
-#define DAC1FID11_LEVELTREND_NOT_AVAILABLE	3
+#define DAC1FID11_WATERLEVELTREND_NOT_AVAILABLE	3
 		    unsigned int cspeed;	/* surface current speed in deciknots */
 #define DAC1FID11_CSPEED_NOT_AVAILABLE		255
+#define DAC1FID11_CSPEED_SCALE			10.0
 		    unsigned int cdir;		/* surface current dir., degrees */
 #define DAC1FID11_CDIR_NOT_AVAILABLE		511
 		    unsigned int cspeed2;	/* current speed in deciknots */
@@ -1165,6 +1174,7 @@ struct ais_t
 		    unsigned int cdepth3;	/* measurement depth, m */
 		    unsigned int waveheight;	/* in decimeters */
 #define DAC1FID11_WAVEHEIGHT_NOT_AVAILABLE	255
+#define DAC1FID11_WAVEHEIGHT_SCALE		10.0
 		    unsigned int waveperiod;	/* in seconds */
 #define DAC1FID11_WAVEPERIOD_NOT_AVAILABLE	63
 		    unsigned int wavedir;	/* direction in degrees */
@@ -1174,12 +1184,15 @@ struct ais_t
 		    unsigned int swelldir;	/* direction in degrees */
 		    unsigned int seastate;	/* Beaufort scale, 0-12 */
 #define DAC1FID11_SEASTATE_NOT_AVAILABLE	15
-		    int watertemp;		/* units 0.1deg Celsius */
-#define DAC1FID11_WATERTEMP_NOT_AVAILABLE	923
+		    unsigned int watertemp;		/* units 0.1deg Celsius */
+#define DAC1FID11_WATERTEMP_NOT_AVAILABLE	1023
+#define DAC1FID11_WATERTEMP_OFFSET		100
+#define DAC1FID11_WATERTEMP_SCALE		10.0
 		    unsigned int preciptype;	/* 0-7, enumerated */
 #define DAC1FID11_PRECIPTYPE_NOT_AVAILABLE	7
 		    unsigned int salinity;	/* units of 0.1ppt */
 #define DAC1FID11_SALINITY_NOT_AVAILABLE	511
+#define DAC1FID11_SALINITY_SCALE		10.0
 		    unsigned int ice;		/* is there sea ice? */
 #define DAC1FID11_ICE_NOT_AVAILABLE		3
 		} dac1fid11;
@@ -1270,34 +1283,43 @@ struct ais_t
 #define DAC1FID31_DIR_NOT_AVAILABLE		360
 		    int airtemp;		/* temperature, units 0.1C */
 #define DAC1FID31_AIRTEMP_NOT_AVAILABLE		-1024
+#define DAC1FID31_AIRTEMP_SCALE			10.0
 		    unsigned int humidity;	/* relative humidity, % */
 #define DAC1FID31_HUMIDITY_NOT_AVAILABLE	101
 		    int dewpoint;		/* dew point, units 0.1C */
 #define DAC1FID31_DEWPOINT_NOT_AVAILABLE	501
+#define DAC1FID31_DEWPOINT_SCALE		10.0
 		    unsigned int pressure;	/* air pressure, hpa */
 #define DAC1FID31_PRESSURE_NOT_AVAILABLE	511
 #define DAC1FID31_PRESSURE_HIGH			402
+#define DAC1FID31_PRESSURE_OFFSET		-799
 		    unsigned int pressuretend;	/* tendency */
 #define DAC1FID31_PRESSURETEND_NOT_AVAILABLE	3
 		    bool visgreater;            /* visibility greater than */
 		    unsigned int visibility;	/* units 0.1 nautical miles */
 #define DAC1FID31_VISIBILITY_NOT_AVAILABLE	127
-		    int waterlevel;		/* decimeters or cm */
+#define DAC1FID31_VISIBILITY_SCALE		10.0
+		    int waterlevel;		/* cm */
 #define DAC1FID31_WATERLEVEL_NOT_AVAILABLE	4001
+#define DAC1FID31_WATERLEVEL_OFFSET		1000
+#define DAC1FID31_WATERLEVEL_SCALE		100.0
 		    unsigned int leveltrend;	/* water level trend code */
-#define DAC1FID31_LEVELTREND_NOT_AVAILABLE	3
+#define DAC1FID31_WATERLEVELTREND_NOT_AVAILABLE	3
 		    unsigned int cspeed;	/* current speed in deciknots */
 #define DAC1FID31_CSPEED_NOT_AVAILABLE		255
+#define DAC1FID31_CSPEED_SCALE			10.0
 		    unsigned int cdir;		/* current dir., degrees */
 		    unsigned int cspeed2;	/* current speed in deciknots */
 		    unsigned int cdir2;		/* current dir., degrees */
