cgps: Big clean up of code.

More comments.  Range checking of values.  Tweaked formatting.
More data in tall mode.

Thanks to the support of Virgin Orbit for this patch.

1 files changed, 292 insertions, 192 deletions

diff --git a/cgps.c b/cgps.c
index d8338800..03aa1575 100644
--- a/cgps.c
+++ b/cgps.c
@@ -84,7 +84,7 @@
 /* This is the maximum ysize we need for the 'satellites' window. */
 #define MAX_SATWIN_SIZE (MAX_POSSIBLE_SATS + SATWIN_OVERHEAD)
 
-/* Minimum xsize to display 3rd window with ECEF's, etc. */
+/* Minimum xsize to display 3rd window with DOPs, etc. */
 #define MIN_ERRWIN_SIZE 100
 
 #include <stdio.h>
@@ -122,11 +122,12 @@ static int debug;
 static WINDOW *datawin, *satellites, *messages;
 
 static bool raw_flag = false;
-static bool ecef_flag = false;      /* tall screen, show ECEF */
+static bool show_ecefs = false;     /* taller screen, show ECEFs */
+static bool show_more_dops = false;      /* tall screen, show more DOPs */
 static bool silent_flag = false;
 static bool magnetic_flag = false;
 static int window_ysize = 0;
-static int display_sats = 0;
+static int display_sats = 0;        /* number of rows of sats to display */
 #ifdef TRUENORTH
 static bool compass_flag = false;
 #endif /* TRUENORTH */
@@ -137,6 +138,61 @@ static bool compass_flag = false;
 #define GPS_ERROR	-2	/* low-level failure in GPS read */
 #define GPS_TIMEOUT	-3	/* low-level failure in GPS waiting */
 
+/* range test an int, return 5 chars + NUL */
+static const char *int_to_str(int val, int min, int max)
+{
+    static char buf[20];
+
+    if (val < min || val > max) {
+	return "  n/a";
+    }
+    (void)snprintf(buf, sizeof(buf), "%5d", val);
+    return buf;
+}
+
+/* format a DOP into a 5 char string, handle NAN, INFINITE */
+static char *dop_to_str(double dop)
+{
+    static char buf[20];
+
+    if (isfinite(dop) == 0) {
+	return " n/a ";
+    }
+    (void)snprintf(buf, sizeof(buf), "%5.2f", dop);
+    return buf;
+}
+
+/* format an EP into a string, handle NAN, INFINITE */
+static char *ep_to_str(double ep, double factor, char *units)
+{
+    static char buf[128];
+
+    if (isfinite(ep) == 0) {
+	return " n/a  ";
+    }
+    (void)snprintf(buf, sizeof(buf), "+/-%4.1f %.10s", ep * factor, units);
+    return buf;
+}
+
+/* format an ECEF p and v into a string, handle NAN, INFINITE */
+static char *ecef_to_str(double pos, double vel, double factor, char *units)
+{
+    static char buf[128];
+
+    if (isfinite(pos) == 0) {
+	if (isfinite(vel) == 0) {
+	    return "  n/a    n/a ";
+        } else {
+	    (void)snprintf(buf, sizeof(buf), "  n/a %8.3f%.4s/s",
+                           vel * factor, units);
+        }
+    } else {
+	(void)snprintf(buf, sizeof(buf), "% 14.3f%.4s %8.3f%.4s/s",
+                       pos * factor, units,  vel * factor, units);
+    }
+    return buf;
+}
+
 /* Function to call when we're all done.  Does a bit of clean-up. */
 static void die(int sig)
 {
@@ -176,25 +232,6 @@ static void die(int sig)
     exit(EXIT_SUCCESS);
 }
 
-/* format an ECEF p and v into a string, handle NAN, INFINITE */
-static char *ecef_to_str(double pos, double vel, double factor, char *units)
-{
-    static char buf[128];
-
-    if (isfinite(pos) == 0) {
-	if (isfinite(vel) == 0) {
-	    return "  n/a    n/a ";
-        } else {
-	    (void)snprintf(buf, sizeof(buf), "  n/a %8.2f%.4s/s",
-                           vel * factor, units);
-        }
-    } else {
-	(void)snprintf(buf, sizeof(buf), "% 14.4f%.4s %8.2f%.4s/s",
-                       pos * factor, units,  vel * factor, units);
-    }
-    return buf;
-}
-
 static enum deg_str_type deg_type = deg_dd;
 
 static void windowsetup(void)
@@ -220,8 +257,8 @@ static void windowsetup(void)
      * satellites (MAXCHANNELS - 2) with space still left at the bottom,
      * add a window at the bottom in which to scroll raw gpsd data.
      *
-     * 4.  If the screen is wide enough to display extra data, add a
-     * window on the right for PDOP, etc.
+     * 4.  If the screen is tall enough to display extra data, expand
+     * data window down to show DOPs, ECEFs, etc.
      */
     int xsize, ysize;
 
