src/viktrack.c

   1 /*
   2  * viking -- GPS Data and Topo Analyzer, Explorer, and Manager
   3  *
   4  * Copyright (C) 2003-2005, Evan Battaglia <gtoevan@gmx.net>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  *
  20  */
  21 #ifdef HAVE_CONFIG_H
  22 #include "config.h"
  23 #endif
  24
  25 #include <glib.h>
  26 #include <time.h>
  27 #include <stdlib.h>
  28 #ifdef HAVE_STRING_H
  29 #include <string.h>
  30 #endif
  31 #ifdef HAVE_MATH_H
  32 #include <math.h>
  33 #endif
  34
  35 #include "coords.h"
  36 #include "vikcoord.h"
  37 #include "viktrack.h"
  38 #include "globals.h"
  39 #include "dems.h"
  40
  41 VikTrack *vik_track_new()
  42 {
  43   VikTrack *tr = g_malloc0 ( sizeof ( VikTrack ) );
  44   tr->ref_count = 1;
  45   return tr;
  46 }
  47
  48 void vik_track_set_comment_no_copy(VikTrack *tr, gchar *comment)
  49 {
  50   if ( tr->comment )
  51     g_free ( tr->comment );
  52   tr->comment = comment;
  53 }
  54
  55
  56 void vik_track_set_comment(VikTrack *tr, const gchar *comment)
  57 {
  58   if ( tr->comment )
  59     g_free ( tr->comment );
  60
  61   if ( comment && comment[0] != '\0' )
  62     tr->comment = g_strdup(comment);
  63   else
  64     tr->comment = NULL;
  65 }
  66
  67 void vik_track_ref(VikTrack *tr)
  68 {
  69   tr->ref_count++;
  70 }
  71
  72 void vik_track_set_property_dialog(VikTrack *tr, GtkWidget *dialog)
  73 {
  74   /* Warning: does not check for existing dialog */
  75   tr->property_dialog = dialog;
  76 }
  77
  78 void vik_track_clear_property_dialog(VikTrack *tr)
  79 {
  80   tr->property_dialog = NULL;
  81 }
  82
  83 void vik_track_free(VikTrack *tr)
  84 {
  85   if ( tr->ref_count-- > 1 )
  86     return;
  87
  88   if ( tr->comment )
  89     g_free ( tr->comment );
  90   g_list_foreach ( tr->trackpoints, (GFunc) g_free, NULL );
  91   g_list_free( tr->trackpoints );
  92   if (tr->property_dialog)
  93     gtk_widget_destroy ( GTK_WIDGET(tr->property_dialog) );
  94   g_free ( tr );
  95 }
  96
  97 VikTrack *vik_track_copy ( const VikTrack *tr )
  98 {
  99   VikTrack *new_tr = vik_track_new();
 100   VikTrackpoint *new_tp;
 101   GList *tp_iter = tr->trackpoints;
 102   new_tr->visible = tr->visible;
 103   new_tr->trackpoints = NULL;
 104   while ( tp_iter )
 105   {
 106     new_tp = g_malloc ( sizeof ( VikTrackpoint ) );
 107     *new_tp = *((VikTrackpoint *)(tp_iter->data));
 108     new_tr->trackpoints = g_list_append ( new_tr->trackpoints, new_tp );
 109     tp_iter = tp_iter->next;
 110   }
 111   vik_track_set_comment(new_tr,tr->comment);
 112   return new_tr;
 113 }
 114
 115 VikTrackpoint *vik_trackpoint_new()
 116 {
 117   VikTrackpoint *tp = g_malloc0(sizeof(VikTrackpoint));
 118   tp->speed = NAN;
 119   tp->course = NAN;
 120   tp->altitude = VIK_DEFAULT_ALTITUDE;
 121   tp->hdop = VIK_DEFAULT_DOP;
 122   tp->vdop = VIK_DEFAULT_DOP;
 123   tp->pdop = VIK_DEFAULT_DOP;
 124   return tp;
 125 }
 126
 127 void vik_trackpoint_free(VikTrackpoint *tp)
 128 {
 129   g_free(tp);
 130 }
 131
 132 VikTrackpoint *vik_trackpoint_copy(VikTrackpoint *tp)
 133 {
 134   VikTrackpoint *rv = vik_trackpoint_new();
 135   *rv = *tp;
 136   return rv;
 137 }
 138
 139 gdouble vik_track_get_length(const VikTrack *tr)
 140 {
 141   gdouble len = 0.0;
 142   if ( tr->trackpoints )
 143   {
 144     GList *iter = tr->trackpoints->next;
 145     while (iter)
 146     {
 147       if ( ! VIK_TRACKPOINT(iter->data)->newsegment )
 148         len += vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 149                                 &(VIK_TRACKPOINT(iter->prev->data)->coord) );