 		    unsigned int cdepth2;	/* measurement depth, 0.1m */
 #define DAC1FID31_CDEPTH_NOT_AVAILABLE		301
+#define DAC1FID31_CDEPTH_SCALE			10.0
 		    unsigned int cspeed3;	/* current speed in deciknots */
 		    unsigned int cdir3;		/* current dir., degrees */
 		    unsigned int cdepth3;	/* measurement depth, 0.1m */
 		    unsigned int waveheight;	/* in decimeters */
 #define DAC1FID31_HEIGHT_NOT_AVAILABLE		31
+#define DAC1FID31_HEIGHT_SCALE			10.0
 		    unsigned int waveperiod;	/* in seconds */
 #define DAC1FID31_PERIOD_NOT_AVAILABLE		63
 		    unsigned int wavedir;	/* direction in degrees */
@@ -1308,10 +1330,12 @@ struct ais_t
 #define DAC1FID31_SEASTATE_NOT_AVAILABLE	15
 		    int watertemp;		/* units 0.1deg Celsius */
 #define DAC1FID31_WATERTEMP_NOT_AVAILABLE	601
+#define DAC1FID31_WATERTEMP_SCALE		10.0
 		    unsigned int preciptype;	/* 0-7, enumerated */
 #define DAC1FID31_PRECIPTYPE_NOT_AVAILABLE	7
-		    unsigned int salinity;	/* units of 0.1% */
+		    unsigned int salinity;	/* units of 0.1 permil (ca. PSU) */
 #define DAC1FID31_SALINITY_NOT_AVAILABLE	510
+#define DAC1FID31_SALINITY_SCALE		10.0
 		    unsigned int ice;		/* is there sea ice? */
 #define DAC1FID31_ICE_NOT_AVAILABLE		3
 		} dac1fid31;
diff --git a/gpsd_json.c b/gpsd_json.c
index cdbc13a2..c5a00849 100644
--- a/gpsd_json.c
+++ b/gpsd_json.c
@@ -2118,7 +2118,7 @@ void json_aivdm_dump(const struct ais_t *ais,
 	if (ais->type8.dac == 1) {
 	    const char *trends[] = {
 		"steady",
-		"increasing"
+		"increasing",
 		"decreasing",
 		"N/A",
 	    };
@@ -2169,13 +2169,13 @@ void json_aivdm_dump(const struct ais_t *ais,
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"airtemp\":%.1f,\"dewpoint\":%.1f,"
 				   "\"pressure\":%u,\"pressuretend\":\"%s\",",
-				   ais->type8.dac1fid11.airtemp * 0.1,
-				   ais->type8.dac1fid11.dewpoint * 0.1,
-				   ais->type8.dac1fid11.pressure,
+				   (ais->type8.dac1fid11.airtemp - DAC1FID11_AIRTEMP_OFFSET) / DAC1FID11_AIRTEMP_SCALE,
+				   (ais->type8.dac1fid11.dewpoint - DAC1FID11_DEWPOINT_OFFSET) / DAC1FID11_DEWPOINT_SCALE,
+				   ais->type8.dac1fid11.pressure - DAC1FID11_PRESSURE_OFFSET,
 				   trends[ais->type8.dac1fid11.pressuretend]);
 		else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
-				   "\"airtemp\":%d,\"dewpoint\":%d,"
+				   "\"airtemp\":%u,\"dewpoint\":%u,"
 				   "\"pressure\":%u,\"pressuretend\":%u,",
 				   ais->type8.dac1fid11.airtemp,
 				   ais->type8.dac1fid11.dewpoint,
@@ -2185,19 +2185,19 @@ void json_aivdm_dump(const struct ais_t *ais,
 		if (scaled)
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"visibility\":%.1f,",
-				   ais->type8.dac1fid11.visibility * 0.1);
+				   ais->type8.dac1fid11.visibility / DAC1FID11_VISIBILITY_SCALE);
 		else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"visibility\":%u,",
 				   ais->type8.dac1fid11.visibility);
 		if (!scaled)
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
-				   "\"waterlevel\":%d,",
+				   "\"waterlevel\":%u,",
 				   ais->type8.dac1fid11.waterlevel);
 		else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"waterlevel\":%.1f,",
-				   ais->type8.dac1fid11.waterlevel * 0.1);
+				   (ais->type8.dac1fid11.waterlevel - DAC1FID11_WATERLEVEL_OFFSET) / DAC1FID11_WATERLEVEL_SCALE);
 