@@ -249,25 +286,35 @@ static void windowsetup(void)
     } else
 #endif /* TRUENORTH */
     {
-	if (ysize > MAX_GPS_DATAWIN_YSIZE + 7) {
+	if (ysize > MAX_GPS_DATAWIN_YSIZE + 10) {
+	    raw_flag = true;
+	    show_ecefs = true;
+	    show_more_dops = true;
+	    window_ysize = MAX_GPS_DATAWIN_YSIZE + 7;
+	} else if (ysize > MAX_GPS_DATAWIN_YSIZE + 6) {
 	    raw_flag = true;
-	    ecef_flag = true;
-	    window_ysize = MAX_GPS_DATAWIN_YSIZE + 3;
+	    show_ecefs = false;
+	    show_more_dops = true;
+	    window_ysize = MAX_GPS_DATAWIN_YSIZE + 4;
 	} else if (ysize > MAX_GPS_DATAWIN_YSIZE) {
 	    raw_flag = true;
-	    ecef_flag = false;
+	    show_ecefs = false;
+	    show_more_dops = false;
 	    window_ysize = MAX_GPS_DATAWIN_YSIZE;
 	} else if (ysize == MAX_GPS_DATAWIN_YSIZE) {
 	    raw_flag = false;
-	    ecef_flag = false;
+	    show_ecefs = false;
+	    show_more_dops = false;
 	    window_ysize = MAX_GPS_DATAWIN_YSIZE;
 	} else if (ysize > MIN_GPS_DATAWIN_YSIZE) {
 	    raw_flag = true;
-	    ecef_flag = false;
+	    show_ecefs = false;
+	    show_more_dops = false;
 	    window_ysize = MIN_GPS_DATAWIN_YSIZE;
 	} else if (ysize == MIN_GPS_DATAWIN_YSIZE) {
 	    raw_flag = false;
-	    ecef_flag = false;
+	    show_ecefs = false;
+	    show_more_dops = false;
 	    window_ysize = MIN_GPS_DATAWIN_YSIZE;
 	} else {
 	    (void)mvprintw(0, 0,
@@ -284,6 +331,7 @@ static void windowsetup(void)
     /* Set up the screen for either a compass or a gps receiver. */
     if (compass_flag) {
 	/* We're a compass, set up accordingly. */
+        int row = 1;
 
 	datawin = newwin(window_ysize, DATAWIN_WIDTH, 0, 0);
 	(void)nodelay(datawin, (bool) TRUE);
@@ -297,18 +345,19 @@ static void windowsetup(void)
 	(void)refresh();
 
 	/* Do the initial field label setup. */
-	(void)mvwprintw(datawin, 1, DATAWIN_DESC_OFFSET, "Time:");
-	(void)mvwprintw(datawin, 2, DATAWIN_DESC_OFFSET, "Heading:");
-	(void)mvwprintw(datawin, 3, DATAWIN_DESC_OFFSET, "Pitch:");
-	(void)mvwprintw(datawin, 4, DATAWIN_DESC_OFFSET, "Roll:");
-	(void)mvwprintw(datawin, 5, DATAWIN_DESC_OFFSET, "Dip:");
-	(void)mvwprintw(datawin, 6, DATAWIN_DESC_OFFSET, "Rcvr Type:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Time:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Heading:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Pitch:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Roll:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Dip:");
+	(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Rcvr Type:");
 	(void)wborder(datawin, 0, 0, 0, 0, 0, 0, 0, 0);
 
     } else
 #endif /* TRUENORTH */
     {
 	/* We're a GPS, set up accordingly. */
+        int row = 1;
 
 	datawin = newwin(window_ysize, DATAWIN_WIDTH, 0, 0);
 	satellites =
@@ -325,14 +374,14 @@ static void windowsetup(void)
 	(void)refresh();
 
