X-Git-Url: https://git.street.me.uk/andy/viking.git/blobdiff_plain/24d5c7e28cd8a8f90bc51562dcec0234a455a528..4a050412da32aa6f237c358cfa0c5a3775f21e9a:/src/viktrack.c

diff --git a/src/viktrack.c b/src/viktrack.c
index b550ef78..6eb685ad 100644
--- a/src/viktrack.c
+++ b/src/viktrack.c
@@ -18,20 +18,29 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  *
  */
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
 
 #include <glib.h>
 #include <time.h>
-#include <stdio.h>
+#include <stdlib.h>
+#ifdef HAVE_STRING_H
+#include <string.h>
+#endif
+#ifdef HAVE_MATH_H
+#include <math.h>
+#endif
+
 #include "coords.h"
 #include "vikcoord.h"
 #include "viktrack.h"
 #include "globals.h"
+#include "dems.h"
 
 VikTrack *vik_track_new()
 {
-  VikTrack *tr = g_malloc ( sizeof ( VikTrack ) );
-  tr->trackpoints = NULL;
-  tr->comment = NULL;
+  VikTrack *tr = g_malloc0 ( sizeof ( VikTrack ) );
   tr->ref_count = 1;
   return tr;
 }
@@ -60,6 +69,17 @@ void vik_track_ref(VikTrack *tr)
   tr->ref_count++;
 }
 
+void vik_track_set_property_dialog(VikTrack *tr, GtkWidget *dialog)
+{
+  /* Warning: does not check for existing dialog */
+  tr->property_dialog = dialog;
+}
+
+void vik_track_clear_property_dialog(VikTrack *tr)
+{
+  tr->property_dialog = NULL;
+}
+
 void vik_track_free(VikTrack *tr)
 {
   if ( tr->ref_count-- > 1 )
@@ -69,6 +89,9 @@ void vik_track_free(VikTrack *tr)
     g_free ( tr->comment );
   g_list_foreach ( tr->trackpoints, (GFunc) g_free, NULL );
   g_list_free( tr->trackpoints );
+  if (tr->property_dialog)
+    if ( GTK_IS_WIDGET(tr->property_dialog) )
+      gtk_widget_destroy ( GTK_WIDGET(tr->property_dialog) );
   g_free ( tr );
 }
 
@@ -92,7 +115,14 @@ VikTrack *vik_track_copy ( const VikTrack *tr )
 
 VikTrackpoint *vik_trackpoint_new()
 {
-  return g_malloc0(sizeof(VikTrackpoint));
+  VikTrackpoint *tp = g_malloc0(sizeof(VikTrackpoint));
+  tp->speed = NAN;
+  tp->course = NAN;
+  tp->altitude = VIK_DEFAULT_ALTITUDE;
+  tp->hdop = VIK_DEFAULT_DOP;
+  tp->vdop = VIK_DEFAULT_DOP;
+  tp->pdop = VIK_DEFAULT_DOP;
+  return tp;
 }
 
 void vik_trackpoint_free(VikTrackpoint *tp)
@@ -324,6 +354,9 @@ gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
 
   GList *iter = tr->trackpoints;
 
+  if (!iter || !iter->next) /* zero- or one-point track */
+	  return NULL;
+
   { /* test if there's anything worth calculating */
     gboolean okay = FALSE;
     while ( iter )
@@ -337,7 +370,7 @@ gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
       return NULL;
   }
 
-
+  iter = tr->trackpoints;
 
   g_assert ( num_chunks < 16000 );
 
@@ -346,6 +379,12 @@ gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
   total_length = vik_track_get_length_including_gaps ( tr );
   chunk_length = total_length / num_chunks;
 
+  /* Zero chunk_length (eg, track of 2 tp with the same loc) will cause crash */
+  if (chunk_length <= 0) {
+    g_free(pts);
+    return NULL;
+  }
+
   current_dist = 0.0;
   current_area_under_curve = 0;
   current_chunk = 0;
@@ -373,7 +412,8 @@ gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
        **/
 
       if ( ignore_it )
-        pts[current_chunk] = VIK_DEFAULT_ALTITUDE;
+	// Seemly can't determine average for this section - so use last known good value (much better than just sticking in zero)
+        pts[current_chunk] = altitude1;
       else
         pts[current_chunk] = altitude1 + (altitude2-altitude1)*((dist_along_seg - (chunk_length/2))/current_seg_length);
 