 		if (scaled) {
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
@@ -2208,26 +2208,26 @@ void json_aivdm_dump(const struct ais_t *ais,
 				   "\"waveheight\":%.1f,\"waveperiod\":%u,\"wavedir\":%u,"
 				   "\"swellheight\":%.1f,\"swellperiod\":%u,\"swelldir\":%u,"
 				   "\"seastate\":%u,\"watertemp\":%.1f,"
-				   "\"preciptype\":%s,\"salinity\":%.1f,\"ice\":%s",
+				   "\"preciptype\":\"%s\",\"salinity\":%.1f,\"ice\":\"%s\"",
 				   trends[ais->type8.dac1fid11.leveltrend],
-				   ais->type8.dac1fid11.cspeed * 0.1,
+				   ais->type8.dac1fid11.cspeed / DAC1FID11_CSPEED_SCALE,
 				   ais->type8.dac1fid11.cdir,
-				   ais->type8.dac1fid11.cspeed2 * 0.1,
+				   ais->type8.dac1fid11.cspeed2 / DAC1FID11_CSPEED_SCALE,
 				   ais->type8.dac1fid11.cdir2,
 				   ais->type8.dac1fid11.cdepth2,
-				   ais->type8.dac1fid11.cspeed3 * 0.1,
+				   ais->type8.dac1fid11.cspeed3 / DAC1FID11_CSPEED_SCALE,
 				   ais->type8.dac1fid11.cdir3,
 				   ais->type8.dac1fid11.cdepth3,
-				   ais->type8.dac1fid11.waveheight * 0.1,
+				   ais->type8.dac1fid11.waveheight / DAC1FID11_WAVEHEIGHT_SCALE,
 				   ais->type8.dac1fid11.waveperiod,
 				   ais->type8.dac1fid11.wavedir,
-				   ais->type8.dac1fid11.swellheight * 0.1,
+				   ais->type8.dac1fid11.swellheight / DAC1FID11_WAVEHEIGHT_SCALE,
 				   ais->type8.dac1fid11.swellperiod,
 				   ais->type8.dac1fid11.swelldir,
 				   ais->type8.dac1fid11.seastate,
-				   ais->type8.dac1fid11.watertemp * 0.1,
+				   (ais->type8.dac1fid11.watertemp - DAC1FID11_WATERTEMP_OFFSET) / DAC1FID11_WATERTEMP_SCALE,
 				   preciptypes[ais->type8.dac1fid11.preciptype],
-				   ais->type8.dac1fid11.salinity * 0.1,
+				   ais->type8.dac1fid11.salinity / DAC1FID11_SALINITY_SCALE,
 				   ice[ais->type8.dac1fid11.ice]);
 		} else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
@@ -2237,7 +2237,7 @@ void json_aivdm_dump(const struct ais_t *ais,
 				   "\"cspeed3\":%u,\"cdir3\":%u,\"cdepth3\":%u,"
 				   "\"waveheight\":%u,\"waveperiod\":%u,\"wavedir\":%u,"
 				   "\"swellheight\":%u,\"swellperiod\":%u,\"swelldir\":%u,"
-				   "\"seastate\":%u,\"watertemp\":%d,"
+				   "\"seastate\":%u,\"watertemp\":%u,"
 				   "\"preciptype\":%u,\"salinity\":%u,\"ice\":%u",
 				   ais->type8.dac1fid11.leveltrend,
 				   ais->type8.dac1fid11.cspeed,
@@ -2451,12 +2451,12 @@ void json_aivdm_dump(const struct ais_t *ais,
 			       ais->type8.dac1fid31.humidity);
 		if (scaled)
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
-				   "\"airtemp\":%1f,\"dewpoint\":%1f,"
+				   "\"airtemp\":%.1f,\"dewpoint\":%.1f,"
 				   "\"pressure\":%u,\"pressuretend\":\"%s\","
 				   "\"visgreater\":%s,",
-				   ais->type8.dac1fid31.airtemp * 0.1,
-				   ais->type8.dac1fid31.dewpoint * 0.1,
-				   ais->type8.dac1fid31.pressure,
+				   ais->type8.dac1fid31.airtemp / DAC1FID31_AIRTEMP_SCALE,
+				   ais->type8.dac1fid31.dewpoint / DAC1FID31_DEWPOINT_SCALE,
+				   ais->type8.dac1fid31.pressure - DAC1FID31_PRESSURE_OFFSET,
 				   trends[ais->type8.dac1fid31.pressuretend],
 				   JSON_BOOL(ais->type8.dac1fid31.visgreater));
 		else
@@ -2473,7 +2473,7 @@ void json_aivdm_dump(const struct ais_t *ais,
 		if (scaled)
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"visibility\":%.1f,",
-				   ais->type8.dac1fid31.visibility * 0.1);
+				   ais->type8.dac1fid31.visibility / DAC1FID31_VISIBILITY_SCALE);
 		else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"visibility\":%u,",
@@ -2485,7 +2485,7 @@ void json_aivdm_dump(const struct ais_t *ais,
 		else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
 				   "\"waterlevel\":%.1f,",
-				   ais->type8.dac1fid31.waterlevel * 0.01);
+				   (ais->type8.dac1fid31.waterlevel - DAC1FID31_WATERLEVEL_OFFSET) / DAC1FID31_WATERLEVEL_SCALE);
 
