[hamradio-commits] [dump1090] 22/389: CPR position decoding. Track calculation from velocity components.
Matthew Ernisse
mernisse-guest at moszumanska.debian.org
Wed Nov 5 00:19:36 UTC 2014
This is an automated email from the git hooks/post-receive script.
mernisse-guest pushed a commit to branch master
in repository dump1090.
commit b6907f400aa37dbad33904bdda709ff094a8f3de
Author: antirez <antirez at gmail.com>
Date: Wed Jan 9 22:51:29 2013 +0100
CPR position decoding. Track calculation from velocity components.
---
dump1090.c | 190 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
1 file changed, 182 insertions(+), 8 deletions(-)
diff --git a/dump1090.c b/dump1090.c
index 4749a78..1d60596 100644
--- a/dump1090.c
+++ b/dump1090.c
@@ -85,8 +85,17 @@ struct aircraft {
char flight[9]; /* Flight number */
int altitude; /* Altitude */
int speed; /* Velocity computed from EW and NS components. */
+ int track; /* Angle of flight. */
time_t seen; /* Time at which the last packet was received. */
long messages; /* Number of Mode S messages received. */
+ /* Encoded latitude and longitude as extracted by odd and even
+ * CPR encoded messages. */
+ int odd_cprlat;
+ int odd_cprlon;
+ int even_cprlat;
+ int even_cprlon;
+ double lat, lon; /* Coordinated obtained from CPR encoded data. */
+ time_t odd_cprtime, even_cprtime;
struct aircraft *next; /* Next aircraft in our linked list. */
};
@@ -157,14 +166,14 @@ struct modesMessage {
int heading_is_valid;
int heading;
int aircraft_type;
- int fflag; /* Odd or Even CPR message? */
+ int fflag; /* 1 = Odd, 0 = Even CPR message. */
int tflag; /* UTC synchronized? */
int raw_latitude; /* Non decoded latitude */
int raw_longitude; /* Non decoded longitude */
char flight[9]; /* 8 chars flight number. */
- int ew_dir; /* E/W direction. */
+ int ew_dir; /* 0 = East, 1 = West. */
int ew_velocity; /* E/W velocity. */
- int ns_dir; /* N/S direction. */
+ int ns_dir; /* 0 = North, 1 = South. */
int ns_velocity; /* N/S velocity. */
int vert_rate_source; /* Vertical rate source. */
int vert_rate_sign; /* Vertical rate sign. */
@@ -867,8 +876,24 @@ void decodeModesMessage(struct modesMessage *mm, unsigned char *msg) {
mm->vert_rate_source = (msg[8]&0x10) >> 4;
mm->vert_rate_sign = (msg[8]&0x8) >> 5;
mm->vert_rate = ((msg[8]&7) << 6) | ((msg[9]&0xfc) >> 2);
+ /* Compute velocity and angle from the two speed
+ * components. */
mm->velocity = sqrt(mm->ns_velocity*mm->ns_velocity+
mm->ew_velocity*mm->ew_velocity);
+ if (mm->velocity) {
+ int ewv = mm->ew_velocity;
+ int nsv = mm->ns_velocity;
+ double heading;
+
+ if (mm->ew_dir) ewv *= -1;
+ if (mm->ns_dir) nsv *= -1;
+ heading = atan2(ewv,nsv);
+
+ /* Convert to degrees. */
+ mm->heading = heading * 360 / (M_PI*2);
+ /* We don't want negative values but a 0-360 scale. */
+ if (mm->heading < 0) mm->heading += 360;
+ }
} else if (mm->mesub == 3 || mm->mesub == 4) {
mm->heading_is_valid = msg[5] & (1<<2);
mm->heading = (360.0/128) * (((msg[5] & 3) << 5) |
@@ -1207,6 +1232,15 @@ struct aircraft *interactiveCreateAircraft(uint32_t addr) {
a->flight[0] = '\0';
a->altitude = 0;
a->speed = 0;
+ a->track = 0;
+ a->odd_cprlat = 0;
+ a->odd_cprlon = 0;
+ a->odd_cprtime = 0;
