source: git/src/netskel.c @ c20d521

/* netskel.c
 * Survex network reduction - remove trailing traverses and concatenate
 * traverses between junctions
 * Copyright (C) 1991-2004,2005,2006,2010,2011,2012,2013,2014 Olly Betts
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

/* #define BLUNDER_DETECTION */

#if 0
#define DEBUG_INVALID 1
#define VALIDATE 1
#define DUMP_NETWORK 1
#endif

#ifdef HAVE_CONFIG_H
# include <config.h>
#endif

#include "validate.h"
#include "debug.h"
#include "cavern.h"
#include "filename.h"
#include "message.h"
#include "filelist.h"
#include "img_hosted.h"
#include "netartic.h"
#include "netbits.h"
#include "netskel.h"
#include "network.h"
#include "out.h"

#define sqrdd(X) (sqrd((X)[0]) + sqrd((X)[1]) + sqrd((X)[2]))

typedef struct Stack {
   struct Link *join1, *join2;
   struct Stack *next;
} stack;

typedef struct StackTr {
   struct Link *join1;
   struct StackTr *next;
} stackTrail;

/* string used between things in traverse printouts eg \1 - \2 - \3 -...*/
static const char *szLink = " - ";
static const char *szLinkEq = " = "; /* use this one for equates */

#if 0
#define fprint_prefix(FH, NAME) BLK((fprint_prefix)((FH), (NAME));\
                                    fprintf((FH), " [%p]", (void*)(NAME)); )
#endif

static stack *ptr; /* Ptr to TRaverse linked list for in-between travs */
static stackTrail *ptrTrail; /* Ptr to TRaverse linked list for trail travs*/

static void remove_trailing_travs(void);
static void remove_travs(void);
static void replace_travs(void);
static void replace_trailing_travs(void);
static void write_passage_models(void);

static void concatenate_trav(node *stn, int i);

static void err_stat(int cLegsTrav, double lenTrav,
                     double eTot, double eTotTheo,
                     double hTot, double hTotTheo,
                     double vTot, double vTotTheo);

extern void
solve_network(void /*node *stnlist*/)
{
   static int first_solve = 1;
   node *stn;

   if (stnlist == NULL) {
      if (first_solve) fatalerror(/*No survey data*/43);
      /* We've had a *solve followed by another *solve (or the implicit
       * *solve at the end of the data.  Don't moan about that. */
      return;
   }
   ptr = NULL;
   ptrTrail = NULL;
   dump_network();

   /* If there are no fixed points, invent one.  Do this first to
    * avoid problems with sub-nodes of the invented fix which have
    * been removed.  It also means we can fix the "first" station,
    * which makes more sense to the user. */
   FOR_EACH_STN(stn, stnlist)
      if (fixed(stn)) break;

   if (!stn && first_solve) {
     /* If we've had a *solve and all the new survey since then is hanging,
      * we don't want to invent a fixed point.  We want to complain but
      * the easiest way to is just to continue processing and let
      * articulate() catch this condition as it will any hanging survey
      * data. */
      node *stnFirst = NULL;

      /* New stations are pushed onto the head of the list, so the
       * first station added is the last in the list. */
      FOR_EACH_STN(stn, stnlist) {
          /* Prefer a station with legs attached when choosing one to fix
           * so that if there's a hanging station on a nosurvey leg we pick
           * the main clump of survey data. */
          if (stnFirst && !stnFirst->leg[0]) continue;
          stnFirst = stn;
      }

      /* If we've got nosurvey legs, then the station we find to fix could have
       * no real legs attached. */
      SVX_ASSERT2(nosurveyhead || stnFirst->leg[0], "no fixed stns, but we've got a zero node!");
      SVX_ASSERT2(stnFirst, "no stations left in net!");
      stn = stnFirst;
      printf(msg(/*Survey has no fixed points. Therefore I’ve fixed %s at (0,0,0)*/72),
             sprint_prefix(stn->name));
      putnl();
      POS(stn,0) = (real)0.0;
      POS(stn,1) = (real)0.0;
      POS(stn,2) = (real)0.0;
      fix(stn);
   }

   first_solve = 0;

   remove_trailing_travs();
   validate(); dump_network();
   remove_travs();
   validate(); dump_network();
   remove_subnets();
   validate(); dump_network();
   articulate();
   validate(); dump_network();
   replace_subnets();
   validate(); dump_network();
   replace_travs();
   validate(); dump_network();
   replace_trailing_travs();
   validate(); dump_network();

   /* Now write out any passage models. */
   write_passage_models();
}

static void
remove_trailing_travs(void)
{
   node *stn;
   out_current_action(msg(/*Removing trailing traverses*/125));
   FOR_EACH_STN(stn, stnlist) {
      if (!fixed(stn) && one_node(stn)) {
         int i = 0;
         int j;
         node *stn2 = stn;
         stackTrail *trav;