 		if (scaled) {
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
@@ -2498,24 +2498,24 @@ void json_aivdm_dump(const struct ais_t *ais,
 				   "\"seastate\":%u,\"watertemp\":%.1f,"
 				   "\"preciptype\":\"%s\",\"salinity\":%.1f,\"ice\":\"%s\"",
 				   trends[ais->type8.dac1fid31.leveltrend],
-				   ais->type8.dac1fid31.cspeed * 0.1,
+				   ais->type8.dac1fid31.cspeed / DAC1FID31_CSPEED_SCALE,
 				   ais->type8.dac1fid31.cdir,
-				   ais->type8.dac1fid31.cspeed2 * 0.1,
+				   ais->type8.dac1fid31.cspeed2 / DAC1FID31_CSPEED_SCALE,
 				   ais->type8.dac1fid31.cdir2,
 				   ais->type8.dac1fid31.cdepth2,
-				   ais->type8.dac1fid31.cspeed3 * 0.1,
+				   ais->type8.dac1fid31.cspeed3 / DAC1FID31_CSPEED_SCALE,
 				   ais->type8.dac1fid31.cdir3,
 				   ais->type8.dac1fid31.cdepth3,
-				   ais->type8.dac1fid31.waveheight * 0.1,
+				   ais->type8.dac1fid31.waveheight / DAC1FID31_HEIGHT_SCALE,
 				   ais->type8.dac1fid31.waveperiod,
 				   ais->type8.dac1fid31.wavedir,
-				   ais->type8.dac1fid31.swellheight * 0.1,
+				   ais->type8.dac1fid31.swellheight / DAC1FID31_HEIGHT_SCALE,
 				   ais->type8.dac1fid31.swellperiod,
 				   ais->type8.dac1fid31.swelldir,
 				   ais->type8.dac1fid31.seastate,
-				   ais->type8.dac1fid31.watertemp * 0.1,
+				   ais->type8.dac1fid31.watertemp / DAC1FID31_WATERTEMP_SCALE,
 				   preciptypes[ais->type8.dac1fid31.preciptype],
-				   ais->type8.dac1fid31.salinity * 0.1,
+				   ais->type8.dac1fid31.salinity / DAC1FID31_SALINITY_SCALE,
 				   ice[ais->type8.dac1fid31.ice]);
 		} else
 		    (void)snprintf(buf + strlen(buf), buflen - strlen(buf),
diff --git a/gpsdecode.c b/gpsdecode.c
index 0198a66c..3ade9b8c 100644
--- a/gpsdecode.c
+++ b/gpsdecode.c
@@ -155,7 +155,7 @@ static void aivdm_csv_dump(struct ais_t *ais, char *buf, size_t buflen)
 	    switch(ais->type8.fid) {
 	    case 11:		/* IMO236 - Met/Hydro message */
 		(void)snprintf(buf + strlen(buf), buflen - strlen(buf),
-			       "|%d|%d|%02uT%02u:%02uZ|%u|%u|%u|%u|%d|%u|%d|%u|%u|%u|%d|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%d|%u|%u|%u",
+			       "|%d|%d|%02uT%02u:%02uZ|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u|%u",
 			       ais->type8.dac1fid11.lon,
 			       ais->type8.dac1fid11.lat,
 			       ais->type8.dac1fid11.day,
diff --git a/jsongen.py.in b/jsongen.py.in
index 7c85b3c5..cf785291 100644
--- a/jsongen.py.in
+++ b/jsongen.py.in
@@ -305,14 +305,14 @@ ais_specs = (
         ('wgust',        'uinteger',  'DAC1FID11_WSPEED_NOT_AVAILABLE'),
         ('wdir',         'uinteger',  'DAC1FID11_WDIR_NOT_AVAILABLE'),
         ('wgustdir',     'uinteger',  'DAC1FID11_WDIR_NOT_AVAILABLE'),
-        ('airtemp',      'integer',   'DAC1FID11_AIRTEMP_NOT_AVAILABLE'),
+        ('airtemp',      'uinteger',  'DAC1FID11_AIRTEMP_NOT_AVAILABLE'),
         ('humidity',     'uinteger',  'DAC1FID11_HUMIDITY_NOT_AVAILABLE'),
-        ('dewpoint',     'integer',   'DAC1FID11_DEWPOINT_NOT_AVAILABLE'),
+        ('dewpoint',     'uinteger',  'DAC1FID11_DEWPOINT_NOT_AVAILABLE'),
         ('pressure',     'uinteger',  'DAC1FID11_PRESSURE_NOT_AVAILABLE'),
         ('pressuretend', 'uinteger',  'DAC1FID11_PRESSURETREND_NOT_AVAILABLE'),
         ('visibility',   'uinteger',  'DAC1FID11_VISIBILITY_NOT_AVAILABLE'),
-        ('waterlevel',   'integer',   'DAC1FID11_WATERLEVEL_NOT_AVAILABLE'),
-        ('leveltrend',   'uinteger',  'DAC1FID11_LEVELTREND_NOT_AVAILABLE'),
+        ('waterlevel',   'uinteger',  'DAC1FID11_WATERLEVEL_NOT_AVAILABLE'),
+        ('leveltrend',   'uinteger',  'DAC1FID11_WATERLEVELTREND_NOT_AVAILABLE'),
         ('cspeed',       'uinteger',  'DAC1FID11_CSPEED_NOT_AVAILABLE'),
         ('cdir',         'uinteger',  'DAC1FID11_CDIR_NOT_AVAILABLE'),
         ('cspeed2',      'uinteger',  'DAC1FID11_CSPEED_NOT_AVAILABLE'),
@@ -328,7 +328,7 @@ ais_specs = (
         ('swellperiod',  'uinteger',  'DAC1FID11_WAVEPERIOD_NOT_AVAILABLE'),
         ('swelldir',     'uinteger',  'DAC1FID11_WAVEDIR_NOT_AVAILABLE'),
         ('seastate',     'uinteger',  'DAC1FID11_SEASTATE_NOT_AVAILABLE'),
-        ('watertemp',    'integer',   'DAC1FID11_WATERTEMP_NOT_AVAILABLE'),
+        ('watertemp',    'uinteger',  'DAC1FID11_WATERTEMP_NOT_AVAILABLE'),
         ('preciptype',   'uinteger',  'DAC1FID11_PRECIPTYPE_NOT_AVAILABLE'),
         ('salinity',     'uinteger',  'DAC1FID11_SALINITY_NOT_AVAILABLE'),
         ('ice',          'uinteger',  'DAC1FID11_ICE_NOT_AVAILABLE'),
@@ -455,7 +455,7 @@ ais_specs = (
         ('visgreater', 'boolean',  'false'),
         ('visibility', 'uinteger', 'DAC1FID31_VISIBILITY_NOT_AVAILABLE'),
         ('waterlevel', 'uinteger', 'DAC1FID31_WATERLEVEL_NOT_AVAILABLE'),
-        ('leveltrend', 'uinteger', 'DAC1FID31_LEVELTREND_NOT_AVAILABLE'),
+        ('leveltrend', 'uinteger', 'DAC1FID31_WATERLEVELTREND_NOT_AVAILABLE'),
         ('cspeed',     'uinteger', 'DAC1FID31_CSPEED_NOT_AVAILABLE'),
         ('cdir',       'uinteger', 'DAC1FID31_DIR_NOT_AVAILABLE'),
         ('cspeed2',    'uinteger', 'DAC1FID31_CSPEED_NOT_AVAILABLE'),
diff --git a/test/sample.aivdm.chk b/test/sample.aivdm.chk
index 6b6adfd8..3b698060 100644
--- a/test/sample.aivdm.chk
+++ b/test/sample.aivdm.chk
@@ -12,9 +12,9 @@
 7|2|537411077|43101326|717096664|76161024|0

