3 // dem.c -- DEM management class
5 // Written by Curtis Olson, started March 1998.
7 // Copyright (C) 1998 Curtis L. Olson - curt@me.umn.edu
9 // This program is free software; you can redistribute it and/or
10 // modify it under the terms of the GNU General Public License as
11 // published by the Free Software Foundation; either version 2 of the
12 // License, or (at your option) any later version.
14 // This program is distributed in the hope that it will be useful, but
15 // WITHOUT ANY WARRANTY; without even the implied warranty of
16 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 // General Public License for more details.
19 // You should have received a copy of the GNU General Public License
20 // along with this program; if not, write to the Free Software
21 // Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24 // (Log is kept at end of this file)
31 #include <Include/compiler.h>
33 #include <ctype.h> // isspace()
34 #include <stdlib.h> // atoi()
35 #include <math.h> // rint()
38 #ifdef HAVE_SYS_STAT_H
39 # include <sys/stat.h> // stat()
41 #ifdef FG_HAVE_STD_INCLUDES
47 # include <unistd.h> // stat()
53 // #include <zlib/zlib.h>
54 #include <Misc/fgstream.hxx>
55 #include <Misc/strutils.hxx>
56 #include <Include/compiler.h>
58 FG_USING_NAMESPACE(std);
61 // #include "leastsqs.hxx"
63 #include <Include/fg_constants.h>
66 #define MAX_EX_NODES 10000
72 # define MKDIR(a) mkdir(a)
74 # define MKDIR(a) mkdir(a,S_IRWXU) // I am just guessing at this flag (NHV)
75 # endif // __BORLANDC__
80 FGDem::FGDem( void ) {
81 // cout << "class FGDem CONstructor called." << endl;
82 dem_data = new float[DEM_SIZE_1][DEM_SIZE_1];
83 output_data = new float[DEM_SIZE_1][DEM_SIZE_1];
87 FGDem::FGDem( const string &file ) {
88 // cout << "class FGDem CONstructor called." << endl;
89 dem_data = new float[DEM_SIZE_1][DEM_SIZE_1];
90 output_data = new float[DEM_SIZE_1][DEM_SIZE_1];
98 FGDem::open ( const string& file ) {
99 // open input file (or read from stdin)
101 printf("Loading DEM data file: stdin\n");
103 // fd = gzdopen(STDIN_FILENO, "r");
104 printf("Not yet ported ...\n");
107 in = new fg_gzifstream( file );
109 cout << "Cannot open " << file << endl;
112 cout << "Loading DEM data file: " << file << endl;
122 // the fg_gzifstream doesn't seem to have a close()
130 // return next token from input stream
132 FGDem::next_token() {
137 // cout << " returning " + token + "\n";
143 // return next integer from input stream
154 // return next double from input stream
156 FGDem::next_double() {
165 // return next exponential num from input stream
173 token = next_token();
176 const char* p = token.c_str();
180 for ( ; *p != 0; ++p )
188 return ::atof( buf );
190 sscanf(token.c_str(), "%lfD%d", &mantissa, &exp);
192 // cout << " Mantissa = " << mantissa << " Exp = " << exp << "\n";
196 for ( i = 1; i <= exp; i++ ) {
199 } else if ( exp < 0 ) {
200 for ( i = -1; i >= exp; i-- ) {
205 return( (int)rint(mantissa * (double)acc) );
210 // read and parse DEM "A" record
212 FGDem::read_a_record() {
219 // get the name field (144 characters)
220 for ( i = 0; i < 144; i++ ) {
225 // clean off the trailing whitespace
227 cout << " Quad name field: " << name << endl;
229 // DEM level code, 3 reflects processing by DMA
231 cout << " DEM level code = " << inum << "\n";
237 // Pattern code, 1 indicates a regular elevation pattern
239 cout << " Pattern code = " << inum << "\n";
241 // Planimetric reference system code, 0 indicates geographic
242 // coordinate system.
244 cout << " Planimetric reference code = " << inum << "\n";
248 cout << " Zone code = " << inum << "\n";
250 // Map projection parameters (ignored)
251 for ( i = 0; i < 15; i++ ) {
253 // printf("%d: %f\n",i,dnum);
256 // Units code, 3 represents arc-seconds as the unit of measure for
257 // ground planimetric coordinates throughout the file.
260 cout << " Unknown (X,Y) units code = " << inum << "!\n";
264 // Units code; 2 represents meters as the unit of measure for
265 // elevation coordinates throughout the file.