#if PRINT_NETBITS
         printf("Removed trailing trav ");
#endif
         do {
            struct Link *leg;
#if PRINT_NETBITS
            print_prefix(stn2->name); printf("<%p>",stn2); fputs(szLink, stdout);
#endif
            remove_stn_from_list(&stnlist, stn2);
            leg = stn2->leg[i];
            j = reverse_leg_dirn(leg);
            stn2 = leg->l.to;
            i = j ^ 1; /* flip direction for other leg of 2 node */
            /* stop if fixed or 3 or 1 node */
         } while (two_node(stn2) && !fixed(stn2));

         /* put traverse on stack */
         trav = osnew(stackTrail);
         trav->join1 = stn2->leg[j];
         trav->next = ptrTrail;
         ptrTrail = trav;

         /* We want to keep all 2-nodes using legs 0 and 1 and all one nodes
          * using leg 0 so we may need to swap leg j with leg 2 (for a 3 node)
          * or leg 1 (for a fixed 2 node) */
         if ((j == 0 && !one_node(stn2)) || (j == 1 && three_node(stn2))) {
            /* i is the direction to swap with */
            i = (three_node(stn2)) ? 2 : 1;
            /* change the other direction of leg i to use leg j */
            reverse_leg(stn2->leg[i])->l.reverse += j - i;
            stn2->leg[j] = stn2->leg[i];
            j = i;
         }
         stn2->leg[j] = NULL;

#if PRINT_NETBITS
         print_prefix(stn2->name); printf("<%p>",stn2); putnl();
#endif
      }
   }
}

static void
remove_travs(void)
{
   node *stn;
   out_current_action(msg(/*Concatenating traverses*/126));
   FOR_EACH_STN(stn, stnlist) {
      if (fixed(stn) || three_node(stn)) {
         int d;
         for (d = 0; d <= 2; d++) {
            linkfor *leg = stn->leg[d];
            if (leg && !(leg->l.reverse & FLAG_REPLACEMENTLEG))
               concatenate_trav(stn, d);
         }
      }
   }
}

static void
concatenate_trav(node *stn, int i)
{
   int j;
   stack *trav;
   node *stn2;
   linkfor *newleg, *newleg2;

   stn2 = stn->leg[i]->l.to;
   /* Reject single legs as they may be already concatenated traverses */
   if (fixed(stn2) || !two_node(stn2)) return;

   trav = osnew(stack);
   newleg2 = (linkfor*)osnew(linkrev);

#if PRINT_NETBITS
   printf("Concatenating trav "); print_prefix(stn->name); printf("<%p>",stn);
#endif

   newleg2->l.to = stn;
   newleg2->l.reverse = i | FLAG_REPLACEMENTLEG;
   trav->join1 = stn->leg[i];

   j = reverse_leg_dirn(stn->leg[i]);
   SVX_ASSERT(j == 0 || j == 1);

   newleg = copy_link(stn->leg[i]);

   while (1) {
      stn = stn2;

#if PRINT_NETBITS
      fputs(szLink, stdout); print_prefix(stn->name); printf("<%p>",stn);
#endif

      /* stop if fixed or 3 or 1 node */
      if (fixed(stn) || !two_node(stn)) break;

      remove_stn_from_list(&stnlist, stn);

      i = j ^ 1; /* flip direction for other leg of 2 node */

      stn2 = stn->leg[i]->l.to;
      j = reverse_leg_dirn(stn->leg[i]);

      addto_link(newleg, stn->leg[i]);
   }

   trav->join2 = stn->leg[j];
   trav->next = ptr;
   ptr = trav;

   newleg->l.to = stn;
   newleg->l.reverse = j | FLAG_DATAHERE | FLAG_REPLACEMENTLEG;

   newleg2->l.to->leg[reverse_leg_dirn(newleg2)] = newleg;
   /* i.e. stn->leg[i] = newleg; with original stn and i */

   stn->leg[j] = newleg2;

#if PRINT_NETBITS
   putchar(' ');
   print_var(&(newleg->v));
   printf("\nStacked ");
   print_prefix(newleg2->l.to->name);
   printf(",%d-", reverse_leg_dirn(newleg2));
   print_prefix(stn->name);
   printf(",%d\n", j);
#endif
}

#ifdef BLUNDER_DETECTION
/* expected_error is actually squared... */
/* only called if fhErrStat != NULL */
static void
do_gross(delta e, delta v, node *stn1, node *stn2, double expected_error)
{
   double hsqrd, rsqrd, s, cx, cy, cz;
   double tot;
   int i;
   int output = 0;
   prefix *name1 = stn1->name, *name2 = stn2->name;

