Re: [gpsd-dev] Bug in JSON encoding AIVDM type 9 messages

[Jon Schlueter]

Stefan Roels,

Can I get a couple of data samples for the following cases.

Type 8, DAC = 1 FID = 11: airtemp, dewpoint and watertemp calculations go wrong due to unsigned ints.

We seem to be missing any data samples that exercises this data path.

- Type 8, DAC = 1 FID = 16: This should only be decoded as "Persons on board" if the message length is either 72 or 136 bits long (if even then).
- Type 8, DAC = 1 FID = 16: If decoded, the json output should use the ais->type8.dac1fid16.persons field and not the type6 field

We seem to be missing any data samples that exercises the persons on board data flow It would be nice to make sure we don't regress backwards with other changes to the parser or storage logic.

- Type 9: the ais->type9.speed field should be used instead of the type1 field

We seem to be missing any data samples that exercise this test case where it fails.  I'm going to apply the patch but would like to make sure we have test cases covering this data flow if we don't already have any.

Thanks much

Jon

jschlueter on freenode #gpsd

On Mon, Oct 5, 2015 at 4:12 PM, Stefan Roels <address@hidden> wrote:

Dear all,

While working on my AIS decoder, I ran into some other bugs in the decoding and the JSON output.

- Type 8, DAC = 1 FID = 11: airtemp, dewpoint and watertemp calculations go wrong due to unsigned ints.
- Type 8, DAC = 1 FID = 16: This should only be decoded as "Persons on board" if the message length is either 72 or 136 bits long (if even then).
- Type 8, DAC = 1 FID = 16: If decoded, the json output should use the ais->type8.dac1fid16.persons field and not the type6 field
- Type 9: the ais->type9.speed field should be used instead of the type1 field

I have prepared a patch for these problems. I have also corrected some test outputs that are related to the spacing patch I send in earlier. Please do look at the test data, as I get some problems when running scons check, but I cannot find where I missed something.

Regards,
Stefan Roels



diff --git a/driver_ais.c b/driver_ais.c
index 1942ef7..abed4ca 100644
--- a/driver_ais.c
+++ b/driver_ais.c
@@ -527,11 +527,14 @@ bool ais_binary_decode(const struct gpsd_errout_t *errout,
                ais->type8.structured = true;
                break;
            case 16:        /* Number of Persons On Board */
-               if (ais->type8.bitcount == 136)
+               if (ais->type8.bitcount == 136) {
                    ais->type8.dac1fid16.persons = UBITS(88, 13);/* 289 */
-               else
+                       ais->type8.structured = true;
+               }
+               else if (ais->type8.bitcount == 72) {
                    ais->type8.dac1fid16.persons = UBITS(55, 13);/* 236 */
-               ais->type8.structured = true;
+                       ais->type8.structured = true;
+               }
                break;
            case 17:        /* IMO289 - VTS-generated/synthetic targets */
 #define ARRAY_BASE 56
diff --git a/gps.h b/gps.h
index 5602b0d..4954b8f 100644
--- a/gps.h
+++ b/gps.h
@@ -1314,13 +1314,13 @@ struct ais_t
 #define DAC1FID11_WDIR_NOT_AVAILABLE           511
                    unsigned int airtemp;       /* temperature, units 0.1C */
 #define DAC1FID11_AIRTEMP_NOT_AVAILABLE                2047
-#define DAC1FID11_AIRTEMP_OFFSET               600
+#define DAC1FID11_AIRTEMP_OFFSET               600.0
 #define DAC1FID11_AIRTEMP_DIV                  10.0
                    unsigned int humidity;      /* relative humidity, % */
 #define DAC1FID11_HUMIDITY_NOT_AVAILABLE       127
                    unsigned int dewpoint;      /* dew point, units 0.1C */
 #define DAC1FID11_DEWPOINT_NOT_AVAILABLE       1023
-#define DAC1FID11_DEWPOINT_OFFSET              200
+#define DAC1FID11_DEWPOINT_OFFSET              200.0
 #define DAC1FID11_DEWPOINT_DIV         10.0
                    unsigned int pressure;      /* air pressure, hpa */
 #define DAC1FID11_PRESSURE_NOT_AVAILABLE       511
@@ -1362,7 +1362,7 @@ struct ais_t
 #define DAC1FID11_SEASTATE_NOT_AVAILABLE       15
                    unsigned int watertemp;     /* units 0.1deg Celsius */
 #define DAC1FID11_WATERTEMP_NOT_AVAILABLE      1023
-#define DAC1FID11_WATERTEMP_OFFSET             100
+#define DAC1FID11_WATERTEMP_OFFSET             100.0
 #define DAC1FID11_WATERTEMP_DIV                10.0
                    unsigned int preciptype;    /* 0-7, enumerated */
 #define DAC1FID11_PRECIPTYPE_NOT_AVAILABLE     7
diff --git a/gpsd_json.c b/gpsd_json.c
index 6641846..839727f 100644
--- a/gpsd_json.c
+++ b/gpsd_json.c
@@ -2296,7 +2296,7 @@ void json_aivdm_dump(const struct ais_t *ais,
                break;
            case 16:    /* IMO289 - Number of persons on board */
                str_appendf(buf, buflen,
-                              "\"persons\":%u}\r\n", ais->type6.dac1fid16.persons);
+                              "\"persons\":%u}\r\n", ais->type8.dac1fid16.persons);
                break;
            case 17:        /* IMO289 - VTS-generated/synthetic targets */
                (void)strlcat(buf, "\"targets\":[", buflen);
@@ -2804,7 +2804,7 @@ void json_aivdm_dump(const struct ais_t *ais,
                (void)strlcpy(speedlegend, "\"fast\"", sizeof(speedlegend));
            else
                (void)snprintf(speedlegend, sizeof(speedlegend),
-                              "%u", ais->type1.speed);
+                              "%u", ais->type9.speed);