@@ -408,6 +448,12 @@ gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
       dist_along_seg = chunk_length - current_dist;
       if ( ignore_it || !iter->next ) {
         pts[current_chunk] = current_area_under_curve / current_dist;
+        if (!iter->next) {
+          int i;
+          for (i = current_chunk + 1; i < num_chunks; i++)
+            pts[i] = pts[current_chunk];
+          break;
+        }
       } 
       else {
         current_area_under_curve += dist_along_seg * (altitude1 + (altitude2 - altitude1)*dist_along_seg/current_seg_length);
@@ -427,7 +473,7 @@ void vik_track_get_total_elevation_gain(const VikTrack *tr, gdouble *up, gdouble
 {
   gdouble diff;
   *up = *down = 0;
-  if ( tr->trackpoints )
+  if ( tr->trackpoints && VIK_TRACKPOINT(tr->trackpoints->data)->altitude != VIK_DEFAULT_ALTITUDE )
   {
     GList *iter = tr->trackpoints->next;
     while (iter)
@@ -439,17 +485,19 @@ void vik_track_get_total_elevation_gain(const VikTrack *tr, gdouble *up, gdouble
         *down -= diff;
       iter = iter->next;
     }
-  }
+  } else
+    *up = *down = VIK_DEFAULT_ALTITUDE;
 }
 
+
+/* by Alex Foobarian */
 gdouble *vik_track_make_speed_map ( const VikTrack *tr, guint16 num_chunks )
 {
-  gdouble *pts;
-  gdouble duration, chunk_dur, t;
+  gdouble *v, *s, *t;
+  gdouble duration, chunk_dur;
   time_t t1, t2;
-  int i;
-
-  GList *iter = tr->trackpoints;
+  int i, pt_count, numpts, index;
+  GList *iter;
 
   if ( ! tr->trackpoints )
     return NULL;
@@ -464,56 +512,629 @@ gdouble *vik_track_make_speed_map ( const VikTrack *tr, guint16 num_chunks )
     return NULL;
 
   if (duration < 0) {
-    fprintf(stderr, "negative duration: unsorted trackpoint timestamps?\n");
+    g_warning("negative duration: unsorted trackpoint timestamps?");
     return NULL;
   }
-  
-  pts = g_malloc ( sizeof(gdouble) * num_chunks );
+  pt_count = vik_track_get_tp_count(tr);
 