 150       iter = iter->next;
 151     }
 152   }
 153   return len;
 154 }
 155
 156 gdouble vik_track_get_length_including_gaps(const VikTrack *tr)
 157 {
 158   gdouble len = 0.0;
 159   if ( tr->trackpoints )
 160   {
 161     GList *iter = tr->trackpoints->next;
 162     while (iter)
 163     {
 164       len += vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 165                               &(VIK_TRACKPOINT(iter->prev->data)->coord) );
 166       iter = iter->next;
 167     }
 168   }
 169   return len;
 170 }
 171
 172 gulong vik_track_get_tp_count(const VikTrack *tr)
 173 {
 174   gulong num = 0;
 175   GList *iter = tr->trackpoints;
 176   while ( iter )
 177   {
 178     num++;
 179     iter = iter->next;
 180   }
 181   return num;
 182 }
 183
 184 gulong vik_track_get_dup_point_count ( const VikTrack *tr )
 185 {
 186   gulong num = 0;
 187   GList *iter = tr->trackpoints;
 188   while ( iter )
 189   {
 190     if ( iter->next && vik_coord_equals ( &(VIK_TRACKPOINT(iter->data)->coord),
 191                        &(VIK_TRACKPOINT(iter->next->data)->coord) ) )
 192       num++;
 193     iter = iter->next;
 194   }
 195   return num;
 196 }
 197
 198 void vik_track_remove_dup_points ( VikTrack *tr )
 199 {
 200   GList *iter = tr->trackpoints;
 201   while ( iter )
 202   {
 203     if ( iter->next && vik_coord_equals ( &(VIK_TRACKPOINT(iter->data)->coord),
 204                        &(VIK_TRACKPOINT(iter->next->data)->coord) ) )
 205     {
 206       g_free ( iter->next->data );
 207       tr->trackpoints = g_list_delete_link ( tr->trackpoints, iter->next );
 208     }
 209     else
 210       iter = iter->next;
 211   }
 212 }
 213
 214 guint vik_track_get_segment_count(const VikTrack *tr)
 215 {
 216   guint num = 1;
 217   GList *iter = tr->trackpoints;
 218   if ( !iter )
 219     return 0;
 220   while ( (iter = iter->next) )
 221   {
 222     if ( VIK_TRACKPOINT(iter->data)->newsegment )
 223       num++;
 224   }
 225   return num;
 226 }
 227
 228 VikTrack **vik_track_split_into_segments(VikTrack *t, guint *ret_len)
 229 {
 230   VikTrack **rv;
 231   VikTrack *tr;
 232   guint i;
 233   guint segs = vik_track_get_segment_count(t);
 234   GList *iter;
 235
 236   if ( segs < 2 )
 237   {
 238     *ret_len = 0;
 239     return NULL;
 240   }
 241
 242   rv = g_malloc ( segs * sizeof(VikTrack *) );
 243   tr = vik_track_copy ( t );
 244   rv[0] = tr;
 245   iter = tr->trackpoints;
 246
 247   i = 1;
 248   while ( (iter = iter->next) )
 249   {
 250     if ( VIK_TRACKPOINT(iter->data)->newsegment )
 251     {
 252       iter->prev->next = NULL;
 253       iter->prev = NULL;
 254       rv[i] = vik_track_new();
 255       if ( tr->comment )
 256         vik_track_set_comment ( rv[i], tr->comment );
 257       rv[i]->visible = tr->visible;
 258       rv[i]->trackpoints = iter;
 259       i++;
 260     }
 261   }
 262   *ret_len = segs;
 263   return rv;
 264 }
 265
 266 void vik_track_reverse ( VikTrack *tr )
 267 {
 268   GList *iter;
 269   tr->trackpoints = g_list_reverse(tr->trackpoints);
 270
 271   /* fix 'newsegment' */
 272   iter = g_list_last ( tr->trackpoints );
 273   while ( iter )
 274   {
 275     if ( ! iter->next ) /* last segment, was first, cancel newsegment. */
 276       VIK_TRACKPOINT(iter->data)->newsegment = FALSE;
 277     if ( ! iter->prev ) /* first segment by convention has newsegment flag. */
 278       VIK_TRACKPOINT(iter->data)->newsegment = TRUE;
 279     else if ( VIK_TRACKPOINT(iter->data)->newsegment && iter->next )
 280     {
 281       VIK_TRACKPOINT(iter->next->data)->newsegment = TRUE;