 	/* Do the initial field label setup. */
-	(void)mvwprintw(datawin, 1, DATAWIN_DESC_OFFSET, "Time:");
-	(void)mvwprintw(datawin, 2, DATAWIN_DESC_OFFSET, "Latitude:");
-	(void)mvwprintw(datawin, 3, DATAWIN_DESC_OFFSET, "Longitude:");
-	(void)mvwprintw(datawin, 4, DATAWIN_DESC_OFFSET, "Altitude:");
-	(void)mvwprintw(datawin, 5, DATAWIN_DESC_OFFSET, "Speed:");
-	(void)mvwprintw(datawin, 6, DATAWIN_DESC_OFFSET, "Heading:");
-	(void)mvwprintw(datawin, 7, DATAWIN_DESC_OFFSET, "Climb:");
-	(void)mvwprintw(datawin, 8, DATAWIN_DESC_OFFSET, "Status:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Time:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Latitude:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Longitude:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Altitude:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Speed:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Heading:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Climb:");
+	(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET, "Status:");
 
 	/* Note that the following fields are exceptions to the
 	 * sizing rule.  The minimum window size does not include these
@@ -343,36 +392,58 @@ static void windowsetup(void)
 	 * sounded interesting. ;^) */
 
 	if (window_ysize >= MAX_GPS_DATAWIN_YSIZE) {
-	    int row = 9;
-
-            (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
-                            "Longitude Err:");
-            (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
-                            "Latitude Err:");
-            (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
-                            "Altitude Err:");
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+			    "Long Err  (XDOP, EPX):");
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+			    "Lat Err   (YDOP, EPY):");
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+			    "Alt Err   (VDOP, EPV):");
+
+	    if (show_more_dops) {
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+				"2D Err    (HDOP, CEP):");
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+				"3D Err    (PDOP, SEP):");
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+				"Time Err  (TDOP):");
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+				"Geo Err   (GDOP):");
+	    }
 
-	    if (ecef_flag){
-		(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
+	    if (show_ecefs) {
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
 				"ECEF X, VX:");
-		(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
 				"ECEF Y, VY:");
-		(void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
+		(void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
 				"ECEF Z, VZ:");
 	    }
-            (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Course Err:");
-            (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET, "Speed Err:");
 
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+			    "Speed Err (EPS):");
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
+			    "Head Err  (EPD):");
 	    /* it's actually esr that thought *these* were interesting */
-	    (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
 			    "Time offset:");
-	    (void)mvwprintw(datawin, row++, DATAWIN_DESC_OFFSET,
+	    (void)mvwaddstr(datawin, row++, DATAWIN_DESC_OFFSET,
 			    "Grid Square:");
 	}
 
 	(void)wborder(datawin, 0, 0, 0, 0, 0, 0, 0, 0);
-	/* PRN is not unique, starting at 1, for GPS, GAILEO, etc. */
-	(void)mvwprintw(satellites, 1, 1, " PRN  Elev   Azim   SNR   Used  ");
+	/* PRN is not unique for all GNSS systems.
+	 * Each GNSS (GPS, GALILEO, BeiDou, etc.) numbers their PRN from 1.
+	 * What we really have here is USI, Universal Sat ID
+	 * The USI for each GNSS satellite is unique, starting at 1.
+	 * Not all GPS receivers compute the USI the same way. YMMV
+	 *
+	 * Javad (GREIS) GPS receivers compute USI this way:
+	 * GPS is USI 1-37, GLONASS 38-70, GALILEO 71-119, SBAS 120-142,
+	 * QZSS 193-197, BeiDou 211-247
+	 *
+	 * Geostar GPS receivers compute USI this way:
+	 * GPS is USI 1 to 32, SBAS is 33 to 64, GLONASS is 65 to 96 */
+	(void)mvwaddstr(satellites, 1, 1, "  PRN  Elev   Azim   SNR  Used   ");
 	(void)wborder(satellites, 0, 0, 0, 0, 0, 0, 0, 0);
     }
 }
@@ -393,51 +464,50 @@ static void resize(int sig UNUSED)
 static void update_compass_panel(struct gps_data_t *gpsdata)
 {
     char scr[128];
+    int row = 1;
     /* Print time/date. */
     if (isfinite(gpsdata->fix.time) != 0) {
 	(void)unix_to_iso8601(gpsdata->fix.time, scr, sizeof(scr));
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, 1, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the heading. */
     if (isfinite(gpsdata->fix.track) != 0) {
 	(void)snprintf(scr, sizeof(scr), "%.1f degrees", gpsdata->fix.track);
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, 2, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the climb. */
     if (isfinite(gpsdata->fix.climb) != 0) {
 	(void)snprintf(scr, sizeof(scr), "%.2f", gpsdata->fix.climb);
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, 3, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the speed. */
     if (isfinite(gpsdata->fix.speed) != 0)
 	(void)snprintf(scr, sizeof(scr), "%.2f", gpsdata->fix.speed);
     else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, 4, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the altitude. */
     if (isfinite(gpsdata->fix.altitude) != 0)
 	(void)snprintf(scr, sizeof(scr), "%.3f", gpsdata->fix.altitude);
     else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, 5, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* When we need to fill in receiver type again, do it here. */
-    (void)mvwprintw(datawin, 6, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
-
-    /* Be quiet if the user requests silence. */
-    if (!silent_flag && raw_flag) {
-	(void)waddstr(messages, message);
-    }
+    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     (void)wrefresh(datawin);
-    if (raw_flag) {
+
+    if (raw_flag && !silent_flag) {
+	/* Be quiet if the user requests silence. */
+        (void)waddstr(messages, message);
 	(void)wrefresh(messages);
     }
 }
@@ -457,11 +527,10 @@ static int sat_cmp(const void *p1, const void *p2)
 }
 