+  v = g_malloc ( sizeof(gdouble) * num_chunks );
   chunk_dur = duration / num_chunks;
-  t = t1;
-  for (i = 0; i < num_chunks; i++, t+=chunk_dur) {
-    while (iter && VIK_TRACKPOINT(iter->data)->timestamp <= t) {
-      iter = iter->next;
+
+  s = g_malloc(sizeof(double) * pt_count);
+  t = g_malloc(sizeof(double) * pt_count);
+
+  iter = tr->trackpoints->next;
+  numpts = 0;
+  s[0] = 0;
+  t[0] = VIK_TRACKPOINT(iter->prev->data)->timestamp;
+  numpts++;
+  while (iter) {
+    s[numpts] = s[numpts-1] + vik_coord_diff ( &(VIK_TRACKPOINT(iter->prev->data)->coord), &(VIK_TRACKPOINT(iter->data)->coord) );
+    t[numpts] = VIK_TRACKPOINT(iter->data)->timestamp;
+    numpts++;
+    iter = iter->next;
+  }
+
+  /* In the following computation, we iterate through periods of time of duration chunk_dur.
+   * The first period begins at the beginning of the track.  The last period ends at the end of the track.
+   */
+  index = 0; /* index of the current trackpoint. */
+  for (i = 0; i < num_chunks; i++) {
+    /* we are now covering the interval from t[0] + i*chunk_dur to t[0] + (i+1)*chunk_dur.
+     * find the first trackpoint outside the current interval, averaging the speeds between intermediate trackpoints.
+     */
+    if (t[0] + i*chunk_dur >= t[index]) {
+      gdouble acc_t = 0, acc_s = 0;
+      while (t[0] + i*chunk_dur >= t[index]) {
+	acc_s += (s[index+1]-s[index]);
+	acc_t += (t[index+1]-t[index]);
+	index++;
+      }
+      v[i] = acc_s/acc_t;
+    } 
+    else if (i) {
+      v[i] = v[i-1];
+    }
+    else {
+      v[i] = 0;
+    }
+  }
+  g_free(s);
+  g_free(t);
+  return v;
+}
+
+/**
+ * Make a distance/time map, heavily based on the vik_track_make_speed_map method
+ */
+gdouble *vik_track_make_distance_map ( const VikTrack *tr, guint16 num_chunks )
+{
+  gdouble *v, *s, *t;
+  gdouble duration, chunk_dur;
+  time_t t1, t2;
+  int i, pt_count, numpts, index;
+  GList *iter;
+
+  if ( ! tr->trackpoints )
+    return NULL;
+
+  t1 = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
+  t2 = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
+  duration = t2 - t1;
+
+  if ( !t1 || !t2 || !duration )
+    return NULL;
+
+  if (duration < 0) {
+    g_warning("negative duration: unsorted trackpoint timestamps?");
+    return NULL;
+  }
+  pt_count = vik_track_get_tp_count(tr);
+
+  v = g_malloc ( sizeof(gdouble) * num_chunks );
+  chunk_dur = duration / num_chunks;
+
+  s = g_malloc(sizeof(double) * pt_count);
+  t = g_malloc(sizeof(double) * pt_count);
+
+  iter = tr->trackpoints->next;
+  numpts = 0;
+  s[0] = 0;
+  t[0] = VIK_TRACKPOINT(iter->prev->data)->timestamp;
+  numpts++;
+  while (iter) {
+    s[numpts] = s[numpts-1] + vik_coord_diff ( &(VIK_TRACKPOINT(iter->prev->data)->coord), &(VIK_TRACKPOINT(iter->data)->coord) );
+    t[numpts] = VIK_TRACKPOINT(iter->data)->timestamp;
+    numpts++;
+    iter = iter->next;
+  }
+
+  /* In the following computation, we iterate through periods of time of duration chunk_dur.
+   * The first period begins at the beginning of the track.  The last period ends at the end of the track.
+   */
+  index = 0; /* index of the current trackpoint. */
+  for (i = 0; i < num_chunks; i++) {
+    /* we are now covering the interval from t[0] + i*chunk_dur to t[0] + (i+1)*chunk_dur.
+     * find the first trackpoint outside the current interval, averaging the distance between intermediate trackpoints.
+     */
+    if (t[0] + i*chunk_dur >= t[index]) {
+      gdouble acc_s = 0; // No need for acc_t