            str_appendf(buf, buflen,
"\"alt\":%s,\"speed\":%s,\"accuracy\":%s,"
diff --git a/test/sample.aivdm b/test/sample.aivdm
index cc413c3..8321f73 100644
--- a/test/sample.aivdm
+++ b/test/sample.aivdm
@@ -483,6 +483,25 @@
 #       RAIM flag                : 0
 #       Radio status             : 24597
 #
+# Type 9:
+# From AISHub
+!AIVDM,1,1,,B,91b55wi;address@hidden,0*30
+#       Message Type             : 9
+#       Repeat Indicator         : 0
+#       MMSI                     : 111232511
+#       Altitude                 : 303
+#       SOG                      : 42
+#       Position Accuracy        : 0
+#       Longitude                : 0xFC683F6 (-6.27884)
+#       Latitude                 : 0x2145300 ( 58.144 )
+#       Course Over Ground       : 0x0609 (154.5)
+#       Time Stamp               : 15
+#       Regional reserved        : 0
+#       DTE                      : 1
+#       Assigned                 : 0
+#       RAIM flag                : 0
+#       Radio status             : 33392
+#
 # Type 10:
 # From Kurt Schwehr. Two destination MMSIs. Checked with the noaadata tools.
 !AIVDM,1,1,,B,:5MlU41GMK6@,0*6C
diff --git a/test/sample.aivdm.js.chk b/test/sample.aivdm.js.chk
index ccfa428..8671140 100644
--- a/test/sample.aivdm.js.chk
+++ b/test/sample.aivdm.js.chk
@@ -21,10 +21,11 @@
 {"class":"AIS","device":"stdin","type":8,"repeat":0,"mmsi":244650946,"scaled":true,"dac":200,"fid":10,"vin":"02103547","length":390,"beam":50,"shiptype":8010,"shiptype_text":"Motor freighter","hazard":0,"hazard_text":"0 blue cones/lights","draught":204,"loaded":1,"loaded_text":"Unloaded","speed_q":false,"course_q":false,"heading_q":false}
 {"class":"AIS","device":"stdin","type":8,"repeat":0,"mmsi":244650946,"scaled":true,"dac":200,"fid":10,"data":"368:c32c70cf5d370c3064fa50198800b4987e9555557e083a544f082003b809ae511bfc75f0a7ff960808ccb6be7ed5"}
 {"class":"AIS","device":"stdin","type":9,"repeat":0,"mmsi":111265591,"scaled":true,"alt":15,"speed":0,"accuracy":false,"lon":11.8816,"lat":57.7785,"course":0.0,"second":28,"regional":0,"dte":0,"raim":false,"radio":49194}
+{"class":"AIS","device":"stdin","type":9,"repeat":0,"mmsi":111232511,"scaled":true,"alt":303,"speed":42,"accuracy":false,"lon":-6.2788,"lat":58.1440,"course":154.5,"second":15,"regional":0,"dte":1,"raim":false,"radio":33392}^M
 {"class":"AIS","device":"stdin","type":10,"repeat":0,"mmsi":366814480,"scaled":true,"dest_mmsi":366832740}
 {"class":"AIS","device":"stdin","type":10,"repeat":0,"mmsi":440882000,"scaled":true,"dest_mmsi":366972000}