 
-static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
+static void update_gps_panel(struct gps_data_t *gpsdata, char *message)
 /* This gets called once for each new GPS sentence. */
 {
     int newstate;
-    int row = 9;
     char scr[128], *s;
 
     /* This is for the satellite status display.  Originally lifted from
@@ -472,65 +541,59 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
     (void)mvwprintw(satellites, 1, 32, "%2d", gpsdata->satellites_used);
 
     if (gpsdata->satellites_visible != 0) {
-	int i;
+	int sat_no;
+	int loop_end = (display_sats < gpsdata->satellites_visible) ? \
+		display_sats : gpsdata->satellites_visible;
+
 	qsort( gpsdata->skyview, gpsdata->satellites_visible,
 		sizeof( struct satellite_t), sat_cmp);
-	if (display_sats >= MAX_POSSIBLE_SATS) {
-	    for (i = 0; i < MAX_POSSIBLE_SATS; i++) {
-		if (i < gpsdata->satellites_visible) {
-                    /* allow for 3 digit elevation,
-                     * ublox uses -91 to signal something undocumented */
-		    (void)snprintf(scr, sizeof(scr),
-				   " %3d   %3d    %3d    %2d      %c",
-				   gpsdata->skyview[i].PRN,
-				   gpsdata->skyview[i].elevation,
-				   gpsdata->skyview[i].azimuth,
-				   (int)gpsdata->skyview[i].ss,
-				   gpsdata->skyview[i].used ? 'Y' : 'N');
-		} else {
-		    (void)strlcpy(scr, "", sizeof(scr));
-		}
-		(void)mvwprintw(satellites, i + 2, 1, "%-*s",
-				SATELLITES_WIDTH - 3, scr);
-	    }
-	} else {
-	    int n = 0;
-	    for (i = 0; i < MAX_POSSIBLE_SATS; i++) {
-		if (n < display_sats) {
-		    if ((i < gpsdata->satellites_visible)
-			&& (gpsdata->skyview[i].used
-			    || (gpsdata->satellites_visible <= display_sats))) {
-			(void)snprintf(scr, sizeof(scr),
-				       " %3d    %2d    %3d    %2d      %c",
-				       gpsdata->skyview[i].PRN,
-				       gpsdata->skyview[i].elevation,
-				       gpsdata->skyview[i].azimuth,
-				       (int)gpsdata->skyview[i].ss,
-				       gpsdata->skyview[i].used ? 'Y' : 'N');
-			(void)mvwprintw(satellites, n + 2, 1, "%-*s",
-					SATELLITES_WIDTH - 3, scr);
-			n++;
-		    }
-		}
-	    }
+	/* displayed all sats that fit, maybe all of them */
+	for (sat_no = 0; sat_no < loop_end; sat_no++) {
+	    int column = 1;     /* column to write to */
+
+	    /* no GPS uses PRN 0, some use 255 for 'unknown'
+	     * u-blox uses PRN  1-255, NMEA 4.0 uses 1-437 */
+	    (void)mvwaddstr(satellites, sat_no + 2, column,
+			    int_to_str(gpsdata->skyview[sat_no].PRN,
+			               1, 438));
+	    /* u-blox uses -91 to signal something undocumented */
+	    column += 6;
+	    (void)mvwaddstr(satellites, sat_no + 2, column,
+			    int_to_str(gpsdata->skyview[sat_no].elevation,
+			               -90, 90));
+	    column += 7;
+	    (void)mvwaddstr(satellites, sat_no + 2, column,
+			    int_to_str(gpsdata->skyview[sat_no].azimuth,
+                                       0, 359));
+	    column += 6;
+	    (void)mvwaddstr(satellites, sat_no + 2, column,
+			    int_to_str((int)round(gpsdata->skyview[sat_no].ss),
+			               0, 254));
+	    column += 6;
+	    (void)mvwprintw(satellites, sat_no + 2, column, "    %c",
+			    gpsdata->skyview[sat_no].used ? 'Y' : 'N');
+	}
 