 282       VIK_TRACKPOINT(iter->data)->newsegment = FALSE;
 283     }
 284     iter = iter->prev;
 285   }
 286 }
 287
 288 gdouble vik_track_get_average_speed(const VikTrack *tr)
 289 {
 290   gdouble len = 0.0;
 291   guint32 time = 0;
 292   if ( tr->trackpoints )
 293   {
 294     GList *iter = tr->trackpoints->next;
 295     while (iter)
 296     {
 297       if ( VIK_TRACKPOINT(iter->data)->has_timestamp &&
 298           VIK_TRACKPOINT(iter->prev->data)->has_timestamp &&
 299           (! VIK_TRACKPOINT(iter->data)->newsegment) )
 300       {
 301         len += vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 302                                 &(VIK_TRACKPOINT(iter->prev->data)->coord) );
 303         time += ABS(VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(iter->prev->data)->timestamp);
 304       }
 305       iter = iter->next;
 306     }
 307   }
 308   return (time == 0) ? 0 : ABS(len/time);
 309 }
 310
 311 gdouble vik_track_get_max_speed(const VikTrack *tr)
 312 {
 313   gdouble maxspeed = 0.0, speed = 0.0;
 314   if ( tr->trackpoints )
 315   {
 316     GList *iter = tr->trackpoints->next;
 317     while (iter)
 318     {
 319       if ( VIK_TRACKPOINT(iter->data)->has_timestamp &&
 320           VIK_TRACKPOINT(iter->prev->data)->has_timestamp &&
 321           (! VIK_TRACKPOINT(iter->data)->newsegment) )
 322       {
 323         speed =  vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord), &(VIK_TRACKPOINT(iter->prev->data)->coord) )
 324                  / ABS(VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(iter->prev->data)->timestamp);
 325         if ( speed > maxspeed )
 326           maxspeed = speed;
 327       }
 328       iter = iter->next;
 329     }
 330   }
 331   return maxspeed;
 332 }
 333
 334 void vik_track_convert ( VikTrack *tr, VikCoordMode dest_mode )
 335 {
 336   GList *iter = tr->trackpoints;
 337   while (iter)
 338   {
 339     vik_coord_convert ( &(VIK_TRACKPOINT(iter->data)->coord), dest_mode );
 340     iter = iter->next;
 341   }
 342 }
 343
 344 /* I understood this when I wrote it ... maybe ... Basically it eats up the
 345  * proper amounts of length on the track and averages elevation over that. */
 346 gdouble *vik_track_make_elevation_map ( const VikTrack *tr, guint16 num_chunks )
 347 {
 348   gdouble *pts;
 349   gdouble total_length, chunk_length, current_dist, current_area_under_curve, current_seg_length, dist_along_seg = 0.0;
 350   gdouble altitude1, altitude2;
 351   guint16 current_chunk;
 352   gboolean ignore_it = FALSE;
 353
 354   GList *iter = tr->trackpoints;
 355
 356   if (!iter || !iter->next) /* zero- or one-point track */
 357           return NULL;
 358
 359   { /* test if there's anything worth calculating */
 360     gboolean okay = FALSE;
 361     while ( iter )
 362     {
 363       if ( VIK_TRACKPOINT(iter->data)->altitude != VIK_DEFAULT_ALTITUDE ) {
 364         okay = TRUE; break;
 365       }
 366       iter = iter->next;
 367     }
 368     if ( ! okay )
 369       return NULL;
 370   }
 371
 372   iter = tr->trackpoints;
 373
 374   g_assert ( num_chunks < 16000 );
 375
 376   pts = g_malloc ( sizeof(gdouble) * num_chunks );
 377
 378   total_length = vik_track_get_length_including_gaps ( tr );
 379   chunk_length = total_length / num_chunks;
 380
 381   /* Zero chunk_length (eg, track of 2 tp with the same loc) will cause crash */
 382   if (chunk_length <= 0) {
 383     g_free(pts);
 384     return NULL;
 385   }
 386
 387   current_dist = 0.0;
 388   current_area_under_curve = 0;
 389   current_chunk = 0;
 390   current_seg_length = 0;
 391