 8|0|366999712|366|56|256:3a53dbb7be4a773137f87d7b0445f040dea05d93f593783194ae9b9d9dbe05fb

 8|0|999999999|366|56|256:eb0d4f917a035b2dfca3d4739381735c18ebbe754936f66850037dcacd9538b8

-8|0|992509977|1|11|-368039|3197693|18T17:15Z|3|6|12|15|142|50|123|1024|2|153|-84|1|103|256|104|257|10|126|203|20|42|35|25|23|48|124|3|123|6|53|0

-8|0|992509977|1|11|-368037|3197689|18T17:45Z|127|127|511|511|1447|127|823|1311|3|255|411|3|255|511|255|511|31|255|511|31|255|63|511|255|63|511|15|923|7|511|3

-8|0|992509977|1|31|-368044|3197696|29T23:24Z|127|127|360|360|-1024|101|501|1310|3|127|3001|3|255|360|255|360|31|255|360|31|255|63|360|255|63|360|13|501|7|510|3

+8|0|992509977|1|11|-368039|3197693|18T17:15Z|3|6|12|15|742|50|323|224|2|153|16|1|103|256|104|257|10|126|203|20|42|35|25|23|48|124|3|223|6|53|0

+8|0|992509977|1|11|-368037|3197689|18T17:45Z|127|127|511|511|2047|127|1023|511|3|255|511|3|255|511|255|511|31|255|511|31|255|63|511|255|63|511|15|1023|7|511|3

