From b0c6be0a63e21e05771de89b3526bd2fe900ccf7 Mon Sep 17 00:00:00 2001
From: robertlipe <robertlipe@f51c46e8-681c-474f-0cfe-069cfd0219fb>
Date: Sun, 22 Mar 2015 00:31:17 +0000
Subject: [PATCH] Gleb Smirinoff contributes vertical speed calculation for use
 with subrip. (There are probably edge cases about tracks with and without
 valid alt....)

---
 gpsbabel/defs.h                               |  1 +
 gpsbabel/subrip.cc                            | 10 ++++++++
 gpsbabel/waypt.cc                             | 23 +++++++++++++++++++
 .../xmldoc/formats/options/subrip-format.xml  |  6 ++++-
 4 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/gpsbabel/defs.h b/gpsbabel/defs.h
index 2c284d789..6a06920db 100644
--- a/gpsbabel/defs.h
+++ b/gpsbabel/defs.h
@@ -866,6 +866,7 @@ void waypt_status_disp(int total_ct, int myct);
 double waypt_time(const Waypoint* wpt);
 double waypt_speed(const Waypoint* A, const Waypoint* B);
 double waypt_speed_ex(const Waypoint* A, const Waypoint* B);
+double waypt_vertical_speed(const Waypoint* A, const Waypoint* B);
 double waypt_course(const Waypoint* A, const Waypoint* B);
 double waypt_distance(const Waypoint* A, const Waypoint* B);
 double waypt_distance_ex(const Waypoint* A, const Waypoint* B);
diff --git a/gpsbabel/subrip.cc b/gpsbabel/subrip.cc
index ffd95f6e3..9490aadf4 100644
--- a/gpsbabel/subrip.cc
+++ b/gpsbabel/subrip.cc
@@ -33,6 +33,7 @@ static time_t time_offset;
 static int stnum;
 static gbfile* fout;
 static const Waypoint* prevwpp;
+static double vspeed;
 
 /* internal helper functions */
 
@@ -106,6 +107,9 @@ subrip_prevwp_pr(const Waypoint* waypointp)
         else
           gbfprintf(fout, "   -");
         break;
+      case 'v':
+        gbfprintf(fout, "%2.2f", vspeed);
+        break;
       case 't':
         {
           QTime t = prevwpp->GetCreationTime().toUTC().time();
@@ -159,6 +163,10 @@ subrip_trkpt_pr(const Waypoint* waypointp)
    * associated waypoint plus that of the following one.
    * Since we get waypoints one at a time, the only way is to store one and
    * defer processing until we get the next one.
+   *
+   * To determine vertical speed we need to have not only previous waypoint,
+   * but also pre-previous, so we calculate vspeed right before forgetting
+   * the previous.
    */
   if ((stnum == 1) && (time_offset == 0))
     /*
@@ -174,6 +182,7 @@ subrip_trkpt_pr(const Waypoint* waypointp)
 
   if (prevwpp) {
     subrip_prevwp_pr(waypointp);
+    vspeed = waypt_vertical_speed(waypointp, prevwpp);
   }
   prevwpp = waypointp;
 }
@@ -191,6 +200,7 @@ subrip_wr_init(const char* fname)
   time_offset = 0;
 
   prevwpp = NULL;
+  vspeed = 0;
 
   if ((opt_gpstime != NULL) && (opt_gpsdate != NULL)) {
     time(&gpstime_t);
diff --git a/gpsbabel/waypt.cc b/gpsbabel/waypt.cc
index 3cdbcdbe0..15706c5a1 100644
--- a/gpsbabel/waypt.cc
+++ b/gpsbabel/waypt.cc
@@ -541,6 +541,29 @@ waypt_speed(const Waypoint* A, const Waypoint* B)
   }
 }
 
+/*
+ * Calculates the vertical speed between points "A" and "B"
+ * the result comes in meters per second and can be negative.
+ */
+
+double
+waypt_vertical_speed(const Waypoint* A, const Waypoint* B)
+{
+  double altitude, time;
+
+  altitude = A->altitude - B->altitude;
+  if (altitude == 0) {
+    return 0;
+  }
+
+  time = fabs((double)A->creation_time.msecsTo(B->creation_time)) / 1000.0;
+  if (time > 0) {
+    return (altitude / time);
+  } else {
+    return 0;
+  }
+}
+
 /*
  * Calculates "Course True" from A to B
  */
diff --git a/gpsbabel/xmldoc/formats/options/subrip-format.xml b/gpsbabel/xmldoc/formats/options/subrip-format.xml
index 2f2b27e96..1d017a678 100644
--- a/gpsbabel/xmldoc/formats/options/subrip-format.xml
+++ b/gpsbabel/xmldoc/formats/options/subrip-format.xml
@@ -19,9 +19,13 @@
   <entry>%e</entry>
   <entry>elevation in meters</entry>
 </row>
+<row>
+  <entry>%v</entry>
+  <entry>vertical speed in m/s</entry>
+</row>
 <row>
   <entry>%t</entry>
-  <entry>tiomestamp</entry>
+  <entry>timestamp</entry>
 </row>
 <row>
   <entry>%l</entry>
-- 
2.30.2