 392   current_seg_length = vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 393       &(VIK_TRACKPOINT(iter->next->data)->coord) );
 394   altitude1 = VIK_TRACKPOINT(iter->data)->altitude;
 395   altitude2 = VIK_TRACKPOINT(iter->next->data)->altitude;
 396   dist_along_seg = 0;
 397
 398   while ( current_chunk < num_chunks ) {
 399
 400     /* go along current seg */
 401     if ( current_seg_length && (current_seg_length - dist_along_seg) > chunk_length ) {
 402       dist_along_seg += chunk_length;
 403
 404       /*        /
 405        *   pt2 *
 406        *      /x       altitude = alt_at_pt_1 + alt_at_pt_2 / 2 = altitude1 + slope * dist_value_of_pt_inbetween_pt1_and_pt2
 407        *     /xx   avg altitude = area under curve / chunk len
 408        *pt1 *xxx   avg altitude = altitude1 + (altitude2-altitude1)/(current_seg_length)*(dist_along_seg + (chunk_len/2))
 409        *   / xxx
 410        *  /  xxx
 411        **/
 412
 413       if ( ignore_it )
 414         pts[current_chunk] = VIK_DEFAULT_ALTITUDE;
 415       else
 416         pts[current_chunk] = altitude1 + (altitude2-altitude1)*((dist_along_seg - (chunk_length/2))/current_seg_length);
 417
 418       current_chunk++;
 419     } else {
 420       /* finish current seg */
 421       if ( current_seg_length ) {
 422         gdouble altitude_at_dist_along_seg = altitude1 + (altitude2-altitude1)/(current_seg_length)*dist_along_seg;
 423         current_dist = current_seg_length - dist_along_seg;
 424         current_area_under_curve = current_dist*(altitude_at_dist_along_seg + altitude2)*0.5;
 425       } else { current_dist = current_area_under_curve = 0; } /* should only happen if first current_seg_length == 0 */
 426
 427       /* get intervening segs */
 428       iter = iter->next;
 429       while ( iter && iter->next ) {
 430         current_seg_length = vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 431             &(VIK_TRACKPOINT(iter->next->data)->coord) );
 432         altitude1 = VIK_TRACKPOINT(iter->data)->altitude;
 433         altitude2 = VIK_TRACKPOINT(iter->next->data)->altitude;
 434         ignore_it = VIK_TRACKPOINT(iter->next->data)->newsegment;
 435
 436         if ( chunk_length - current_dist >= current_seg_length ) {
 437           current_dist += current_seg_length;
 438           current_area_under_curve += current_seg_length * (altitude1+altitude2) * 0.5;
 439           iter = iter->next;
 440         } else {
 441           break;
 442         }
 443       }
 444
 445       /* final seg */
 446       dist_along_seg = chunk_length - current_dist;
 447       if ( ignore_it || !iter->next ) {
 448         pts[current_chunk] = current_area_under_curve / current_dist;
 449         if (!iter->next) {
 450           int i;
 451           for (i = current_chunk + 1; i < num_chunks; i++)
 452             pts[i] = pts[current_chunk];
 453           break;
 454         }
 455       }
 456       else {
 457         current_area_under_curve += dist_along_seg * (altitude1 + (altitude2 - altitude1)*dist_along_seg/current_seg_length);
 458         pts[current_chunk] = current_area_under_curve / chunk_length;
 459       }
 460
 461       current_dist = 0;
 462       current_chunk++;
 463     }
 464   }
 465
 466   return pts;
 467 }
 468
 469
 470 void vik_track_get_total_elevation_gain(const VikTrack *tr, gdouble *up, gdouble *down)
 471 {
 472   gdouble diff;
 473   *up = *down = 0;
 474   if ( tr->trackpoints && VIK_TRACKPOINT(tr->trackpoints->data)->altitude != VIK_DEFAULT_ALTITUDE )
 475   {
 476     GList *iter = tr->trackpoints->next;
 477     while (iter)
 478     {