+8|0|992509977|1|31|-368044|3197696|29T23:24Z|127|127|360|360|-1024|101|501|511|3|127|4001|3|255|360|255|360|31|255|360|31|255|63|360|255|63|360|13|501|7|510|3

 9|0|111265591|15|0|0|7128960|34667073|0|28|0x0|0|0|0x6015

 10|0|366814480|366832740

 10|0|440882000|366972000

diff --git a/test/synthetic-ais.json b/test/synthetic-ais.json
index 3622a2a6..32edcd29 100644
--- a/test/synthetic-ais.json
+++ b/test/synthetic-ais.json
@@ -19,8 +19,8 @@
 {"class":"AIS","type":7,"repeat":2,"mmsi":537411077,"scaled":false,"mmsi1":43101326,"mmsi2":717096664,"mmsi3":76161024,"mmsi4":0}

 {"class":"AIS","type":8,"repeat":0,"mmsi":366999712,"scaled":false,"dac":366,"fid":22,"data":"256:3a53dbb7be4a773137f87d7b0445f040dea05d93f593783194ae9b9d9dbe05fb"}

 {"class":"AIS","type":8,"repeat":0,"mmsi":366999655,"scaled":false,"dac":366,"fid":22,"data":"256:631d1d6b32f735f03494870d9e13addaf3f373435347ab94628f1498868051c3"}

-{"class":"AIS","type":8,"repeat":0,"mmsi":992509977,"scaled":false,"dac":1,"fid":11,"lat":3197693,"lon":-368039,"timestamp":"18T17:15Z","wspeed":3,"wgust":6,"wdir":12,"wgustdir":15,"humidity":50,"airtemp":142,"dewpoint":123,"pressure":1024,"pressuretend":2,"visibility":153,"waterlevel":-84,"leveltrend":1,"cspeed":103,"cdir":256,"cspeed2":104,"cdir2":257,"cdepth2":10,"cspeed3":126,"cdir3":203,"cdepth3":20,"waveheight":42,"waveperiod":35,"wavedir":25,"swellheight":23,"swellperiod":48,"swelldir":124,"seastate":3,"watertemp":123,"preciptype":6,"salinity":53,"ice":0}
-{"class":"AIS","type":8,"repeat":0,"mmsi":992509977,"scaled":false,"dac":1,"fid":11,"lat":3197689,"lon":-368037,"timestamp":"18T17:45Z","wspeed":127,"wgust":127,"wdir":511,"wgustdir":511,"humidity":127,"airtemp":1447,"dewpoint":823,"pressure":1311,"pressuretend":3,"visibility":255,"waterlevel":411,"leveltrend":3,"cspeed":255,"cdir":511,"cspeed2":255,"cdir2":511,"cdepth2":31,"cspeed3":255,"cdir3":511,"cdepth3":31,"waveheight":255,"waveperiod":63,"wavedir":511,"swellheight":255,"swellperiod":63,"swelldir":511,"seastate":15,"watertemp":923,"preciptype":7,"salinity":511,"ice":3}
+{"class":"AIS","device":"stdin","type":8,"repeat":0,"mmsi":992509977,"scaled":false,"dac":1,"fid":11,"lat":3197689,"lon":-368037,"timestamp":"18T17:45Z","wspeed":127,"wgust":127,"wdir":511,"wgustdir":511,"humidity":127,"airtemp":2047,"dewpoint":1023,"pressure":511,"pressuretend":3,"visibility":255,"waterlevel":511,"leveltrend":3,"cspeed":255,"cdir":511,"cspeed2":255,"cdir2":511,"cdepth2":31,"cspeed3":255,"cdir3":511,"cdepth3":31,"waveheight":255,"waveperiod":63,"wavedir":511,"swellheight":255,"swellperiod":63,"swelldir":511,"seastate":15,"watertemp":1023,"preciptype":7,"salinity":511,"ice":3}
+{"class":"AIS","device":"stdin","type":8,"repeat":0,"mmsi":992509977,"scaled":false,"dac":1,"fid":31,"lat":3197696,"lon":-368044,"accuracy":false,"timestamp":"29T23:24Z","wspeed":127,"wgust":127,"wdir":360,"wgustdir":360,"humidity":101,"airtemp":-1024,"dewpoint":501,"pressure":511,"pressuretend":3,"visgreater":false,"visibility":127,"waterlevel":4001,"leveltrend":3,"cspeed":255,"cdir":360,"cspeed2":255,"cdir2":360,"cdepth2":31,"cspeed3":255,"cdir3":360,"cdepth3":31,"waveheight":255,"waveperiod":63,"wavedir":360,"swellheight":255,"swellperiod":63,"swelldir":360,"seastate":13,"watertemp":501,"preciptype":7,"salinity":510,"ice":3}
 {"class":"AIS","device":"stdin","type":8,"repeat":0,"mmsi":992509977,"scaled":false,"dac":1,"fid":31,"lat":3197696,"lon":-368044,"accuracy":false,"timestamp":"29T23:24Z","wspeed":127,"wgust":127,"wdir":360,"wgustdir":360,"humidity":101,"airtemp":-1024,"dewpoint":501,"pressure":1311,"pressuretend":3,"visgreater":false,"visibility":127,"waterlevel":3001,"leveltrend":3,"cspeed":255,"cdir":360,"cspeed2":255,"cdir2":360,"cdepth2":31,"cspeed3":255,"cdir3":360,"cdepth3":31,"waveheight":255,"waveperiod":63,"wavedir":360,"swellheight":255,"swellperiod":63,"swelldir":360,"seastate":13,"watertemp":501,"preciptype":7,"salinity":510,"ice":3}