#if 0
printf( "e = ( %.2f, %.2f, %.2f )", e[0], e[1], e[2] );
printf( " v = ( %.2f, %.2f, %.2f )\n", v[0], v[1], v[2] );
#endif
   hsqrd = sqrd(v[0]) + sqrd(v[1]);
   rsqrd = hsqrd + sqrd(v[2]);
   if (rsqrd == 0.0) return;

   cx = v[0] + e[0];
   cy = v[1] + e[1];
   cz = v[2] + e[2];

   s = (e[0] * v[0] + e[1] * v[1] + e[2] * v[2]) / rsqrd;
   tot = 0;
   for (i = 2; i >= 0; i--) tot += sqrd(e[i] - v[i] * s);

   if (tot <= expected_error) {
      if (!output) {
         fprint_prefix(fhErrStat, name1);
         fputs("->", fhErrStat);
         fprint_prefix(fhErrStat, name2);
      }
      fprintf(fhErrStat, " L: %.2f", sqrt(tot));
      /* checked - works */
      fprintf(fhErrStat, " (%.2fm -> %.2fm)", sqrt(sqrdd(v)), sqrt(sqrdd(v)) * (1 - s));
      output = 1;
   }

   s = sqrd(cx) + sqrd(cy);
   if (s > 0.0) {
      s = hsqrd / s;
      SVX_ASSERT(s >= 0.0);
      s = sqrt(s);
      s = 1 - s;
      tot = sqrd(cx * s) + sqrd(cy * s) + sqrd(e[2]);
      if (tot <= expected_error) {
         double newval, oldval;
         if (!output) {
            fprint_prefix(fhErrStat, name1);
            fputs("->", fhErrStat);
            fprint_prefix(fhErrStat, name2);
         }
         fprintf(fhErrStat, " B: %.2f", sqrt(tot));
         /* checked - works */
         newval = deg(atan2(cx, cy));
         if (newval < 0) newval += 360;
         oldval = deg(atan2(v[0], v[1]));
         if (oldval < 0) oldval += 360;
         fprintf(fhErrStat, " (%.2fdeg -> %.2fdeg)", oldval, newval);
         output = 1;
      }
   }

   if (hsqrd > 0.0) {
      double nx, ny;
      s = (e[0] * v[1] - e[1] * v[0]) / hsqrd;
      nx = cx - s * v[1];
      ny = cy + s * v[0];
      s = sqrd(nx) + sqrd(ny) + sqrd(cz);
      if (s > 0.0) {
         s = rsqrd / s;
         SVX_ASSERT(s >= 0);
         s = sqrt(s);
         tot = sqrd(cx - s * nx) + sqrd(cy - s * ny) + sqrd(cz - s * cz);
         if (tot <= expected_error) {
            if (!output) {
               fprint_prefix(fhErrStat, name1);
               fputs("->", fhErrStat);
               fprint_prefix(fhErrStat, name2);
            }
            fprintf(fhErrStat, " G: %.2f", sqrt(tot));
            /* checked - works */
            fprintf(fhErrStat, " (%.2fdeg -> %.2fdeg)",
                    deg(atan2(v[2], sqrt(v[0] * v[0] + v[1] * v[1]))),
                    deg(atan2(cz, sqrt(nx * nx + ny * ny))));
            output = 1;
         }
      }
   }
   if (output) fputnl(fhErrStat);
}
#endif

static void
replace_travs(void)
{
   stack *ptrOld;
   node *stn1, *stn2, *stn3;
   int i, j, k;
   double eTot = 0, lenTrav = 0, lenTot;
   double eTotTheo = 0;
   double vTot = 0, vTotTheo = 0, hTot = 0, hTotTheo = 0;
   delta e, sc;
   bool fEquate; /* used to indicate equates in output */
   int cLegsTrav = 0;
   bool fArtic;

   out_current_action(msg(/*Calculating traverses*/127));

   if (!fhErrStat && !fSuppress)
      fhErrStat = safe_fopen_with_ext(fnm_output_base, EXT_SVX_ERRS, "w");

   if (!pimg) {
      char *fnm = add_ext(fnm_output_base, EXT_SVX_3D);
      filename_register_output(fnm);
      pimg = img_open_write(fnm, survey_title, 0);
      if (!pimg) fatalerror(img_error(), fnm);
      osfree(fnm);
   }