-	    if (n < display_sats) {
-		for (i = n; i <= display_sats; i++) {
-		    (void)mvwprintw(satellites, i + 2, 1, "%-*s",
-				    SATELLITES_WIDTH - 3, "");
-		}
+        /* last line is either blank, or More... */
+        if (sat_no < gpsdata->satellites_visible) {
+	    /* Too many sats to show them all, tell the user. */
+	    (void)mvwprintw(satellites, sat_no + 2, 1, "%-*s",
+			    SATELLITES_WIDTH - 3, "More...");
+	} else {
+	    /* Clear old data from the unused lines at bottom. */
+	    for ( ; sat_no <= display_sats; sat_no++) {
+		(void)mvwprintw(satellites, sat_no + 2, 1, "%-*s",
+				SATELLITES_WIDTH - 3, "");
 	    }
-
 	}
     }
 
-    row = 1;
     /* Print time/date. */
     if (isfinite(gpsdata->fix.time) != 0) {
 	(void)unix_to_iso8601(gpsdata->fix.time, scr, sizeof(scr));
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 1, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
 
     /* Fill in the latitude. */
@@ -539,8 +602,8 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
 		       deg_to_str(deg_type, fabs(gpsdata->fix.latitude)),
 		       (gpsdata->fix.latitude < 0) ? 'S' : 'N');
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 2, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the longitude. */
     if (gpsdata->fix.mode >= MODE_2D && isfinite(gpsdata->fix.longitude) != 0) {
@@ -548,24 +611,24 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
 		       deg_to_str(deg_type, fabs(gpsdata->fix.longitude)),
 		       (gpsdata->fix.longitude < 0) ? 'W' : 'E');
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 3, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the altitude. */
     if (gpsdata->fix.mode >= MODE_3D && isfinite(gpsdata->fix.altitude) != 0)
 	(void)snprintf(scr, sizeof(scr), "%9.3f %s",
 		       gpsdata->fix.altitude * altfactor, altunits);
     else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 4, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the speed. */
     if (gpsdata->fix.mode >= MODE_2D && isfinite(gpsdata->fix.track) != 0)
 	(void)snprintf(scr, sizeof(scr), "%8.2f %s",
 		       gpsdata->fix.speed * speedfactor, speedunits);
     else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 5, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the heading. */
     if (gpsdata->fix.mode >= MODE_2D && isfinite(gpsdata->fix.track) != 0) {
@@ -580,16 +643,16 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
 		magheading);
 	}
     } else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "  %-*s", 25, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 6, DATAWIN_VALUE_OFFSET, "  %-*s", 25, scr);
 
     /* Fill in the rate of climb. */
     if (gpsdata->fix.mode >= MODE_3D && isfinite(gpsdata->fix.climb) != 0)
 	(void)snprintf(scr, sizeof(scr), "%8.2f %s/min",
 		       gpsdata->fix.climb * altfactor * 60, altunits);
     else
-	(void)snprintf(scr, sizeof(scr), "    n/a");
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
+	(void)snprintf(scr, sizeof(scr), "n/a");
+    (void)mvwprintw(datawin, 7, DATAWIN_VALUE_OFFSET, "%-*s", 27, scr);
 