 {"class":"AIS","type":9,"repeat":0,"mmsi":111265591,"scaled":false,"alt":15,"speed":0,"accuracy":false,"lon":7128960,"lat":34667073,"course":0,"second":28,"regional":0,"dte":0,"raim":false,"radio":24597}

 {"class":"AIS","type":10,"repeat":0,"mmsi":366814480,"scaled":false,"dest_mmsi":366832740}

diff --git a/www/AIVDM.txt b/www/AIVDM.txt
index a58b7322..9bf9b54b 100644
--- a/www/AIVDM.txt
+++ b/www/AIVDM.txt
@@ -1871,100 +1871,99 @@ broadcast of this message of 12 minutes.
 |40-49   | 10 |DAC                |dac         |u|DAC = 001
 |50-55   |  6 |FID                |fid         |u|FID = 11
 |56-79   | 24 |Latitude           |lat         |I3|Unit = minutes * 0.001,
-                                                  91000 = N/A (default),
+                                                  0x7FFFFF = N/A (default),
                                                   E positive, W negative.
 |80-104  | 25 |Longitude          |lon         |I3|Unit = minutes * 0.001,
-                                                  181000 = N/A (default),
+                                                  0xFFFFFF = N/A (default),
                                                   N positive, S negative.
-|105-109 |  5 |Day (UTC)          |day         |u|1-31, 0=N/A (default)
-|110-114 |  5 |Hour (UTC)         |hour        |u|0-23, >=24=N/A (default)
-|115-120 |  6 |Minute (UTC)       |minute      |u|0-59, >=60=N/A (default)
+|105-109 |  5 |Day (UTC)          |day         |u|1-31, 31=N/A (default)
+|110-114 |  5 |Hour (UTC)         |hour        |u|0-23, 31=N/A (default)
+|115-120 |  6 |Minute (UTC)       |minute      |u|0-59, 63=N/A (default)
 |121-127 |  7 |Average Wind Speed |wspeed      |u|10-min avg wind speed, knots,
                                                   127 = N/A (default).
 |128-134 |  7 |Gust Speed         |wgust       |u|10-min max wind speed, knots,
                                                   127 = N/A (default).
 |135-143 |  9 |Wind Direction     |wdir        |u|0-359, degrees fom true north
-                                                   >=360 = N/A (default)
+                                                   511 = N/A (default)
 |144-152 |  9 |Wind Gust Direction|wgustdir    |u|0-359, degrees fom true north
-                                                   >=360 = N/A (default)
+                                                   511 = N/A (default)
 |153-163 | 11 |Air Temperature    |temperature |u|Dry bulb temp: 0.1 deg C
                                                   -60.0 to +60.0,
-                                                  -1024 = N/A (default),
-                                                  else -60deg after scaling.
+                                                  2047 = N/A (default),
 |164-170 |  7 |Relative Humidity  |humidity    |u|0-100%, units of 1%,
                                                   127 = N/A (default).
 |171-180 | 10 |Dew Point          |dewpoint    |u|-20.0 to +50.0: 0.1 deg C,
                                                   1023 = N/A (default),
-                                                  else -20.0deg after scaling.
 |181-189 |  9 |Air Pressure       |pressure    |u|800-1200hPa: units 1hPa,
-                                                  402 = pressure >= 1201 hPa,
-                                                  403 - N/A (default).
-                                                  else add 400 to value.
+                                                  511 = N/A (default).
 |190-191 |  2 |Pressure Tendency  |pressuretend|e|0 = steady,
                                                   1 = decreasing,
                                                   2 = increasing,
                                                   3 - N/A (default).
 |192-199 |  8 |Horiz. Visibility  |visibility  |U1|0-25.0, units of 0.1nm
-                                                  >= 250 = N/A (default)
+                                                  255 = N/A (default)
 |200-208 |  9 |Water Level        |waterlevel  |U1|-10.0 to +30.0 in 0.1m,
-                                                  1923 = N/A (default).
-                                                  else -10m after scaling.
+                                                  511 = N/A (default).
 |209-210 |  2 |Water Level Trend  |leveltrend  |e|0 = steady,
                                                   1 = decreasing,
                                                   2 = increasing,
                                                   3 - N/A (default).
 |211-218 |  8 |Surface Current Speed     |cspeed  |U1|0.0-25.0 knots: units 0.1 knot
 |219-227 |  9 |Surface Current Direction |cdir    |u|0-359: deg from true north,
-                                                     >=360 = N/A (default)
+                                                     511 = N/A (default)