   /* First do all the one leg traverses */
   FOR_EACH_STN(stn1, stnlist) {
#if PRINT_NETBITS
      printf("One leg traverses from ");
      print_prefix(stn1->name);
      printf(" [%p]\n", stn1);
#endif
      for (i = 0; i <= 2; i++) {
         linkfor *leg = stn1->leg[i];
         if (leg && data_here(leg) &&
             !(leg->l.reverse & (FLAG_REPLACEMENTLEG | FLAG_FAKE))) {
            SVX_ASSERT(fixed(stn1));
            SVX_ASSERT(!fZeros(&leg->v));

            stn2 = leg->l.to;
            if (TSTBIT(leg->l.flags, FLAGS_SURFACE)) {
               stn1->name->sflags |= BIT(SFLAGS_SURFACE);
               stn2->name->sflags |= BIT(SFLAGS_SURFACE);
            } else {
               stn1->name->sflags |= BIT(SFLAGS_UNDERGROUND);
               stn2->name->sflags |= BIT(SFLAGS_UNDERGROUND);
            }
            img_write_item(pimg, img_MOVE, 0, NULL,
                           POS(stn1, 0), POS(stn1, 1), POS(stn1, 2));
            if (leg->meta) {
                pimg->days1 = leg->meta->days1;
                pimg->days2 = leg->meta->days2;
            } else {
                pimg->days1 = pimg->days2 = -1;
            }
            pimg->style = (leg->l.flags >> FLAGS_STYLE_BIT0) & 0x07;
            img_write_item(pimg, img_LINE, leg->l.flags & FLAGS_MASK,
                           sprint_prefix(stn1->name->up),
                           POS(stn2, 0), POS(stn2, 1), POS(stn2, 2));
            if (!(leg->l.reverse & FLAG_ARTICULATION)) {
#ifdef BLUNDER_DETECTION
               delta err;
               int do_blunder;
#else
               if (fhErrStat) {
                  fprint_prefix(fhErrStat, stn1->name);
                  fputs(szLink, fhErrStat);
                  fprint_prefix(fhErrStat, stn2->name);
               }
#endif
               subdd(&e, &POSD(stn2), &POSD(stn1));
               subdd(&e, &e, &leg->d);
               if (fhErrStat) {
                  eTot = sqrdd(e);
                  hTot = sqrd(e[0]) + sqrd(e[1]);
                  vTot = sqrd(e[2]);
#ifndef NO_COVARIANCES
                  /* FIXME: what about covariances? */
                  hTotTheo = leg->v[0] + leg->v[1];
                  vTotTheo = leg->v[2];
                  eTotTheo = hTotTheo + vTotTheo;
#else
                  hTotTheo = leg->v[0] + leg->v[1];
                  vTotTheo = leg->v[2];
                  eTotTheo = hTotTheo + vTotTheo;
#endif
#ifdef BLUNDER_DETECTION
                  memcpy(&err, &e, sizeof(delta));
                  do_blunder = (eTot > eTotTheo);
                  fputs("\ntraverse ", fhErrStat);
                  fprint_prefix(fhErrStat, stn1->name);
                  fputs("->", fhErrStat);
                  fprint_prefix(fhErrStat, stn2->name);
                  fprintf(fhErrStat, " e=(%.2f, %.2f, %.2f) mag=%.2f %s\n",
                          e[0], e[1], e[2], sqrt(eTot),
                          (do_blunder ? "suspect:" : "OK"));
                  if (do_blunder)
                     do_gross(err, leg->d, stn1, stn2, eTotTheo);
#endif
                  err_stat(1, sqrt(sqrdd(leg->d)), eTot, eTotTheo,
                           hTot, hTotTheo, vTot, vTotTheo);
               }
            }
         }
      }
   }

   while (ptr != NULL) {
      /* work out where traverse should be reconnected */
      linkfor *leg = ptr->join1;
      leg = reverse_leg(leg);
      stn1 = leg->l.to;
      i = reverse_leg_dirn(leg);

      leg = ptr->join2;
      leg = reverse_leg(leg);
      stn2 = leg->l.to;
      j = reverse_leg_dirn(leg);

#if PRINT_NETBITS
      printf(" Trav ");
      print_prefix(stn1->name);
      printf("<%p>[%d]%s...%s", stn1, i, szLink, szLink);
      print_prefix(stn2->name);
      printf("<%p>[%d]\n", stn2, j);
#endif

      SVX_ASSERT(fixed(stn1));
      SVX_ASSERT(fixed(stn2));