268 cout << " Unknown (Z) units code = " << inum << "!\n";
272 // Number (n) of sides in the polygon which defines the coverage of
273 // the DEM file (usually equal to 4).
276 cout << " Unknown polygon dimension = " << inum << "!\n";
280 // Ground coordinates of bounding box in arc-seconds
281 dem_x1 = originx = next_exp();
282 dem_y1 = originy = next_exp();
283 cout << " Origin = (" << originx << "," << originy << ")\n";
294 // Minimum/maximum elevations in meters
297 cout << " Elevation range " << dem_z1 << " to " << dem_z2 << "\n";
299 // Counterclockwise angle from the primary axis of ground
300 // planimetric referenced to the primary axis of the DEM local
302 token = next_token();
304 // Accuracy code; 0 indicates that a record of accuracy does not
305 // exist and that no record type C will follow.
307 // DEM spacial resolution. Usually (3,3,1) (3,6,1) or (3,9,1)
308 // depending on latitude
310 // I will eventually have to do something with this for data at
311 // higher latitudes */
312 token = next_token();
313 cout << " accuracy & spacial resolution string = " << token << endl;
315 cout << " length = " << i << "\n";
317 inum = atoi( token.substr( 0, i - 36 ) );
318 row_step = atof( token.substr( i - 24, 12 ) );
319 col_step = atof( token.substr( i - 36, 12 ) );
320 cout << " Accuracy code = " << inum << "\n";
321 cout << " column step = " << col_step <<
322 " row step = " << row_step << "\n";
324 // dimension of arrays to follow (1)
325 token = next_token();
327 // number of profiles
328 dem_num_profiles = cols = next_int();
329 cout << " Expecting " << dem_num_profiles << " profiles\n";
335 // read and parse DEM "B" record
337 FGDem::read_b_record( ) {
341 // row / column id of this profile
342 prof_row = next_int();
343 prof_col = next_int();
344 // printf("col id = %d row id = %d\n", prof_col, prof_row);
346 // Number of columns and rows (elevations) in this profile
347 prof_num_rows = rows = next_int();
348 prof_num_cols = next_int();
349 // printf(" profile num rows = %d\n", prof_num_rows);
351 // Ground planimetric coordinates (arc-seconds) of the first
352 // elevation in the profile
353 prof_x1 = next_exp();
354 prof_y1 = next_exp();
355 // printf(" Starting at %.2f %.2f\n", prof_x1, prof_y1);
357 // Elevation of local datum for the profile. Always zero for
358 // 1-degree DEM, the reference is mean sea level.
359 token = next_token();
361 // Minimum and maximum elevations for the profile.
362 token = next_token();
363 token = next_token();
365 // One (usually) dimensional array (prof_num_cols,1) of elevations
366 for ( i = 0; i < prof_num_rows; i++ ) {
367 prof_data = next_int();
368 dem_data[cur_col][i] = (float)prof_data;
380 if ( !read_a_record() ) {
384 for ( i = 0; i < dem_num_profiles; i++ ) {
385 // printf("Ready to read next b record\n");
389 if ( cur_col % 100 == 0 ) {
390 cout << " loaded " << cur_col << " profiles of data\n";
394 cout << " Done parsing\n";
400 // write out the area of data covered by the specified bucket. Data
401 // is written out column by column starting at the lower left hand
404 FGDem::write_area( const string& root, FGBucket& b, bool compress ) {
407 // calculate some boundaries
408 double min_x = ( b.get_center_lon() - 0.5 * b.get_width() ) * 3600.0;
409 double max_x = ( b.get_center_lon() + 0.5 * b.get_width() ) * 3600.0;
411 double min_y = ( b.get_center_lat() - 0.5 * b.get_height() ) * 3600.0;
412 double max_y = ( b.get_center_lat() + 0.5 * b.get_height() ) * 3600.0;
415 cout << "width = " << b.get_width() << " height = " << b.get_height()
418 int start_x = (int)((min_x - originx) / col_step);
419 int span_x = (int)(b.get_width() * 3600.0 / col_step);
421 int start_y = (int)((min_y - originy) / row_step);
422 int span_y = (int)(b.get_height() * 3600.0 / row_step);
424 cout << "start_x = " << start_x << " span_x = " << span_x << endl;
425 cout << "start_y = " << start_y << " span_y = " << span_y << endl;
427 // Do a simple sanity checking. But, please, please be nice to
428 // this write_area() routine and feed it buckets that coincide
429 // well with the underlying grid structure and spacing.