 |228-235 |  8 |Current Speed #2     |cspeed2   |U1|0.0-25.0 in units of 0.1 knot,
-                                                  >=251 = N/A (default).
+                                                  255 = N/A (default).
 |236-244 |  9 |Current Direction #2 |cdir2     |u|0-359: deg. fom true north,
-                                                  >=360 = N/A (default)
+                                                  511 = N/A (default)
 |245-249 |  5 |Measurement Depth #2 |cdepth2   |U1|0-30m down: units 0.1m,
                                                    31 = N/A (default).
 |250-257 |  8 |Current Speed #3     |cspeed3   |U1|0.0-25.0: units of 0.1 knot,
-                                                   >=251 = N/A (default).
+                                                   255 = N/A (default).
 |258-266 |  9 |Current Direction #3 |cdir3     |u|0-359: degrees fom true north,
-                                                  >=360 = N/A (default).
+                                                  511 = N/A (default).
 |267-271 |  5 |Measurement Depth #3 |cdepth3   |U1|0-30m down: units 0.1m,
                                                   31 = N/A (default).
 |272-279 |  8 |Wave height          |waveheight|U1|0-25m: units of 0.1m,
-                                                  >=251 = N/A (default).
+                                                  255 = N/A (default).
 |280-285 |  6 |Wave period          |waveperiod|u|Seconds 0-60:
-                                                  >= 61 = N/A (default).
+                                                  63 = N/A (default).
 |286-294 |  9 |Wave direction       |wavedir   |u|0-359: deg. fom true north,
-                                                  >=360 = N/A (default).
+                                                  511 = N/A (default).
 |295-302 |  8 |Swell height         |swellheight|U1|0-25m: units of 0.1m
-                                                   >=251 = N/A (default).
+                                                   255 = N/A (default).
 |303-308 |  6 |Swell period         |swellperiod|u|Seconds 0-60:
-                                                   >= 61 = N/A (default).
+                                                   63 = N/A (default).
 |309-317 |  9 |Swell direction      |swelldir   |u|0-359: deg. fom true north,
-                                                   >=360 = N/A (default).
+                                                   511 = N/A (default).
 |318-321 |  4 |Sea state            |seastate   |e|See "Beaufort Scale"
 |322-331 | 10 |Water Temperature    |watertemp  |U1|-10.0 to 50.0: units 0.1 C,
-                                                   >=601 = N/A (default).
-                                                   else -10.0m after scaling.
+                                                   1023 = N/A (default).
 |332-334 |  3 |Precipitation        |preciptype |e|See "Precipitation Types"
 |335-343 |  9 |Salinity             |salinity   |U1|0.0-50.0%: units 0.1%,
-                                                   >=500 = N/A (default)
-|344-345 |  2 |Ice                  |ice        |b|Yes/No
+                                                   511 = N/A (default)
+|344-345 |  2 |Ice                  |ice        |e| 0 = No
+                                                    1 = Yes
+                                                    2 = (reserved for future use)
+                                                    3 = not available = default
 |346-351 |  6 |Spare                |           |x|Not used
 |==============================================================================
 
 <<IMO236>> says "If there is no data available, default value to be
 transmitted is the highest available binary value for that particular
-data field." and no defaults are explicitly specified. However, the
-replacement FID=31 message has default values which do not obey this
-rule. It would be good practice for a decoder to treat any
-out-of-bounds value as N/A; the N/A formulas in the table above
-reflect this.
+data field.", the above table reflects that. 
+The day, hour and minute have to be considered not available when all 
+three are set to their individual "N/A" value.
+For the latitude and the longitude, the highest positive value is used, 
+as the highest available binary value for a signed integer is -1, which 
+would forbid the -0.001/-0.001 position. 
+The replacement FID=31 message has different default values that remove any ambiguities.
 
 <<IMO236>> gives the length of this message as 352, but lists only 336 
 payload bits.
 
 Water level is deviation from local chart datum and includes tide.
 
-The waveheight field is labeled as "Significant" in <<IMO238>>, 
+The waveheight field is labeled as "Significant" in <<IMO236>>, 
 for whatever that means.
 
 The seastate field has a note in <<IMO236>> reading "(manual input?)"?