      /* calculate scaling factors for error distribution */
      eTot = 0.0;
      hTot = vTot = 0.0;
      SVX_ASSERT(data_here(stn1->leg[i]));
      if (fZeros(&stn1->leg[i]->v)) {
         sc[0] = sc[1] = sc[2] = 0.0;
      } else {
         subdd(&e, &POSD(stn2), &POSD(stn1));
         subdd(&e, &e, &stn1->leg[i]->d);
         eTot = sqrdd(e);
         hTot = sqrd(e[0]) + sqrd(e[1]);
         vTot = sqrd(e[2]);
         divds(&sc, &e, &stn1->leg[i]->v);
      }
#ifndef NO_COVARIANCES
      /* FIXME: what about covariances? */
      hTotTheo = stn1->leg[i]->v[0] + stn1->leg[i]->v[1];
      vTotTheo = stn1->leg[i]->v[2];
#else
      hTotTheo = stn1->leg[i]->v[0] + stn1->leg[i]->v[1];
      vTotTheo = stn1->leg[i]->v[2];
#endif
      eTotTheo = hTotTheo + vTotTheo;
      cLegsTrav = 0;
      lenTrav = 0.0;
      img_write_item(pimg, img_MOVE, 0, NULL,
                     POS(stn1, 0), POS(stn1, 1), POS(stn1, 2));

      fArtic = stn1->leg[i]->l.reverse & FLAG_ARTICULATION;
      osfree(stn1->leg[i]);
      stn1->leg[i] = ptr->join1; /* put old link back in */

      osfree(stn2->leg[j]);
      stn2->leg[j] = ptr->join2; /* and the other end */

#ifdef BLUNDER_DETECTION
      delta err;
      int do_blunder;
      memcpy(&err, &e, sizeof(delta));
      do_blunder = (eTot > eTotTheo);
      if (fhErrStat && !fArtic) {
         fputs("\ntraverse ", fhErrStat);
         fprint_prefix(fhErrStat, stn1->name);
         fputs("->", fhErrStat);
         fprint_prefix(fhErrStat, stn2->name);
         fprintf(fhErrStat, " e=(%.2f, %.2f, %.2f) mag=%.2f %s\n",
                 e[0], e[1], e[2], sqrt(eTot),
                 (do_blunder ? "suspect:" : "OK"));
      }
#endif
      while (fTrue) {
         int reached_end;
         prefix *leg_pfx;

         fEquate = fTrue;
         /* get next node in traverse
          * should have stn3->leg[k]->l.to == stn1 */
         stn3 = stn1->leg[i]->l.to;
         k = reverse_leg_dirn(stn1->leg[i]);
         SVX_ASSERT2(stn3->leg[k]->l.to == stn1,
                 "reverse leg doesn't reciprocate");

         reached_end = (stn3 == stn2 && k == j);

         if (data_here(stn1->leg[i])) {
            leg_pfx = stn1->name->up;
            leg = stn1->leg[i];
#ifdef BLUNDER_DETECTION
            if (do_blunder && fhErrStat)
               do_gross(err, leg->d, stn1, stn3, eTotTheo);
#endif
            if (!reached_end)
               adddd(&POSD(stn3), &POSD(stn1), &leg->d);
         } else {
            leg_pfx = stn3->name->up;
            leg = stn3->leg[k];
#ifdef BLUNDER_DETECTION
            if (do_blunder && fhErrStat)
               do_gross(err, leg->d, stn1, stn3, eTotTheo);
#endif
            if (!reached_end)
               subdd(&POSD(stn3), &POSD(stn1), &leg->d);
         }

         lenTot = sqrdd(leg->d);

         if (!fZeros(&leg->v)) fEquate = fFalse;
         if (!reached_end) {
            add_stn_to_list(&stnlist, stn3);
            if (!fEquate) {
               mulsd(&e, &leg->v, &sc);
               adddd(&POSD(stn3), &POSD(stn3), &e);
            }
            fix(stn3);
         }

         if (!(leg->l.reverse & (FLAG_REPLACEMENTLEG | FLAG_FAKE))) {
             if (TSTBIT(leg->l.flags, FLAGS_SURFACE)) {
                stn1->name->sflags |= BIT(SFLAGS_SURFACE);
                stn3->name->sflags |= BIT(SFLAGS_SURFACE);
             } else {
                stn1->name->sflags |= BIT(SFLAGS_UNDERGROUND);
                stn3->name->sflags |= BIT(SFLAGS_UNDERGROUND);
             }

            SVX_ASSERT(!fEquate);
            SVX_ASSERT(!fZeros(&leg->v));
            if (leg->meta) {
                pimg->days1 = leg->meta->days1;
                pimg->days2 = leg->meta->days2;
            } else {
                pimg->days1 = pimg->days2 = -1;
            }
            pimg->style = (leg->l.flags >> FLAGS_STYLE_BIT0) & 0x07;
            img_write_item(pimg, img_LINE, leg->l.flags & FLAGS_MASK,
                           sprint_prefix(leg_pfx),
                           POS(stn3, 0), POS(stn3, 1), POS(stn3, 2));
         }