431 if ( ( min_x < originx )
432 || ( max_x > originx + cols * col_step )
433 || ( min_y < originy )
434 || ( max_y > originy + rows * row_step ) ) {
435 cout << " ERROR: bucket at least partially outside DEM data range!" <<
440 // generate output file name
441 string base = b.gen_base_path();
442 string path = root + "/Scenery/" + base;
443 string command = "mkdir -p " + path;
444 system( command.c_str() );
446 long int b_index = b.gen_index();
447 sprintf(tile_name, "%ld", b_index);
448 string demfile = path + "/" + tile_name + ".dem";
449 cout << "demfile = " << demfile << endl;
453 if ( (fp = fopen(demfile.c_str(), "w")) == NULL ) {
454 cout << "cannot open " << demfile << " for writing!" << endl;
458 fprintf( fp, "%d %d\n", (int)min_x, (int)min_y );
459 fprintf( fp, "%d %d %d %d\n", span_x + 1, (int)col_step,
460 span_y + 1, (int)row_step );
461 for ( int i = start_x; i <= start_x + span_x; ++i ) {
462 for ( int j = start_y; j <= start_y + span_y; ++j ) {
463 fprintf( fp, "%d ", (int)dem_data[i][j] );
470 string command = "gzip --best -f " + demfile;
471 system( command.c_str() );
478 // return the current altitude based on grid data. We should rewrite
479 // this to interpolate exact values, but for now this is good enough
480 double FGDem::interpolate_altitude( double lon, double lat ) {
481 // we expect incoming (lon,lat) to be in arcsec for now
483 double xlocal, ylocal, dx, dy, zA, zB, elev;
484 int x1, x2, x3, y1, y2, y3;
488 /* determine if we are in the lower triangle or the upper triangle
496 then calculate our end points
499 xlocal = (lon - originx) / col_step;
500 ylocal = (lat - originy) / row_step;
502 xindex = (int)(xlocal);
503 yindex = (int)(ylocal);
505 // printf("xindex = %d yindex = %d\n", xindex, yindex);
507 if ( xindex + 1 == cols ) {
511 if ( yindex + 1 == rows ) {
515 if ( (xindex < 0) || (xindex + 1 >= cols) ||
516 (yindex < 0) || (yindex + 1 >= rows) ) {
520 dx = xlocal - xindex;
521 dy = ylocal - yindex;
525 // printf(" Lower triangle\n");
529 z1 = dem_data[x1][y1];
533 z2 = dem_data[x2][y2];
537 z3 = dem_data[x3][y3];
539 // printf(" dx = %.2f dy = %.2f\n", dx, dy);
540 // printf(" (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
541 // printf(" (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
542 // printf(" (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);
544 zA = dx * (z2 - z1) + z1;
545 zB = dx * (z3 - z1) + z1;
547 // printf(" zA = %.2f zB = %.2f\n", zA, zB);
549 if ( dx > FG_EPSILON ) {
550 elev = dy * (zB - zA) / dx + zA;
556 // printf(" Upper triangle\n");
560 z1 = dem_data[x1][y1];
564 z2 = dem_data[x2][y2];
568 z3 = dem_data[x3][y3];
570 // printf(" dx = %.2f dy = %.2f\n", dx, dy);
571 // printf(" (x1,y1,z1) = (%d,%d,%d)\n", x1, y1, z1);
572 // printf(" (x2,y2,z2) = (%d,%d,%d)\n", x2, y2, z2);
573 // printf(" (x3,y3,z3) = (%d,%d,%d)\n", x3, y3, z3);
575 zA = dy * (z2 - z1) + z1;
576 zB = dy * (z3 - z1) + z1;
578 // printf(" zA = %.2f zB = %.2f\n", zA, zB );
579 // printf(" xB - xA = %.2f\n", col_step * dy / row_step);
581 if ( dy > FG_EPSILON ) {
582 elev = dx * (zB - zA) / dy + zA;
592 // Use least squares to fit a simpler data set to dem data
593 void FGDem::fit( double error, FGBucket& p ) {
594 double x[DEM_SIZE_1], y[DEM_SIZE_1];
595 double m, b, ave_error, max_error;
597 int n, row, start, end;
598 int colmin, colmax, rowmin, rowmax;
600 // FILE *dem, *fit, *fit1;
602 printf("Initializing output mesh structure\n");
605 // determine dimensions
606 colmin = p.get_x() * ( (cols - 1) / 8);