 479       diff = VIK_TRACKPOINT(iter->data)->altitude - VIK_TRACKPOINT(iter->prev->data)->altitude;
 480       if ( diff > 0 )
 481         *up += diff;
 482       else
 483         *down -= diff;
 484       iter = iter->next;
 485     }
 486   } else
 487     *up = *down = VIK_DEFAULT_ALTITUDE;
 488 }
 489
 490
 491 /* by Alex Foobarian */
 492 gdouble *vik_track_make_speed_map ( const VikTrack *tr, guint16 num_chunks )
 493 {
 494   gdouble *v, *s, *t;
 495   gdouble duration, chunk_dur;
 496   time_t t1, t2;
 497   int i, pt_count, numpts, index;
 498   GList *iter;
 499
 500   if ( ! tr->trackpoints )
 501     return NULL;
 502
 503   g_assert ( num_chunks < 16000 );
 504
 505   t1 = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
 506   t2 = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
 507   duration = t2 - t1;
 508
 509   if ( !t1 || !t2 || !duration )
 510     return NULL;
 511
 512   if (duration < 0) {
 513     g_warning("negative duration: unsorted trackpoint timestamps?");
 514     return NULL;
 515   }
 516   pt_count = vik_track_get_tp_count(tr);
 517
 518   v = g_malloc ( sizeof(gdouble) * num_chunks );
 519   chunk_dur = duration / num_chunks;
 520
 521   s = g_malloc(sizeof(double) * pt_count);
 522   t = g_malloc(sizeof(double) * pt_count);
 523
 524   iter = tr->trackpoints->next;
 525   numpts = 0;
 526   s[0] = 0;
 527   t[0] = VIK_TRACKPOINT(iter->prev->data)->timestamp;
 528   numpts++;
 529   while (iter) {
 530     s[numpts] = s[numpts-1] + vik_coord_diff ( &(VIK_TRACKPOINT(iter->prev->data)->coord), &(VIK_TRACKPOINT(iter->data)->coord) );
 531     t[numpts] = VIK_TRACKPOINT(iter->data)->timestamp;
 532     numpts++;
 533     iter = iter->next;
 534   }
 535
 536   /* In the following computation, we iterate through periods of time of duration chunk_dur.
 537    * The first period begins at the beginning of the track.  The last period ends at the end of the track.
 538    */
 539   index = 0; /* index of the current trackpoint. */
 540   for (i = 0; i < num_chunks; i++) {
 541     /* we are now covering the interval from t[0] + i*chunk_dur to t[0] + (i+1)*chunk_dur.
 542      * find the first trackpoint outside the current interval, averaging the speeds between intermediate trackpoints.
 543      */
 544     if (t[0] + i*chunk_dur >= t[index]) {
 545       gdouble acc_t = 0, acc_s = 0;
 546       numpts = 0;
 547       while (t[0] + i*chunk_dur >= t[index]) {
 548         acc_s += (s[index+1]-s[index]);
 549         acc_t += (t[index+1]-t[index]);
 550         index++;
 551         numpts++;
 552       }
 553       v[i] = acc_s/acc_t;
 554     }
 555     else if (i) {
 556       v[i] = v[i-1];
 557     }
 558     else {
 559       v[i] = 0;
 560     }
 561   }
 562   g_free(s);
 563   g_free(t);
 564   return v;
 565 }
 566
 567 /* by Alex Foobarian */
 568 VikTrackpoint *vik_track_get_closest_tp_by_percentage_dist ( VikTrack *tr, gdouble reldist, gdouble *meters_from_start )
 569 {
 570   gdouble dist = vik_track_get_length_including_gaps(tr) * reldist;
 571   gdouble current_dist = 0.0;
 572   gdouble current_inc = 0.0;
 573   if ( tr->trackpoints )
 574   {
 575     GList *iter = tr->trackpoints->next;
 576     GList *last_iter = NULL;
 577     gdouble last_dist = 0.0;
 578     while (iter)
 579     {
 580       current_inc = vik_coord_diff ( &(VIK_TRACKPOINT(iter->data)->coord),
 581                                      &(VIK_TRACKPOINT(iter->prev->data)->coord) );
 582       last_dist = current_dist;
 583       current_dist += current_inc;
 584       if ( current_dist >= dist )
 585         break;
 586       last_iter = iter;
 587       iter = iter->next;