         /* FIXME: equate at the start of a traverse treated specially
          * - what about equates at end? */
         if (stn1->name != stn3->name && !(fEquate && cLegsTrav == 0)) {
            /* (node not part of same stn) &&
             * (not equate at start of traverse) */
#ifndef BLUNDER_DETECTION
            if (fhErrStat && !fArtic) {
               if (!stn1->name->ident) {
                  /* FIXME: not ideal */
                  fputs("<fixed point>", fhErrStat);
               } else {
                  fprint_prefix(fhErrStat, stn1->name);
               }
               fputs(fEquate ? szLinkEq : szLink, fhErrStat);
               if (reached_end) {
                  if (!stn3->name->ident) {
                     /* FIXME: not ideal */
                     fputs("<fixed point>", fhErrStat);
                  } else {
                     fprint_prefix(fhErrStat, stn3->name);
                  }
               }
            }
#endif
            if (!fEquate) {
               cLegsTrav++;
               lenTrav += sqrt(lenTot);
            }
         } else {
#if SHOW_INTERNAL_LEGS
            if (fhErrStat && !fArtic) fprintf(fhErrStat, "+");
#endif
            if (lenTot > 0.0) {
#if DEBUG_INVALID
               fprintf(stderr, "lenTot = %8.4f ", lenTot);
               fprint_prefix(stderr, stn1->name);
               fprintf(stderr, " -> ");
               fprint_prefix(stderr, stn3->name);
#endif
               BUG("during calculation of closure errors");
            }
         }
         if (reached_end) break;

         i = k ^ 1; /* flip direction for other leg of 2 node */

         stn1 = stn3;
      } /* endwhile */

      if (cLegsTrav && !fArtic && fhErrStat)
         err_stat(cLegsTrav, lenTrav, eTot, eTotTheo,
                  hTot, hTotTheo, vTot, vTotTheo);

      ptrOld = ptr;
      ptr = ptr->next;
      osfree(ptrOld);
   }

   /* Leave fhErrStat open in case we're asked to close loops again... */
}

static void
err_stat(int cLegsTrav, double lenTrav,
         double eTot, double eTotTheo,
         double hTot, double hTotTheo,
         double vTot, double vTotTheo)
{
   double E = sqrt(eTot / eTotTheo);
   double H = sqrt(hTot / hTotTheo);
   double V = sqrt(vTot / vTotTheo);
   if (!fSuppress) {
      double sqrt_eTot = sqrt(eTot);
      fputnl(fhErrStat);
      fprintf(fhErrStat, msg(/*Original length %6.2fm (%3d legs), moved %6.2fm (%5.2fm/leg). */145),
              lenTrav, cLegsTrav, sqrt_eTot, sqrt_eTot / cLegsTrav);
      if (lenTrav > 0.0)
         fprintf(fhErrStat, msg(/*Error %6.2f%%*/146), 100 * sqrt_eTot / lenTrav);
      else
         fputs(msg(/*Error    N/A*/147), fhErrStat);
      fputnl(fhErrStat);
      fprintf(fhErrStat, "%f\n", E);
      fprintf(fhErrStat, "H: %f V: %f\n", H, V);
      fputnl(fhErrStat);
   }
   img_write_errors(pimg, cLegsTrav, lenTrav, E, H, V);
}

static void
replace_trailing_travs(void)
{
   stackTrail *ptrOld;
   node *stn1, *stn2;
   linkfor *leg;
   int i;

   out_current_action(msg(/*Calculating trailing traverses*/128));

   while (ptrTrail != NULL) {
      leg = ptrTrail->join1;
      leg = reverse_leg(leg);
      stn1 = leg->l.to;
      i = reverse_leg_dirn(leg);
#if PRINT_NETBITS
      printf(" Trailing trav ");
      print_prefix(stn1->name);
      printf("<%p>", stn1);
      printf("%s...\n", szLink);
      printf("    attachment stn is at (%f, %f, %f)\n",
             POS(stn1, 0), POS(stn1, 1), POS(stn1, 2));
#endif
      /* We may have swapped the links round when we removed the leg.  If
       * we did then stn1->leg[i] will be in use.  The link we swapped
       * with is the first free leg */
      if (stn1->leg[i]) {
         /* j is the direction to swap with */
         int j = (stn1->leg[1]) ? 2 : 1;
         /* change the other direction of leg i to use leg j */
         reverse_leg(stn1->leg[i])->l.reverse += j - i;
         stn1->leg[j] = stn1->leg[i];
      }
      stn1->leg[i] = ptrTrail->join1;
      SVX_ASSERT(fixed(stn1));
      img_write_item(pimg, img_MOVE, 0, NULL,
                     POS(stn1, 0), POS(stn1, 1), POS(stn1, 2));

      while (1) {
         prefix *leg_pfx;
         int j;