607 colmax = colmin + ( (cols - 1) / 8);
608 rowmin = p.get_y() * ( (rows - 1) / 8);
609 rowmax = rowmin + ( (rows - 1) / 8);
610 printf("Fitting region = %d,%d to %d,%d\n", colmin, rowmin, colmax, rowmax);
612 // include the corners explicitly
613 outputmesh_set_pt(colmin, rowmin, dem_data[colmin][rowmin]);
614 outputmesh_set_pt(colmin, rowmax, dem_data[colmin][rowmax]);
615 outputmesh_set_pt(colmax, rowmax, dem_data[colmax][rowmax]);
616 outputmesh_set_pt(colmax, rowmin, dem_data[colmax][rowmin]);
618 printf("Beginning best fit procedure\n");
620 for ( row = rowmin; row <= rowmax; row++ ) {
621 // fit = fopen("fit.dat", "w");
622 // fit1 = fopen("fit1.dat", "w");
626 // printf(" fitting row = %d\n", row);
628 while ( start < colmax ) {
632 x[(end - start) - 1] = 0.0 + ( start * col_step );
633 y[(end - start) - 1] = dem_data[start][row];
635 while ( (end <= colmax) && good_fit ) {
636 n = (end - start) + 1;
637 // printf("Least square of first %d points\n", n);
638 x[end - start] = 0.0 + ( end * col_step );
639 y[end - start] = dem_data[end][row];
640 least_squares(x, y, n, &m, &b);
641 ave_error = least_squares_error(x, y, n, m, b);
642 max_error = least_squares_max_error(x, y, n, m, b);
645 printf("%d - %d ave error = %.2f max error = %.2f y = %.2f*x + %.2f\n",
646 start, end, ave_error, max_error, m, b);
648 f = fopen("gnuplot.dat", "w");
649 for ( j = 0; j <= end; j++) {
650 fprintf(f, "%.2f %.2f\n", 0.0 + ( j * col_step ),
653 for ( j = start; j <= end; j++) {
654 fprintf(f, "%.2f %.2f\n", 0.0 + ( j * col_step ),
659 printf("Please hit return: "); gets(junk);
662 if ( max_error > error ) {
670 // error exceeded the threshold, back up
671 end -= 2; // back "end" up to the last good enough fit
672 n--; // back "n" up appropriately too
674 // we popped out of the above loop while still within
675 // the error threshold, so we must be at the end of
680 least_squares(x, y, n, &m, &b);
681 ave_error = least_squares_error(x, y, n, m, b);
682 max_error = least_squares_max_error(x, y, n, m, b);
686 printf("%d - %d ave error = %.2f max error = %.2f y = %.2f*x + %.2f\n",
687 start, end, ave_error, max_error, m, b);
690 fprintf(fit1, "%.2f %.2f\n", x[0], m * x[0] + b);
691 fprintf(fit1, "%.2f %.2f\n", x[end-start], m * x[end-start] + b);
694 if ( start > colmin ) {
695 // skip this for the first line segment
697 outputmesh_set_pt(start, row, (lasty + cury) / 2);
698 // fprintf(fit, "%.2f %.2f\n", x[0], (lasty + cury) / 2);
701 lasty = m * x[end-start] + b;
709 dem = fopen("gnuplot.dat", "w");
710 for ( j = 0; j < DEM_SIZE_1; j++) {
711 fprintf(dem, "%.2f %.2f\n", 0.0 + ( j * col_step ),
717 // NOTICE, this is for testing only. This instance of
718 // output_nodes should be removed. It should be called only
719 // once at the end once all the nodes have been generated.
720 // newmesh_output_nodes(&nm, "mesh.node");
721 // printf("Please hit return: "); gets(junk);
724 // outputmesh_output_nodes(fg_root, p);
728 // Initialize output mesh structure
729 void FGDem::outputmesh_init( void ) {
732 for ( j = 0; j < DEM_SIZE_1; j++ ) {
733 for ( i = 0; i < DEM_SIZE_1; i++ ) {
734 output_data[i][j] = -9999.0;
740 // Get the value of a mesh node
741 double FGDem::outputmesh_get_pt( int i, int j ) {
742 return ( output_data[i][j] );
746 // Set the value of a mesh node
747 void FGDem::outputmesh_set_pt( int i, int j, double value ) {
748 // printf("Setting data[%d][%d] = %.2f\n", i, j, value);
749 output_data[i][j] = value;
753 // Write out a node file that can be used by the "triangle" program.