+      while (t[0] + i*chunk_dur >= t[index]) {
+	acc_s += (s[index+1]-s[index]);
+	index++;
+      }
+      // The only bit that's really different from the speed map - just keep an accululative record distance
+      v[i] = i ? v[i-1]+acc_s : acc_s;
+    }
+    else if (i) {
+      v[i] = v[i-1];
+    }
+    else {
+      v[i] = 0;
+    }
+  }
+  g_free(s);
+  g_free(t);
+  return v;
+}
+
+/**
+ * This uses the 'time' based method to make the graph, (which is a simpler compared to the elevation/distance)
+ * This results in a slightly blocky graph when it does not have many trackpoints: <60
+ * NB Somehow the elevation/distance applies some kind of smoothing algorithm,
+ *   but I don't think any one understands it any more (I certainly don't ATM)
+ */
+gdouble *vik_track_make_elevation_time_map ( const VikTrack *tr, guint16 num_chunks )
+{
+  time_t t1, t2;
+  gdouble duration, chunk_dur;
+  GList *iter = tr->trackpoints;
+
+  if (!iter || !iter->next) /* zero- or one-point track */
+    return NULL;
+
+  /* test if there's anything worth calculating */
+  gboolean okay = FALSE;
+  while ( iter ) {
+    if ( VIK_TRACKPOINT(iter->data)->altitude != VIK_DEFAULT_ALTITUDE ) {
+      okay = TRUE;
+      break;
+    }
+    iter = iter->next;
+  }
+  if ( ! okay )
+    return NULL;
+
+  t1 = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
+  t2 = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
+  duration = t2 - t1;
+
+  if ( !t1 || !t2 || !duration )
+    return NULL;
+
+  if (duration < 0) {
+    g_warning("negative duration: unsorted trackpoint timestamps?");
+    return NULL;
+  }
+  gint pt_count = vik_track_get_tp_count(tr);
+
+  // Reset iterator back to the beginning
+  iter = tr->trackpoints;
+
+  gdouble *pts = g_malloc ( sizeof(gdouble) * num_chunks ); // The return altitude values
+  gdouble *s = g_malloc(sizeof(double) * pt_count); // calculation altitudes
+  gdouble *t = g_malloc(sizeof(double) * pt_count); // calculation times
+
+  chunk_dur = duration / num_chunks;
+
+  s[0] = VIK_TRACKPOINT(iter->data)->altitude;
+  t[0] = VIK_TRACKPOINT(iter->data)->timestamp;
+  iter = tr->trackpoints->next;
+  gint numpts = 1;
+  while (iter) {
+    s[numpts] = VIK_TRACKPOINT(iter->data)->altitude;
+    t[numpts] = VIK_TRACKPOINT(iter->data)->timestamp;
+    numpts++;
+    iter = iter->next;
+  }
+
+ /* In the following computation, we iterate through periods of time of duration chunk_dur.
+   * The first period begins at the beginning of the track.  The last period ends at the end of the track.
+   */
+  gint index = 0; /* index of the current trackpoint. */
+  gint i;
+  for (i = 0; i < num_chunks; i++) {
+    /* we are now covering the interval from t[0] + i*chunk_dur to t[0] + (i+1)*chunk_dur.
+     * find the first trackpoint outside the current interval, averaging the heights between intermediate trackpoints.
+     */
+    if (t[0] + i*chunk_dur >= t[index]) {
+      gdouble acc_s = s[index]; // initialise to first point
+      while (t[0] + i*chunk_dur >= t[index]) {
+	acc_s += (s[index+1]-s[index]);
+	index++;
+      }
+      pts[i] = acc_s;
+    }
+    else if (i) {
+      pts[i] = pts[i-1];
+    }
+    else {
+      pts[i] = 0;
     }
-    pts[i] = vik_coord_diff ( &(VIK_TRACKPOINT(iter->prev->data)->coord),
-					  &(VIK_TRACKPOINT(iter->data)->coord) ) / 
-      (gdouble)(VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(iter->prev->data)->timestamp);
   }
+  g_free(s);
+  g_free(t);
 