         leg = stn1->leg[i];
         stn2 = leg->l.to;
         j = reverse_leg_dirn(leg);
         if (data_here(leg)) {
            leg_pfx = stn1->name->up;
            adddd(&POSD(stn2), &POSD(stn1), &leg->d);
#if 0
            printf("Adding leg (%f, %f, %f)\n", leg->d[0], leg->d[1], leg->d[2]);
#endif
         } else {
            leg_pfx = stn2->name->up;
            leg = stn2->leg[j];
            subdd(&POSD(stn2), &POSD(stn1), &leg->d);
#if 0
            printf("Subtracting reverse leg (%f, %f, %f)\n", leg->d[0], leg->d[1], leg->d[2]);
#endif
         }

         fix(stn2);
         add_stn_to_list(&stnlist, stn2);
         if (!(leg->l.reverse & (FLAG_REPLACEMENTLEG | FLAG_FAKE))) {
             if (TSTBIT(leg->l.flags, FLAGS_SURFACE)) {
                stn1->name->sflags |= BIT(SFLAGS_SURFACE);
                stn2->name->sflags |= BIT(SFLAGS_SURFACE);
             } else {
                stn1->name->sflags |= BIT(SFLAGS_UNDERGROUND);
                stn2->name->sflags |= BIT(SFLAGS_UNDERGROUND);
             }
         }
         if (!(leg->l.reverse & (FLAG_REPLACEMENTLEG | FLAG_FAKE))) {
            SVX_ASSERT(!fZeros(&leg->v));
            if (leg->meta) {
                pimg->days1 = leg->meta->days1;
                pimg->days2 = leg->meta->days2;
            } else {
                pimg->days1 = pimg->days2 = -1;
            }
            pimg->style = (leg->l.flags >> FLAGS_STYLE_BIT0) & 0x07;
            img_write_item(pimg, img_LINE, leg->l.flags & FLAGS_MASK,
                           sprint_prefix(leg_pfx),
                           POS(stn2, 0), POS(stn2, 1), POS(stn2, 2));
         }

         /* stop if not 2 node */
         if (!two_node(stn2)) break;

         stn1 = stn2;
         i = j ^ 1; /* flip direction for other leg of 2 node */
      }

      ptrOld = ptrTrail;
      ptrTrail = ptrTrail->next;
      osfree(ptrOld);
   }

   /* write out connections with no survey data */
   while (nosurveyhead) {
      nosurveylink *p = nosurveyhead;
      SVX_ASSERT(fixed(p->fr));
      SVX_ASSERT(fixed(p->to));
      if (TSTBIT(p->flags, FLAGS_SURFACE)) {
         p->fr->name->sflags |= BIT(SFLAGS_SURFACE);
         p->to->name->sflags |= BIT(SFLAGS_SURFACE);
      } else {
         p->fr->name->sflags |= BIT(SFLAGS_UNDERGROUND);
         p->to->name->sflags |= BIT(SFLAGS_UNDERGROUND);
      }
      img_write_item(pimg, img_MOVE, 0, NULL,
                     POS(p->fr, 0), POS(p->fr, 1), POS(p->fr, 2));
      if (p->meta) {
          pimg->days1 = p->meta->days1;
          pimg->days2 = p->meta->days2;
      } else {
          pimg->days1 = pimg->days2 = -1;
      }
      pimg->style = img_STYLE_NOSURVEY;
      img_write_item(pimg, img_LINE, (p->flags & FLAGS_MASK),
                     sprint_prefix(p->fr->name->up),
                     POS(p->to, 0), POS(p->to, 1), POS(p->to, 2));
      nosurveyhead = p->next;
      osfree(p);
   }

   /* write stations to .3d file and free legs and stations */
   FOR_EACH_STN(stn1, stnlist) {
      int d;
      SVX_ASSERT(fixed(stn1));
      if (stn1->name->stn == stn1) {
         int sf = stn1->name->sflags;
         /* take care of unused fixed points */
         if (!TSTBIT(sf, SFLAGS_SOLVED)) {
            const char * label = NULL;
            if (TSTBIT(sf, SFLAGS_ANON)) {
               label = "";
            } else if (stn1->name->ident) {
               label = sprint_prefix(stn1->name);
            }
            if (label) {
               /* Set flag to stop station being rewritten after *solve. */
               stn1->name->sflags = sf | BIT(SFLAGS_SOLVED);
               sf &= SFLAGS_MASK;
               if (stn1->name->max_export) sf |= BIT(SFLAGS_EXPORTED);
               img_write_item(pimg, img_LABEL, sf, label,
                              POS(stn1, 0), POS(stn1, 1), POS(stn1, 2));
            }
         }
      }
      /* update coords of bounding box, ignoring the base positions
       * of points fixed with error estimates and only counting stations
       * in underground surveys.
       *
       * NB We don't set SFLAGS_UNDERGROUND for the anchor station for
       * a point fixed with error estimates, so this test will exclude
       * those too, which is what we want.
       */
      if (TSTBIT(stn1->name->sflags, SFLAGS_UNDERGROUND)) {
         for (d = 0; d < 3; d++) {
            if (POS(stn1, d) < min[d]) {
               min[d] = POS(stn1, d);
               pfxLo[d] = stn1->name;
            }
            if (POS(stn1, d) > max[d]) {
               max[d] = POS(stn1, d);
               pfxHi[d] = stn1->name;
            }
         }
      }