 588     }
 589     if (!iter) { /* passing the end the track */
 590       if (last_iter) {
 591         if (meters_from_start)
 592           *meters_from_start = last_dist;
 593         return(VIK_TRACKPOINT(last_iter->data));
 594       }
 595       else
 596         return NULL;
 597     }
 598     /* we've gone past the dist already, was prev trackpoint closer? */
 599     /* should do a vik_coord_average_weighted() thingy. */
 600     if ( iter->prev && abs(current_dist-current_inc-dist) < abs(current_dist-dist) ) {
 601       if (meters_from_start)
 602         *meters_from_start = last_dist;
 603       iter = iter->prev;
 604     }
 605     else
 606       if (meters_from_start)
 607         *meters_from_start = current_dist;
 608
 609     return VIK_TRACKPOINT(iter->data);
 610
 611   }
 612   return NULL;
 613 }
 614
 615 VikTrackpoint *vik_track_get_closest_tp_by_percentage_time ( VikTrack *tr, gdouble reltime, time_t *seconds_from_start )
 616 {
 617   time_t t_pos, t_start, t_end, t_total;
 618   t_start = VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
 619   t_end = VIK_TRACKPOINT(g_list_last(tr->trackpoints)->data)->timestamp;
 620   t_total = t_end - t_start;
 621
 622   t_pos = t_start + t_total * reltime;
 623
 624   if ( !tr->trackpoints )
 625     return NULL;
 626
 627   GList *iter = tr->trackpoints;
 628
 629   while (iter) {
 630     if (VIK_TRACKPOINT(iter->data)->timestamp == t_pos)
 631       break;
 632     if (VIK_TRACKPOINT(iter->data)->timestamp > t_pos) {
 633       if (iter->prev == NULL)  /* first trackpoint */
 634         break;
 635       time_t t_before = t_pos - VIK_TRACKPOINT(iter->prev)->timestamp;
 636       time_t t_after = VIK_TRACKPOINT(iter->data)->timestamp - t_pos;
 637       if (t_before <= t_after)
 638         iter = iter->prev;
 639       break;
 640     }
 641     else if ((iter->next == NULL) && (t_pos < (VIK_TRACKPOINT(iter->data)->timestamp + 3))) /* last trackpoint: accommodate for round-off */
 642       break;
 643     iter = iter->next;
 644   }
 645
 646   if (!iter)
 647     return NULL;
 648   if (seconds_from_start)
 649     *seconds_from_start = VIK_TRACKPOINT(iter->data)->timestamp - VIK_TRACKPOINT(tr->trackpoints->data)->timestamp;
 650   return VIK_TRACKPOINT(iter->data);
 651 }
 652
 653 gboolean vik_track_get_minmax_alt ( const VikTrack *tr, gdouble *min_alt, gdouble *max_alt )
 654 {
 655   *min_alt = 25000;
 656   *max_alt = -5000;
 657   if ( tr && tr->trackpoints && tr->trackpoints->data && (VIK_TRACKPOINT(tr->trackpoints->data)->altitude != VIK_DEFAULT_ALTITUDE) ) {
 658     GList *iter = tr->trackpoints->next;
 659     gdouble tmp_alt;
 660     while (iter)
 661     {
 662       tmp_alt = VIK_TRACKPOINT(iter->data)->altitude;
 663       if ( tmp_alt > *max_alt )
 664         *max_alt = tmp_alt;
 665       if ( tmp_alt < *min_alt )
 666         *min_alt = tmp_alt;
 667       iter = iter->next;
 668     }
 669     return TRUE;
 670   }
 671   return FALSE;
 672 }
 673
 674 void vik_track_marshall ( VikTrack *tr, guint8 **data, guint *datalen)
 675 {
 676   GList *tps;
 677   GByteArray *b = g_byte_array_new();
 678   guint len;
 679   guint intp, ntp;
 680
 681   g_byte_array_append(b, (guint8 *)tr, sizeof(*tr));
 682
 683   /* we'll fill out number of trackpoints later */
 684   intp = b->len;
 685   g_byte_array_append(b, (guint8 *)&len, sizeof(len));
 686
 687   tps = tr->trackpoints;
 688   ntp = 0;
 689   while (tps) {
 690     g_byte_array_append(b, (guint8 *)tps->data, sizeof(VikTrackpoint));
 691     tps = tps->next;
 692     ntp++;
 693   }
 694   *(guint *)(b->data + intp) = ntp;