     /* Fill in the GPS status and the time since the last state
      * change. */
@@ -617,7 +680,7 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
 	    break;
 	}
     }
-    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 1, "%-*s", 26, scr);
+    (void)mvwprintw(datawin, 8, DATAWIN_VALUE_OFFSET + 1, "%-*s", 26, scr);
 
     /* Note that the following fields are exceptions to the
      * sizing rule.  The minimum window size does not include these
@@ -628,36 +691,79 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
      * sounded interesting. ;^) */
 
     if (window_ysize >= (MIN_GPS_DATAWIN_YSIZE + 5)) {
-	/* Fill in the estimated horizontal position error. */
-	if (isfinite(gpsdata->fix.epx) != 0)
-	    (void)snprintf(scr, sizeof(scr), "+/- %d %s",
-			   (int)(gpsdata->fix.epx * altfactor), altunits);
-	else
-	    (void)snprintf(scr, sizeof(scr), "  n/a");
-	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 5, "%-*s", 22,
-			scr);
-
-	if (isfinite(gpsdata->fix.epy) != 0)
-	    (void)snprintf(scr, sizeof(scr), "+/- %d %s",
-			   (int)(gpsdata->fix.epy * altfactor), altunits);
-	else
-	    (void)snprintf(scr, sizeof(scr), "  n/a");
-	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 5, "%-*s", 22,
-			scr);
+	int row = 9;
+	char *ep_str = NULL;
+	char *dop_str = NULL;
+
+	/* Fill in the estimated latitude position error, XDOP. */
+	ep_str = ep_to_str(gpsdata->fix.epx, altfactor, altunits);
+	dop_str = dop_to_str(gpsdata->dop.xdop);
+	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%s, %-*s",
+			dop_str, 11, ep_str);
+
+	/* Fill in the estimated longitude position error, YDOP. */
+	ep_str = ep_to_str(gpsdata->fix.epy, altfactor, altunits);
+	dop_str = dop_to_str(gpsdata->dop.ydop);
+	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%s, %-*s",
+			dop_str, 11, ep_str);
+
+	/* Fill in the estimated velocity error, VDOP. */
+	ep_str = ep_to_str(gpsdata->fix.epv, altfactor, altunits);
+	dop_str = dop_to_str(gpsdata->dop.vdop);
+	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%s, %-*s",
+			dop_str, 11, ep_str);
+
+	/* extra tall screen, show more DOPs */
+	if (show_more_dops) {
+	    double cep = NAN;  /* 2D EP */
+	    double sep = NAN;  /* 3D EP */
+
+	    /* Calculate estimated 2D circular position error, CEP */
+	    if (isfinite(gpsdata->fix.epy) != 0
+		&& isfinite(gpsdata->fix.epy) != 0) {
+		/* http://gauss.gge.unb.ca/papers.pdf/gpsworld.may99.pdf */
+		/* CEP is just the hypotenuse of the triangle of epx and epy */
+		cep = sqrt((gpsdata->fix.epx * gpsdata->fix.epx) +
+			   (gpsdata->fix.epy * gpsdata->fix.epy));
+		if (isfinite(gpsdata->fix.epv) != 0) {
+                    /* SEP is the spherical (3D) error probability.
+                     * The square root of the sum of the squares of epx, epy,
+                     * and epv */
+		    sep = sqrt((gpsdata->fix.epx * gpsdata->fix.epx) +
+			       (gpsdata->fix.epy * gpsdata->fix.epy) +
+			       (gpsdata->fix.epv * gpsdata->fix.epv));
+		}
+	    }
 
-	/* Fill in the estimated vertical position error. */
-	if (isfinite(gpsdata->fix.epv) != 0)
-	    (void)snprintf(scr, sizeof(scr), "+/- %d %s",
-			   (int)(gpsdata->fix.epv * altfactor), altunits);
-	else
-	    (void)snprintf(scr, sizeof(scr), "  n/a");
-	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 5, "%-*s", 22,
-			scr);
+	    /* Fill in the estimated horizontal (2D) error, HDOP */
+	    ep_str = ep_to_str(cep, altfactor, altunits);
+	    dop_str = dop_to_str(gpsdata->dop.hdop);
+	    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8,
+			    "%s, %-*s", dop_str, 11, ep_str);
+
+	    /* (spherical) position error, 3D error, PDOP */
+	    ep_str = ep_to_str(sep, altfactor, altunits);
+	    dop_str = dop_to_str(gpsdata->dop.pdop);
+	    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8,
+			    "%s, %-*s", dop_str, 11, ep_str);
+
+	    /* time dilution of precision, TDOP */
+	    /* FIXME: time ep? */
+	    dop_str = dop_to_str(gpsdata->dop.tdop);
+	    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%-*s",
+			    18, dop_str);
+
+	    /* geometric dilution of precision, GDOP */
+	    /* FIXME: gdop ep? */
+	    dop_str = dop_to_str(gpsdata->dop.gdop);
+	    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%-*s",
+			    18, dop_str);
 