754 // Check for an optional "index.node.ex" file in case there is a .poly
755 // file to go along with this node file. Include these nodes first
756 // since they are referenced by position from the .poly file.
757 void FGDem::outputmesh_output_nodes( const string& fg_root, FGBucket& p )
759 double exnodes[MAX_EX_NODES][3];
760 struct stat stat_buf;
762 char file[256], exfile[256];
769 int colmin, colmax, rowmin, rowmax;
770 int i, j, count, excount, result;
772 // determine dimensions
773 colmin = p.get_x() * ( (cols - 1) / 8);
774 colmax = colmin + ( (cols - 1) / 8);
775 rowmin = p.get_y() * ( (rows - 1) / 8);
776 rowmax = rowmin + ( (rows - 1) / 8);
777 cout << " dumping region = " << colmin << "," << rowmin << " to " <<
778 colmax << "," << rowmax << "\n";
780 // generate the base directory
781 string base_path = p.gen_base_path();
782 cout << "fg_root = " << fg_root << " Base Path = " << base_path << endl;
783 dir = fg_root + "/Scenery/" + base_path;
784 cout << "Dir = " << dir << endl;
786 // stat() directory and create if needed
788 result = stat(dir.c_str(), &stat_buf);
789 if ( result != 0 && errno == ENOENT ) {
790 cout << "Creating directory\n";
794 command = "mkdir -p " + dir + "\n";
795 system( command.c_str() );
800 // Cygwin crashes when trying to output to node file
801 // explicitly making directory structure seems OK on Win95
803 extract_path (base_path, tmp_path);
805 dir = fg_root + "/Scenery";
806 if (my_mkdir ( dir.c_str() )) { exit (-1); }
808 dir = fg_root + "/Scenery/" + tmp_path;
809 if (my_mkdir ( dir.c_str() )) { exit (-1); }
811 dir = fg_root + "/Scenery/" + base_path;
812 if (my_mkdir ( dir.c_str() )) { exit (-1); }
818 // assume directory exists
821 // get index and generate output file name
822 index = p.gen_index();
823 sprintf(file, "%s/%ld.node", dir.c_str(), index);
825 // get (optional) extra node file name (in case there is matching
827 strcpy(exfile, file);
828 strcat(exfile, ".ex");
830 // load extra nodes if they exist
832 if ( (fd = fopen(exfile, "r")) != NULL ) {
834 fscanf(fd, "%d %d %d %d", &excount, &junki, &junki, &junki);
836 if ( excount > MAX_EX_NODES - 1 ) {
837 printf("Error, too many 'extra' nodes, increase array size\n");
840 printf(" Expecting %d 'extra' nodes\n", excount);
843 for ( i = 1; i <= excount; i++ ) {
844 fscanf(fd, "%d %lf %lf %lf\n", &junki,
845 &exnodes[i][0], &exnodes[i][1], &exnodes[i][2]);
846 printf("(extra) %d %.2f %.2f %.2f\n",
847 i, exnodes[i][0], exnodes[i][1], exnodes[i][2]);
852 printf("Creating node file: %s\n", file);
853 fd = fopen(file, "w");
855 // first count regular nodes to generate header
857 for ( j = rowmin; j <= rowmax; j++ ) {
858 for ( i = colmin; i <= colmax; i++ ) {
859 if ( output_data[i][j] > -9000.0 ) {
863 // printf(" count = %d\n", count);
865 fprintf(fd, "%d 2 1 0\n", count + excount);
867 // now write out extra node data
868 for ( i = 1; i <= excount; i++ ) {
869 fprintf(fd, "%d %.2f %.2f %.2f\n",
870 i, exnodes[i][0], exnodes[i][1], exnodes[i][2]);
873 // write out actual node data
875 for ( j = rowmin; j <= rowmax; j++ ) {
876 for ( i = colmin; i <= colmax; i++ ) {
877 if ( output_data[i][j] > -9000.0 ) {
878 fprintf(fd, "%d %.2f %.2f %.2f\n",
880 originx + (double)i * col_step,
881 originy + (double)j * row_step,
885 // printf(" count = %d\n", count);
893 FGDem::~FGDem( void ) {
894 // printf("class FGDem DEstructor called.\n");
896 delete [] output_data;
901 // Revision 1.25 1999/03/12 22:53:07 curt
902 // Added a routine to dump out the portion of the dem data covered by a
903 // specified bucket. Other changes related to needs of scenery tools overhaul.