 695
 696   len = (tr->comment) ? strlen(tr->comment)+1 : 0;
 697   g_byte_array_append(b, (guint8 *)&len, sizeof(len));
 698   if (tr->comment) g_byte_array_append(b, (guint8 *)tr->comment, len);
 699
 700   *data = b->data;
 701   *datalen = b->len;
 702   g_byte_array_free(b, FALSE);
 703 }
 704
 705 VikTrack *vik_track_unmarshall (guint8 *data, guint datalen)
 706 {
 707   guint len;
 708   VikTrack *new_tr = vik_track_new();
 709   VikTrackpoint *new_tp;
 710   guint ntp;
 711   gint i;
 712
 713   /* only the visibility is needed */
 714   new_tr->visible = ((VikTrack *)data)->visible;
 715   data += sizeof(*new_tr);
 716
 717   ntp = *(guint *)data;
 718   data += sizeof(ntp);
 719
 720   for (i=0; i<ntp; i++) {
 721     new_tp = vik_trackpoint_new();
 722     memcpy(new_tp, data, sizeof(*new_tp));
 723     data += sizeof(*new_tp);
 724     new_tr->trackpoints = g_list_append(new_tr->trackpoints, new_tp);
 725   }
 726
 727   len = *(guint *)data;
 728   data += sizeof(len);
 729   if (len) {
 730     new_tr->comment = g_strdup((gchar *)data);
 731   }
 732   return new_tr;
 733 }
 734
 735 void vik_track_apply_dem_data ( VikTrack *tr )
 736 {
 737   GList *tp_iter;
 738   gint16 elev;
 739   tp_iter = tr->trackpoints;
 740   while ( tp_iter ) {
 741     /* TODO: of the 4 possible choices we have for choosing an elevation
 742      * (trackpoint in between samples), choose the one with the least elevation change
 743      * as the last */
 744     elev = a_dems_get_elev_by_coord ( &(VIK_TRACKPOINT(tp_iter->data)->coord), VIK_DEM_INTERPOL_BEST );
 745     if ( elev != VIK_DEM_INVALID_ELEVATION )
 746       VIK_TRACKPOINT(tp_iter->data)->altitude = elev;
 747     tp_iter = tp_iter->next;
 748   }
 749 }
 750
 751 /* appends t2 to t1, leaving t2 with no trackpoints */
 752 void vik_track_steal_and_append_trackpoints ( VikTrack *t1, VikTrack *t2 )
 753 {
 754   if ( t1->trackpoints ) {
 755     GList *tpiter = t1->trackpoints;
 756     while ( tpiter->next )
 757       tpiter = tpiter->next;
 758     tpiter->next = t2->trackpoints;
 759     t2->trackpoints->prev = tpiter;
 760   } else
 761     t1->trackpoints = t2->trackpoints;
 762   t2->trackpoints = NULL;
 763 }
 764
 765 /* starting at the end, looks backwards for the last "double point", a duplicate trackpoint.
 766  * this is indicative of magic scissors continued use. If there is no double point,
 767  * deletes all the trackpoints. Returns the new end of the track (or the start if
 768  * there are no double points
 769  */
 770 VikCoord *vik_track_cut_back_to_double_point ( VikTrack *tr )
 771 {
 772   GList *iter = tr->trackpoints;
 773   VikCoord *rv;
 774
 775   if ( !iter )
 776     return NULL;
 777   while ( iter->next )
 778     iter = iter->next;
 779
 780
 781   while ( iter->prev ) {
 782     if ( vik_coord_equals((VikCoord *)iter->data, (VikCoord *)iter->prev->data) ) {
 783       GList *prev = iter->prev;
 784
 785       rv = g_malloc(sizeof(VikCoord));
 786       *rv = *((VikCoord *) iter->data);
 787
 788       /* truncate trackpoint list */
 789       iter->prev = NULL; /* pretend it's the end */
 790       g_list_foreach ( iter, (GFunc) g_free, NULL );
 791       g_list_free( iter );
 792
 793       prev->next = NULL;
 794
 795       return rv;
 796     }
 797     iter = iter->prev;
 798   }
 799
 800   /* no double point found! */
 801   rv = g_malloc(sizeof(VikCoord));
 802   *rv = *((VikCoord *) tr->trackpoints->data);
 803   g_list_foreach ( tr->trackpoints, (GFunc) g_free, NULL );
 804   g_list_free( tr->trackpoints );
 805   tr->trackpoints = NULL;
 806   return rv;
 807 }
 808