   return pts;
 }
 
-VikCoord *vik_track_get_closest_tp_by_percentage_dist ( VikTrack *tr, gdouble reldist )
+/**
+ * Make a speed/distance map
+ */
+gdouble *vik_track_make_speed_dist_map ( const VikTrack *tr, guint16 num_chunks )
+{
+  gdouble *v, *s, *t;
+  time_t t1, t2;
+  gint i, pt_count, numpts, index;
+  GList *iter;
+  gdouble duration, total_length, chunk_length;
+
+  if ( ! tr->trackpoints )
+    return NULL;
+
+  t1 = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
+  t2 = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
+  duration = t2 - t1;
+
+  if ( !t1 || !t2 || !duration )
+    return NULL;
+
+  if (duration < 0) {
+    g_warning("negative duration: unsorted trackpoint timestamps?");
+    return NULL;
+  }
+
+  total_length = vik_track_get_length_including_gaps ( tr );
+  chunk_length = total_length / num_chunks;
+  pt_count = vik_track_get_tp_count(tr);
+
+  if (chunk_length <= 0) {
+    return NULL;
+  }
+
+  v = g_malloc ( sizeof(gdouble) * num_chunks );
+  s = g_malloc ( sizeof(double) * pt_count );
+  t = g_malloc ( sizeof(double) * pt_count );
+
+  // No special handling of segments ATM...
+  iter = tr->trackpoints->next;
+  numpts = 0;
+  s[0] = 0;
+  t[0] = VIK_TRACKPOINT(iter->prev->data)->timestamp;
+  numpts++;
+  while (iter) {
+    s[numpts] = s[numpts-1] + vik_coord_diff ( &(VIK_TRACKPOINT(iter->prev->data)->coord), &(VIK_TRACKPOINT(iter->data)->coord) );
+    t[numpts] = VIK_TRACKPOINT(iter->data)->timestamp;
+    numpts++;
+    iter = iter->next;
+  }
+
+  // Iterate through a portion of the track to get an average speed for that part
+  // This will essentially interpolate between segments, which I think is right given the usage of 'get_length_including_gaps'
+  index = 0; /* index of the current trackpoint. */
+  for (i = 0; i < num_chunks; i++) {
+    // Similar to the make_speed_map, but instead of using a time chunk, use a distance chunk
+    if (s[0] + i*chunk_length >= s[index]) {
+      gdouble acc_t = 0, acc_s = 0;
+      while (s[0] + i*chunk_length >= s[index]) {
+	acc_s += (s[index+1]-s[index]);
+	acc_t += (t[index+1]-t[index]);
+	index++;
+      }
+      v[i] = acc_s/acc_t;
+    }
+    else if (i) {
+      v[i] = v[i-1];
+    }
+    else {
+      v[i] = 0;
+    }
+  }
+  g_free(s);
+  g_free(t);
+  return v;
+}
+
+/* by Alex Foobarian */
+VikTrackpoint *vik_track_get_closest_tp_by_percentage_dist ( VikTrack *tr, gdouble reldist, gdouble *meters_from_start )
 {
   gdouble dist = vik_track_get_length_including_gaps(tr) * reldist;
   gdouble current_dist = 0.0;
   gdouble current_inc = 0.0;
-  VikCoord *rv;
   if ( tr->trackpoints )
   {
     GList *iter = tr->trackpoints->next;
+    GList *last_iter = NULL;
+    gdouble last_dist = 0.0;
     while (iter)
     {
       current_inc = vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
                                      &(VIK_TRACKPOINT(iter->prev->data)->coord) );
+      last_dist = current_dist;
       current_dist += current_inc;
       if ( current_dist >= dist )
         break;
+      last_iter = iter;
       iter = iter->next;
     }
+    if (!iter) { /* passing the end the track */
+      if (last_iter) {
+        if (meters_from_start)
+          *meters_from_start = last_dist;
+        return(VIK_TRACKPOINT(last_iter->data));
+      }
+      else
+        return NULL;
+    }
     /* we've gone past the dist already, was prev trackpoint closer? */
     /* should do a vik_coord_average_weighted() thingy. */
-    if ( iter->prev && abs(current_dist-current_inc-dist) < abs(current_dist-dist) )
+    if ( iter->prev && abs(current_dist-current_inc-dist) < abs(current_dist-dist) ) {
+      if (meters_from_start)
+        *meters_from_start = last_dist;
       iter = iter->prev;
+    }
+    else
+      if (meters_from_start)
+        *meters_from_start = current_dist;
+
+    return VIK_TRACKPOINT(iter->data);
 
+  }
+  return NULL;
+}
 
+VikTrackpoint *vik_track_get_closest_tp_by_percentage_time ( VikTrack *tr, gdouble reltime, time_t *seconds_from_start )
+{
+  time_t t_pos, t_start, t_end, t_total;
+  t_start = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
+  t_end = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
+  t_total = t_end - t_start;
 
-    rv = g_malloc(sizeof(VikCoord));
-    *rv = VIK_TRACKPOINT(iter->data)->coord;
+  t_pos = t_start + t_total * reltime;
 
-    return rv;
+  if ( !tr->trackpoints )
+    return NULL;
 
