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int usage(int retval, bool brief) {
if (brief)
( retval ? std::cerr : std::cout ) << "Usage:\n"
" IntersectTool [ -c | -n | -i | -o | [ -R maxdist ] [ -e a f] [ -E ] [\n"
" -w ] [ -p prec ] [ --comment-delimiter commentdelim ] [ --version | -h\n"
" | --help ] [ --input-file infile | --input-string instring ] [\n"
" --line-separator linesep ] [ --output-file outfile ]\n"
"\n"
"For full documentation type:\n"
" IntersectTool --help\n"
"or visit:\n"
" https://geographiclib.sourceforge.io/C++/2.6/IntersectTool.1.html\n";
else
( retval ? std::cerr : std::cout ) << "Man page:\n"
"\n"
"SYNOPSIS\n"
" IntersectTool [ -c | -n | -i | -o | [ -R maxdist ] [ -e a f] [ -E ] [\n"
" -w ] [ -p prec ] [ --comment-delimiter commentdelim ] [ --version | -h\n"
" | --help ] [ --input-file infile | --input-string instring ] [\n"
" --line-separator linesep ] [ --output-file outfile ]\n"
"\n"
"DESCRIPTION\n"
" IntersectTool finds the intersection of two geodesics X and Y. The\n"
" geodesics may either be specified as a location and an azimuth, latX\n"
" lonX aziX, or as the shortest geodesic segment between two locations,\n"
" latX1 lonX1 and latX2 lonX2. The intersection is then specified as the\n"
" displacements, x and y, along the geodesics X and Y from the starting\n"
" points to the intersection. In the case of the intersection of\n"
" geodesic segments, the starting point is first point specified for X or\n"
" Y.\n"
"\n"
" Usually this tool returns the closest intersection defined as the one\n"
" that minimizes the \"L1\" distance, |x| + |y|. However, it is possible\n"
" to specify an \"origin\" x0 and y0 when determining closeness so that the\n"
" intersection which minimizes |x - x0| + |y - y0| is returned.\n"
"\n"
" In the case of intersecting segments the origin is taken to be the\n"
" midpoints of the segments; x0 is half the distance from X1 to X2. In\n"
" addition a flag is returned specifying whether the intersection is\n"
" \"within\" the segments.\n"
"\n"
" The tool also returns a \"coincidence indicator\" c. This is typically\n"
" 0. However if the geodesics lie on top of one another at the point of\n"
" intersection, then c is set to 1, if they are parallel, and -1, if they\n"
" are antiparallel.\n"
"\n"
" IntersectTool operates in one of three modes:\n"
"\n"
" 1. With the -c option (the default), IntersectTool accepts lines on\n"
" the standard input containing latX lonX aziX latY lonY aziY,\n"
" specifying two geodesic lines X and Y, and prints the location of\n"
" the closest intersection x y c on standard output.\n"
"\n"
" 2. With the -n option, IntersectTool accepts lines on the standard\n"
" input containing latX lonX aziX aziY aziY, specifying a point where\n"
" two geodesic lines X and Y intersect, and prints the location of\n"
" the next closest intersection x y c on standard output.\n"
"\n"
" 3. With the -i option, IntersectTool accepts lines on the standard\n"
" input containing latX1 lonX1 latX2 lonX2 latY1 lonY1 latY2 lonY2,\n"
" specifying two geodesic segments X1-X2 and Y1-Y2, and prints x y c\n"
" k on standard output. Here k is a flag in [-4,4] specifying\n"
" whether the intersection is within the segments (0) or not\n"
" (non-zero). x and y give the distances from X1 and Y1\n"
" respectively. k is set to 3 kx + ky where kx = -1 if x < 0, 0 if 0\n"
" <= x <= sx, 1 if sx < x, and similarly for ky; sx is the length of\n"
" the segment X1-X2.\n"
"\n"
" 4. With the -o option, IntersectTool accepts lines on the standard\n"
" input containing latX lonX aziX latY lonY aziY x0 y0, specifying\n"
" two geodesic lines X and Y and two offsets, and prints x y c on\n"
" standard output where [x, y] is the intersection closest to [x0,\n"
" y0].\n"
"\n"
"OPTIONS\n"
" -c find the closest intersection (see 1 above).\n"
"\n"
" -n find the intersection closest to a given intersection (see 2\n"
" above).\n"
"\n"
" -i find the intersection of two geodesic segments (see 3 above).\n"
"\n"
" -o find the closest intersection with an offset.\n"
"\n"
" -R maxdist\n"
" modifies the four modes to return all the intersections within an\n"