+ a->even_cprlat = 0;
+ a->even_cprlon = 0;
+ a->even_cprtime = 0;
+ a->lat = 0;
+ a->lon = 0;
a->seen = time(NULL);
a->messages = 0;
a->next = NULL;
@@ -1225,6 +1259,130 @@ struct aircraft *interactiveFindAircraft(uint32_t addr) {
return NULL;
}
+/* Always positive MOD operation, used for CPR decoding. */
+int cprModFunction(int a, int b) {
+ int res = a % b;
+ if (res < 0) res += b;
+ return res;
+}
+
+/* The NL function uses the precomputed table from 1090-WP-9-14 */
+int cprNLFunction(double lat) {
+ if (lat < 10.47047130) return 59;
+ if (lat < 14.82817437) return 58;
+ if (lat < 18.18626357) return 57;
+ if (lat < 21.02939493) return 56;
+ if (lat < 23.54504487) return 55;
+ if (lat < 25.82924707) return 54;
+ if (lat < 27.93898710) return 53;
+ if (lat < 29.91135686) return 52;
+ if (lat < 31.77209708) return 51;
+ if (lat < 33.53993436) return 50;
+ if (lat < 35.22899598) return 49;
+ if (lat < 36.85025108) return 48;
+ if (lat < 38.41241892) return 47;
+ if (lat < 39.92256684) return 46;
+ if (lat < 41.38651832) return 45;
+ if (lat < 42.80914012) return 44;
+ if (lat < 44.19454951) return 43;
+ if (lat < 45.54626723) return 42;
+ if (lat < 46.86733252) return 41;
+ if (lat < 48.16039128) return 40;
+ if (lat < 49.42776439) return 39;
+ if (lat < 50.67150166) return 38;
+ if (lat < 51.89342469) return 37;
+ if (lat < 53.09516153) return 36;
+ if (lat < 54.27817472) return 35;
+ if (lat < 55.44378444) return 34;
+ if (lat < 56.59318756) return 33;
+ if (lat < 57.72747354) return 32;
+ if (lat < 58.84763776) return 31;
+ if (lat < 59.95459277) return 30;
+ if (lat < 61.04917774) return 29;
+ if (lat < 62.13216659) return 28;
+ if (lat < 63.20427479) return 27;
+ if (lat < 64.26616523) return 26;
+ if (lat < 65.31845310) return 25;
+ if (lat < 66.36171008) return 24;
+ if (lat < 67.39646774) return 23;
+ if (lat < 68.42322022) return 22;
+ if (lat < 69.44242631) return 21;
+ if (lat < 70.45451075) return 20;
+ if (lat < 71.45986473) return 19;
+ if (lat < 72.45884545) return 18;
+ if (lat < 73.45177442) return 17;
+ if (lat < 74.43893416) return 16;
+ if (lat < 75.42056257) return 15;
+ if (lat < 76.39684391) return 14;
+ if (lat < 77.36789461) return 13;
+ if (lat < 78.33374083) return 12;
+ if (lat < 79.29428225) return 11;
+ if (lat < 80.24923213) return 10;
+ if (lat < 81.19801349) return 9;
+ if (lat < 82.13956981) return 8;
+ if (lat < 83.07199445) return 7;
+ if (lat < 83.99173563) return 6;
+ if (lat < 84.89166191) return 5;
+ if (lat < 85.75541621) return 4;
+ if (lat < 86.53536998) return 3;
+ if (lat < 87.00000000) return 2;
+ else return 1;
+}
+
+int cprNFunction(int i, int isodd) {
+ int nl = cprNLFunction(i) - isodd;
+ if (nl < 1) nl = 1;
+ return nl;
+}
+
+double cprDlonFunction(int i, int isodd) {
+ return 360.0 / cprNFunction(i, isodd);
+}
+
+/* This algorithm comes from:
+ * http://www.lll.lu/~edward/edward/adsb/DecodingADSBposition.html.
+ *
+ *
+ * A few remarks:
+ * 1) 131072 is 2^17 since CPR latitude and longitude are encoded in 17 bits.
+ * 2) We assume that we always received the odd packet as last packet for
+ * simplicity. This may provide a position that is less fresh of a few
+ * seconds.