+  GList *iter = tr->trackpoints;
+
+  while (iter) {
+    if (VIK_TRACKPOINT(iter->data)->timestamp == t_pos)
+      break;
+    if (VIK_TRACKPOINT(iter->data)->timestamp > t_pos) {
+      if (iter->prev == NULL)  /* first trackpoint */
+        break;
+      time_t t_before = t_pos - VIK_TRACKPOINT(iter->prev)->timestamp;
+      time_t t_after = VIK_TRACKPOINT(iter->data)->timestamp - t_pos;
+      if (t_before <= t_after)
+        iter = iter->prev;
+      break;
+    }
+    else if ((iter->next == NULL) && (t_pos < (VIK_TRACKPOINT(iter->data)->timestamp + 3))) /* last trackpoint: accommodate for round-off */
+      break;
+    iter = iter->next;
   }
-  return NULL;
+
+  if (!iter)
+    return NULL;
+  if (seconds_from_start)
+    *seconds_from_start = VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
+  return VIK_TRACKPOINT(iter->data);
+}
+
+VikTrackpoint* vik_track_get_tp_by_max_speed ( const VikTrack *tr )
+{
+  gdouble maxspeed = 0.0, speed = 0.0;
+
+  if ( !tr->trackpoints )
+    return NULL;
+
+  GList *iter = tr->trackpoints;
+  VikTrackpoint *max_speed_tp = NULL;
+
+  while (iter) {
+    if (iter->prev) {
+      if ( VIK_TRACKPOINT(iter->data)->has_timestamp &&
+	   VIK_TRACKPOINT(iter->prev->data)->has_timestamp &&
+	   (! VIK_TRACKPOINT(iter->data)->newsegment) ) {
+	speed =  vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord), &(VIK_TRACKPOINT(iter->prev->data)->coord) )
+	  / ABS(VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(iter->prev->data)->timestamp);
+	if ( speed > maxspeed ) {
+	  maxspeed = speed;
+	  max_speed_tp = VIK_TRACKPOINT(iter->data);
+	}
+      }
+    }
+    iter = iter->next;
+  }
+  
+  if (!max_speed_tp)
+    return NULL;
+
+  return max_speed_tp;
 }
+
+VikTrackpoint* vik_track_get_tp_by_max_alt ( const VikTrack *tr )
+{
+  gdouble maxalt = -5000.0;
+  if ( !tr->trackpoints )
+    return NULL;
+
+  GList *iter = tr->trackpoints;
+  VikTrackpoint *max_alt_tp = NULL;
+
+  while (iter) {
+    if ( VIK_TRACKPOINT(iter->data)->altitude > maxalt ) {
+      maxalt = VIK_TRACKPOINT(iter->data)->altitude;
+      max_alt_tp = VIK_TRACKPOINT(iter->data);
+    }
+    iter = iter->next;
+  }
+
+  if (!max_alt_tp)
+    return NULL;
+
+  return max_alt_tp;
+}
+
+VikTrackpoint* vik_track_get_tp_by_min_alt ( const VikTrack *tr )
+{
+  gdouble minalt = 25000.0;
+  if ( !tr->trackpoints )
+    return NULL;
+
+  GList *iter = tr->trackpoints;
+  VikTrackpoint *min_alt_tp = NULL;
+
+  while (iter) {
+    if ( VIK_TRACKPOINT(iter->data)->altitude < minalt ) {
+      minalt = VIK_TRACKPOINT(iter->data)->altitude;
+      min_alt_tp = VIK_TRACKPOINT(iter->data);
+    }
+    iter = iter->next;
+  }
+
+  if (!min_alt_tp)
+    return NULL;
+
+  return min_alt_tp;
+}
+
+gboolean vik_track_get_minmax_alt ( const VikTrack *tr, gdouble *min_alt, gdouble *max_alt )
+{
+  *min_alt = 25000;
+  *max_alt = -5000;
+  if ( tr && tr->trackpoints && tr->trackpoints->data && (VIK_TRACKPOINT(tr->trackpoints->data)->altitude != VIK_DEFAULT_ALTITUDE) ) {
+    GList *iter = tr->trackpoints->next;
+    gdouble tmp_alt;
+    while (iter)
+    {
+      tmp_alt = VIK_TRACKPOINT(iter->data)->altitude;
+      if ( tmp_alt > *max_alt )
+        *max_alt = tmp_alt;
+      if ( tmp_alt < *min_alt )
+        *min_alt = tmp_alt;
+      iter = iter->next;
+    }
+    return TRUE;
+  }
+  return FALSE;
+}
+
+void vik_track_marshall ( VikTrack *tr, guint8 **data, guint *datalen)
+{
+  GList *tps;
+  GByteArray *b = g_byte_array_new();
+  guint len;
+  guint intp, ntp;
+
+  g_byte_array_append(b, (guint8 *)tr, sizeof(*tr));
+
+  /* we'll fill out number of trackpoints later */
+  intp = b->len;
+  g_byte_array_append(b, (guint8 *)&len, sizeof(len));
+
+  tps = tr->trackpoints;
+  ntp = 0;
+  while (tps) {