905 // Revision 1.24 1999/03/11 23:31:56 curt
906 // Tweaks to use newbucket.hxx
908 // Revision 1.23 1999/03/10 01:09:12 curt
909 // Tweaks to go along with scenery tools overhaul.
910 // Added a new constructor that accepts the file name.
912 // Revision 1.22 1999/01/19 20:56:56 curt
913 // MacOS portability changes contributed by "Robert Puyol" <puyol@abvent.fr>
915 // Revision 1.21 1998/11/06 14:04:32 curt
916 // Changes due to updates in fgstream.
918 // Revision 1.20 1998/10/28 19:38:20 curt
919 // Elliminate some unnecessary win32 specific stuff (by Norman Vine)
921 // Revision 1.19 1998/10/22 21:59:19 curt
922 // Fixed a couple subtle bugs that resulted from some of my c++ conversions.
923 // One bug could cause a segfault on certain input, and the other bug could
924 // cause the whole procedure to go balistic and generate huge files (also only
925 // on rare input combinations.)
927 // Revision 1.18 1998/10/18 01:17:09 curt
930 // Revision 1.17 1998/10/16 19:08:12 curt
931 // Portability updates from Bernie Bright.
933 // Revision 1.16 1998/10/02 21:41:39 curt
936 // Revision 1.15 1998/09/21 20:53:59 curt
937 // minor tweaks to clean a few additional things up after the rewrite.
939 // Revision 1.14 1998/09/19 17:59:45 curt
940 // Use c++ streams (fg_gzifstream). Also converted many character arrays to
943 // Revision 1.13 1998/09/09 16:24:04 curt
944 // Fixed a bug in the handling of exclude files which was causing
945 // a crash by calling fclose() on an invalid file handle.
947 // Revision 1.12 1998/08/24 20:03:31 curt
948 // Eliminated a possible memory overrun error.
949 // Use the proper free() rather than the incorrect delete().
951 // Revision 1.11 1998/07/20 12:46:11 curt
952 // When outputing to a .node file, first check for an optional
953 // "index.node.ex" file in case there is a .poly file to go along with this
954 // node file. Include these nodes first since they are referenced by position
955 // from the .poly file. This is my first pass at adding an area "cutout"
956 // feature to the terrain generation pipeline.
958 // Revision 1.10 1998/07/13 20:58:02 curt
961 // Revision 1.9 1998/07/13 15:29:49 curt
962 // Added #ifdef HAVE_CONFIG_H
964 // Revision 1.8 1998/07/04 00:47:18 curt
965 // typedef'd struct fgBUCKET.
967 // Revision 1.7 1998/06/05 18:14:39 curt
968 // Abort out early when reading the "A" record if it doesn't look like
969 // a proper DEM file.
971 // Revision 1.6 1998/05/02 01:49:21 curt
972 // Fixed a bug where the wrong variable was being initialized.
974 // Revision 1.5 1998/04/25 15:00:32 curt
975 // Changed "r" to "rb" in gzopen() options. This fixes bad behavior in win32.
977 // Revision 1.4 1998/04/22 13:14:46 curt
978 // Fixed a bug in zlib usage.
980 // Revision 1.3 1998/04/18 03:53:05 curt
981 // Added zlib support.
983 // Revision 1.2 1998/04/14 02:43:27 curt
984 // Used "new" to auto-allocate large DEM parsing arrays in class constructor.
986 // Revision 1.1 1998/04/08 22:57:22 curt
987 // Adopted Gnu automake/autoconf system.
989 // Revision 1.3 1998/04/06 21:09:41 curt
990 // Additional win32 support.
991 // Fixed a bad bug in dem file parsing that was causing the output to be
992 // flipped about x = y.
994 // Revision 1.2 1998/03/23 20:35:41 curt
995 // Updated to use FG_EPSILON
997 // Revision 1.1 1998/03/19 02:54:47 curt
998 // Reorganized into a class lib called fgDEM.
1000 // Revision 1.1 1998/03/19 01:46:28 curt
1001 // Initial revision.