+ */
+void decodeCPR(struct aircraft *a) {
+ const double AirDlat0 = 6;
+ const double AirDlat1 = 360.0 / 59;
+ double lat0 = a->even_cprlat;
+ double lat1 = a->odd_cprlat;
+ double lon0 = a->even_cprlon;
+ double lon1 = a->odd_cprlon;
+
+ /* Compute the Latitude Index "j" */
+ int j = ((59*lat0 - 60*lat1) / 131072) + 0.5;
+ double rlat0 = AirDlat0 * (cprModFunction(j,60) + lat0 / 131072);
+ double rlat1 = AirDlat1 * (cprModFunction(j,59) + lat1 / 131072);
+
+ /* Check that both are in the same latitude zone, or abort. */
+ if (cprNLFunction(rlat0) != cprNLFunction(rlat1)) return;
+
+ /* Compute ni and the longitude index m */
+ if (a->even_cprtime > a->odd_cprtime) {
+ /* Use even packet. */
+ int ni = cprNFunction(rlat0,0);
+ int m = (((lon0 * (cprNLFunction(rlat0)-1)) -
+ (lon1 * cprNLFunction(rlat0))) / 131072) + 0.5;
+ a->lon = cprDlonFunction(rlat0,0) * (cprModFunction(m,ni)+lon0/131072);
+ a->lat = rlat0;
+ } else {
+ /* Use odd packet. */
+ int ni = cprNFunction(rlat1,1);
+ int m = (((lon0 * (cprNLFunction(rlat1)-1)) -
+ (lon1 * cprNLFunction(rlat1))) / 131072) + 0.5;
+ a->lon = cprDlonFunction(rlat1,1) * (cprModFunction(m,ni)+lon1/131072);
+ a->lat = rlat1;
+ }
+}
+
/* Receive new messages and populate the interactive mode with more info. */
void interactiveReceiveData(struct modesMessage *mm) {
uint32_t addr;
@@ -1268,9 +1426,23 @@ void interactiveReceiveData(struct modesMessage *mm) {
memcpy(a->flight, mm->flight, sizeof(a->flight));
} else if (mm->metype >= 9 && mm->metype <= 18) {
a->altitude = mm->altitude;
+ if (mm->fflag) {
+ a->odd_cprlat = mm->raw_latitude;
+ a->odd_cprlon = mm->raw_longitude;
+ a->odd_cprtime = a->seen; /* Current time. */
+ } else {
+ a->even_cprlat = mm->raw_latitude;
+ a->even_cprlon = mm->raw_longitude;
+ a->even_cprtime = a->seen; /* Current time. */
+ }
+ /* If the two data is less than 10 seconds apart, compute
+ * the position. */
+ if (abs(a->even_cprtime - a->odd_cprtime) <= 10)
+ decodeCPR(a);
} else if (mm->metype == 19) {
if (mm->mesub == 1 || mm->mesub == 2) {
a->speed = mm->velocity;
+ a->track = mm->heading;
}
}
}
@@ -1288,9 +1460,10 @@ void interactiveShowData(void) {
progress[3] = '\0';
printf("\x1b[H\x1b[2J"); /* Clear the screen */
- printf("Hex Flight Altitude Speed Messages Seen %s\n",
- progress);
- printf("-------------------------------------------------------\n");
+ printf(
+"Hex Flight Altitude Speed Lat Lon Track Messages Seen %s\n"
+"--------------------------------------------------------------------------------\n",
+ progress);
while(a && count < Modes.interactive_rows) {
int altitude = a->altitude, speed = a->speed;
@@ -1301,8 +1474,9 @@ void interactiveShowData(void) {
speed *= 1.852;
}
- printf("%-6s %-8s %-9d %-9d %-9ld %d sec ago\n",
- a->hexaddr, a->flight, altitude, speed, a->messages,
+ printf("%-6s %-8s %-9d %-7d %-7.03f %-7.03f %-3d %-9ld %d sec\n",
+ a->hexaddr, a->flight, altitude, speed,
+ a->lat, a->lon, a->track, a->messages,
(int)(now - a->seen));
a = a->next;
count++;
--
Alioth's /usr/local/bin/git-commit-notice on /srv/git.debian.org/git/pkg-hamradio/dump1090.git
More information about the pkg-hamradio-commits
mailing list