+    g_byte_array_append(b, (guint8 *)tps->data, sizeof(VikTrackpoint));
+    tps = tps->next;
+    ntp++;
+  }
+  *(guint *)(b->data + intp) = ntp;
+
+  len = (tr->comment) ? strlen(tr->comment)+1 : 0; 
+  g_byte_array_append(b, (guint8 *)&len, sizeof(len)); 
+  if (tr->comment) g_byte_array_append(b, (guint8 *)tr->comment, len);
+
+  *data = b->data;
+  *datalen = b->len;
+  g_byte_array_free(b, FALSE);
+}
+
+VikTrack *vik_track_unmarshall (guint8 *data, guint datalen)
+{
+  guint len;
+  VikTrack *new_tr = vik_track_new();
+  VikTrackpoint *new_tp;
+  guint ntp;
+  gint i;
+
+  /* only the visibility is needed */
+  new_tr->visible = ((VikTrack *)data)->visible;
+  data += sizeof(*new_tr);
+
+  ntp = *(guint *)data;
+  data += sizeof(ntp);
+
+  for (i=0; i<ntp; i++) {
+    new_tp = vik_trackpoint_new();
+    memcpy(new_tp, data, sizeof(*new_tp));
+    data += sizeof(*new_tp);
+    new_tr->trackpoints = g_list_append(new_tr->trackpoints, new_tp);
+  }
+
+  len = *(guint *)data;
+  data += sizeof(len);
+  if (len) {
+    new_tr->comment = g_strdup((gchar *)data);
+  }
+  return new_tr;
+}
+
+void vik_track_apply_dem_data ( VikTrack *tr )
+{
+  GList *tp_iter;
+  gint16 elev;
+  tp_iter = tr->trackpoints;
+  while ( tp_iter ) {
+    /* TODO: of the 4 possible choices we have for choosing an elevation
+     * (trackpoint in between samples), choose the one with the least elevation change
+     * as the last */
+    elev = a_dems_get_elev_by_coord ( &(VIK_TRACKPOINT(tp_iter->data)->coord), VIK_DEM_INTERPOL_BEST );
+    if ( elev != VIK_DEM_INVALID_ELEVATION )
+      VIK_TRACKPOINT(tp_iter->data)->altitude = elev;
+    tp_iter = tp_iter->next;
+  }
+}
+
+/*
+ * Apply DEM data (if available) - to only the last trackpoint
+ */
+void vik_track_apply_dem_data_last_trackpoint ( VikTrack *tr )
+{
+  gint16 elev;
+  if ( tr->trackpoints ) {
+    /* As in vik_track_apply_dem_data above - use 'best' interpolation method */
+    elev = a_dems_get_elev_by_coord ( &(VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->coord), VIK_DEM_INTERPOL_BEST );
+    if ( elev != VIK_DEM_INVALID_ELEVATION )
+      VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->altitude = elev;
+  }
+}
+
+/* appends t2 to t1, leaving t2 with no trackpoints */
+void vik_track_steal_and_append_trackpoints ( VikTrack *t1, VikTrack *t2 )
+{
+  if ( t1->trackpoints ) {
+    GList *tpiter = t1->trackpoints;
+    while ( tpiter->next )
+      tpiter = tpiter->next;
+    tpiter->next = t2->trackpoints;
+    t2->trackpoints->prev = tpiter;
+  } else
+    t1->trackpoints = t2->trackpoints;
+  t2->trackpoints = NULL;
+}
+
+/* starting at the end, looks backwards for the last "double point", a duplicate trackpoint.
+ * If there is no double point, deletes all the trackpoints.
+ * Returns the new end of the track (or the start if there are no double points)
+ */
+VikCoord *vik_track_cut_back_to_double_point ( VikTrack *tr )
+{
+  GList *iter = tr->trackpoints;
+  VikCoord *rv;
+
+  if ( !iter )
+    return NULL;
+  while ( iter->next )
+    iter = iter->next;
+
+
+  while ( iter->prev ) {
+    if ( vik_coord_equals((VikCoord *)iter->data, (VikCoord *)iter->prev->data) ) {
+      GList *prev = iter->prev;
+
+      rv = g_malloc(sizeof(VikCoord));
+      *rv = *((VikCoord *) iter->data);
+
+      /* truncate trackpoint list */
+      iter->prev = NULL; /* pretend it's the end */
+      g_list_foreach ( iter, (GFunc) g_free, NULL );
+      g_list_free( iter );
+
+      prev->next = NULL;
+
+      return rv;
+    }
+    iter = iter->prev;
+  }
+
+  /* no double point found! */
+  rv = g_malloc(sizeof(VikCoord));
+  *rv = *((VikCoord *) tr->trackpoints->data);
+  g_list_foreach ( tr->trackpoints, (GFunc) g_free, NULL );
+  g_list_free( tr->trackpoints );
+  tr->trackpoints = NULL;
+  return rv;
+}
+