      d = stn1->name->shape;
      if (d <= 1 && !TSTBIT(stn1->name->sflags, SFLAGS_USED)) {
         bool unused_fixed_point = fFalse;
         if (d == 0) {
            /* Unused fixed point without error estimates */
            unused_fixed_point = fTrue;
         } else if (stn1->leg[0]) {
            prefix *pfx = stn1->leg[0]->l.to->name;
            if (!pfx->ident && !TSTBIT(pfx->sflags, SFLAGS_ANON)) {
               /* Unused fixed point with error estimates */
               unused_fixed_point = fTrue;
            }
         }
         if (unused_fixed_point) {
            warning_in_file(stn1->name->filename, stn1->name->line,
                    /*Unused fixed point “%s”*/73, sprint_prefix(stn1->name));
         }
      }

      /* For stations fixed with error estimates, we need to ignore the leg to
       * the "real" fixed point in the node stats.
       */
      if (stn1->leg[0] && !stn1->leg[0]->l.to->name->ident &&
          !TSTBIT(stn1->leg[0]->l.to->name->sflags, SFLAGS_ANON))
         stn1->name->shape--;

      for (i = 0; i <= 2; i++) {
         leg = stn1->leg[i];
         /* only want to think about forwards legs */
         if (leg && data_here(leg)) {
            linkfor *legRev;
            node *stnB;
            int iB;
            stnB = leg->l.to;
            iB = reverse_leg_dirn(leg);
            legRev = stnB->leg[iB];
            SVX_ASSERT2(legRev->l.to == stn1, "leg doesn't reciprocate");
            SVX_ASSERT(fixed(stn1));
            if (!(leg->l.flags &
                  (BIT(FLAGS_DUPLICATE)|BIT(FLAGS_SPLAY)|
                   BIT(FLAGS_SURFACE)))) {
               /* check not an equating leg, or one inside an sdfix point */
               if (!(leg->l.reverse & (FLAG_REPLACEMENTLEG | FLAG_FAKE))) {
                  totadj += sqrt(sqrd(POS(stnB, 0) - POS(stn1, 0)) +
                                 sqrd(POS(stnB, 1) - POS(stn1, 1)) +
                                 sqrd(POS(stnB, 2) - POS(stn1, 2)));
                  total += sqrt(sqrdd(leg->d));
                  totplan += hypot(leg->d[0], leg->d[1]);
                  totvert += fabs(leg->d[2]);
               }
            }
            osfree(leg);
            osfree(legRev);
            stn1->leg[i] = stnB->leg[iB] = NULL;
         }
      }
   }

   /* The station position is attached to the name, so we leave the names and
    * positions in place - they can then be picked up if we have a *solve
    * followed by more data */
   for (stn1 = stnlist; stn1; stn1 = stn2) {
      stn2 = stn1->next;
      stn1->name->stn = NULL;
      osfree(stn1);
   }
   stnlist = NULL;
}

static void
write_passage_models(void)
{
   lrudlist * psg = model;
   while (psg) {
      lrudlist * oldp;
      lrud * xsect = psg->tube;
      int xflags = 0;
      while (xsect) {
         lrud *oldx;
         prefix *pfx;
         const char *name;
         pimg->l = xsect->l;
         pimg->r = xsect->r;
         pimg->u = xsect->u;
         pimg->d = xsect->d;
         if (xsect->meta) {
             pimg->days1 = xsect->meta->days1;
             pimg->days2 = xsect->meta->days2;
         } else {
             pimg->days1 = pimg->days2 = -1;
         }

         pfx = xsect->stn;
         name = sprint_prefix(pfx);
         oldx = xsect;
         xsect = xsect->next;
         osfree(oldx);

         if (!pfx->pos) {
             error_in_file(pfx->filename, pfx->line,
                           /*Cross section specified at non-existent station “%s”*/83,
                           name);
         } else {
             if (xsect == NULL) xflags = img_XFLAG_END;
             img_write_item(pimg, img_XSECT, xflags, name, 0, 0, 0);
         }
      }
      oldp = psg;
      psg = psg->next;
      osfree(oldp);
   }
   model = NULL;
}