 {"class":"AIS","device":"stdin","type":11,"repeat":0,"mmsi":304137000,"scaled":true,"timestamp":"2009-05-22T02:22:40Z","accuracy":true,"lon":-94.4077,"lat":28.4091,"epfd":1,"epfd_text":"GPS","raim":false,"radio":0}
-{"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":2275200,"scaled":true,"seqno":0,"dest_mmsi":215724000,"retransmit":false,"text":"PLEASE REPORT TO JOBOURG TRAFFIC CHANNEL 13 "}
+{"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":2275200,"scaled":true,"seqno":0,"dest_mmsi":215724000,"retransmit":false,"text":"PLEASE REPORT TO JOBOURG TRAFFIC CHANNEL 13"}^M
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":351853000,"scaled":true,"seqno":0,"dest_mmsi":316123456,"retransmit":false,"text":"GOOD"}
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":351853000,"scaled":true,"seqno":1,"dest_mmsi":351809000,"retransmit":false,"text":"THANX"}
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":271002099,"scaled":true,"seqno":0,"dest_mmsi":271002111,"retransmit":true,"text":"MSG FROM 271002099"}
diff --git a/test/sample.aivdm.ju.chk b/test/sample.aivdm.ju.chk
index a6de2b3..00e2dce 100644
--- a/test/sample.aivdm.ju.chk
+++ b/test/sample.aivdm.ju.chk
@@ -24,7 +24,7 @@
 {"class":"AIS","device":"stdin","type":10,"repeat":0,"mmsi":366814480,"scaled":false,"dest_mmsi":366832740}
 {"class":"AIS","device":"stdin","type":10,"repeat":0,"mmsi":440882000,"scaled":false,"dest_mmsi":366972000}
 {"class":"AIS","device":"stdin","type":11,"repeat":0,"mmsi":304137000,"scaled":false,"timestamp":"2009-05-22T02:22:40Z","accuracy":true,"lon":-56644610,"lat":17045470,"epfd":1,"epfd_text":"GPS","raim":false,"radio":0}
-{"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":2275200,"scaled":false,"seqno":0,"dest_mmsi":215724000,"retransmit":false,"text":"PLEASE REPORT TO JOBOURG TRAFFIC CHANNEL 13 "}
+{"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":2275200,"scaled":false,"seqno":0,"dest_mmsi":215724000,"retransmit":false,"text":"PLEASE REPORT TO JOBOURG TRAFFIC CHANNEL 13"}^M
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":351853000,"scaled":false,"seqno":0,"dest_mmsi":316123456,"retransmit":false,"text":"GOOD"}
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":351853000,"scaled":false,"seqno":1,"dest_mmsi":351809000,"retransmit":false,"text":"THANX"}
 {"class":"AIS","device":"stdin","type":12,"repeat":0,"mmsi":271002099,"scaled":false,"seqno":0,"dest_mmsi":271002111,"retransmit":true,"text":"MSG FROM 271002099"}