+	}
 
-	/* extra large screen, show more ECEF */
-	if (ecef_flag) {
-            char *estr;
+        /* extra large screen, show ECEF */
+        if (show_ecefs) {
+	    char *estr;
 
 	    /* Fill in the ECEF's. */
 	    estr = ecef_to_str(gpsdata->fix.ecef.x, gpsdata->fix.ecef.vx,
@@ -674,32 +780,26 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
                                1, " m");
 	    (void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET - 3, "%-*s",
                             27, estr);
-	}
+        }
 
-	/* Fill in the estimated track error. */
-	if (isfinite(gpsdata->fix.epd) != 0)
-	    (void)snprintf(scr, sizeof(scr), "+/- %d deg",
-			   (int)(gpsdata->fix.epd));
-	else
-	    (void)snprintf(scr, sizeof(scr), "  n/a");
-	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 5, "%-*s", 22,
-			scr);
 
- 	/* Fill in the estimated speed error. */
-        if (isfinite(gpsdata->fix.eps) != 0)
- 	    (void)snprintf(scr, sizeof(scr), "+/- %d %s",
- 			   (int)(gpsdata->fix.eps * speedfactor), speedunits);
- 	else
- 	    (void)snprintf(scr, sizeof(scr), "  n/a");
- 	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 5, "%-*s", 22,
-			scr);
+	/* Fill in the estimated speed error, EPS. */
+	ep_str = ep_to_str(gpsdata->fix.eps, speedfactor, speedunits);
+	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8,
+			"       %-*s", 11,
+			ep_str);
+
+	/* Fill in the estimated track error, EPD. */
+	ep_str = ep_to_str(gpsdata->fix.epd, speedfactor, "deg");
+	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%-*s", 18,
+			ep_str);
 
-	/* Fill in the time offset, milli seconds. */
+	/* Fill in the time offset, milliseconds. */
 	if (isfinite(gpsdata->fix.time) != 0)
 	    (void)snprintf(scr, sizeof(scr), "%6.3f sec",
 			   (double)(timestamp()-gpsdata->fix.time));
 	else
-	    (void)snprintf(scr, sizeof(scr), "  n/a");
+	    (void)snprintf(scr, sizeof(scr), " n/a");
 	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 8, "%-*s", 18,
 			scr);
 	/* Fill in the grid square (esr thought *this* one was interesting). */
@@ -707,7 +807,7 @@ static void update_gps_panel(struct gps_data_t *gpsdata, char * message)
 	     isfinite(gpsdata->fix.latitude) != 0))
 	    s = maidenhead(gpsdata->fix.latitude,gpsdata->fix.longitude);
 	else
-	    s = "  n/a";
+	    s = "n/a";
 	(void)mvwprintw(datawin, row++, DATAWIN_VALUE_OFFSET + 9, "%-*s",
 			18, s);
 
@@ -890,14 +990,14 @@ int main(int argc, char *argv[])
 
 	/* wait 1/2 second for gpsd */
 	if (!gps_waiting(&gpsdata, 500000)) {
-	    /* 240 tries at .5 Sec a try is a 2 minute timeout */
+	    /* 240 tries at 0.5 seconds a try is a 2 minute timeout */
 	    if ( 240 < wait_clicks++ )
 		die(GPS_TIMEOUT);
 	} else {
 	    wait_clicks = 0;
 	    errno = 0;
             *message = '\0';
-           if (gps_read(&gpsdata, message, sizeof(message)) == -1) {
+	    if (gps_read(&gpsdata, message, sizeof(message)) == -1) {
 		(void)fprintf(stderr, "cgps: socket error 4\n");
 		die(errno == 0 ? GPS_GONE : GPS_ERROR);
 	    } else {