" L1 distance, maxdist, of the relevant origin: [0, 0] for -c and -n,\n"
" the midpoints of the segments for -i, and [x0, y0] for -o. For\n"
" each intersection, x y c z is printed on standard output. Here z\n"
" is the L1 distance of the intersection from the origin and the\n"
" intersections are sorted by the distances. A line \"nan nan 0 nan\"\n"
" is added after the intersections, so that the output can be\n"
" associated with the correct lines of the input. The number of\n"
" intersections scales as (maxdist/(pi a))^2.\n"
"\n"
" -C check the intersections. For each computed intersection, print on\n"
" standard error a line latX lonX latY lonY sXY giving the computed\n"
" positions of the intersections points on X and Y and the distance\n"
" between them. If -w is specified, the longitude is given before\n"
" the latitude.\n"
"\n"
" -e a f\n"
" specify the ellipsoid via the equatorial radius, a and the\n"
" flattening, f. Setting f = 0 results in a sphere. Specify f < 0\n"
" for a prolate ellipsoid. A simple fraction, e.g., 1/297, is\n"
" allowed for f. By default, the WGS84 ellipsoid is used, a =\n"
" 6378137 m, f = 1/298.257223563.\n"
"\n"
" -E use \"exact\" algorithms (based on elliptic integrals) for the\n"
" geodesic calculations. These are more accurate than the (default)\n"
" series expansions for |f| > 0.02.\n"
"\n"
" -w on input, longitude precedes latitude (except that on input this\n"
" can be overridden by a hemisphere designator, N, S, E, W).\n"
"\n"
" -p prec\n"
" set the output precision to prec (default 3); prec is the precision\n"
" relative to 1 m. See \"PRECISION\".\n"
"\n"
" --comment-delimiter commentdelim\n"
" set the comment delimiter to commentdelim (e.g., \"#\" or \"//\"). If\n"
" set, the input lines will be scanned for this delimiter and, if\n"
" found, the delimiter and the rest of the line will be removed prior\n"
" to processing and subsequently appended to the output line\n"
" (separated by a space).\n"
"\n"
" --version\n"
" print version and exit.\n"
"\n"
" -h print usage and exit.\n"
"\n"
" --help\n"
" print full documentation and exit.\n"
"\n"
" --input-file infile\n"
" read input from the file infile instead of from standard input; a\n"
" file name of \"-\" stands for standard input.\n"
"\n"
" --input-string instring\n"
" read input from the string instring instead of from standard input.\n"
" All occurrences of the line separator character (default is a\n"
" semicolon) in instring are converted to newlines before the reading\n"
" begins.\n"
"\n"
" --line-separator linesep\n"
" set the line separator character to linesep. By default this is a\n"
" semicolon.\n"
"\n"
" --output-file outfile\n"
" write output to the file outfile instead of to standard output; a\n"
" file name of \"-\" stands for standard output.\n"
"\n"
"INPUT\n"
" IntersectTool measures all angles in degrees and all lengths in meters.\n"
" On input angles (latitude, longitude, azimuth) can be as decimal\n"
" degrees or degrees, minutes, seconds. For example, \"40d30\", \"40d30'\",\n"
" \"40:30\", \"40.5d\", and 40.5 are all equivalent. By default, latitude\n"
" precedes longitude for each point (the -w flag switches this\n"
" convention); however either may be given first by appending (or\n"
" prepending) N or S to the latitude and E or W to the longitude.\n"
" Azimuths are measured clockwise from north; however this may be\n"
" overridden with E or W.\n"
"\n"
" For details on the allowed formats for angles, see the \"GEOGRAPHIC\n"
" COORDINATES\" section of GeoConvert(1).\n"
"\n"
"PRECISION\n"
" prec gives precision of the output with prec = 0 giving 1 m precision,\n"
" prec = 3 giving 1 mm precision, etc. prec is the number of digits\n"
" after the decimal point for lengths. The latitude and longitude\n"
" printed to standard error with the -C option are given in decimal\n"
" degrees with prec + 5 digits after the decimal point. The minimum\n"
" value of prec is 0 and the maximum is 10.\n"
"\n"
"ERRORS\n"
" An illegal line of input will print an error message to standard output\n"
" beginning with \"ERROR:\" and causes IntersectTool to return an exit code\n"
" of 1. However, an error does not cause IntersectTool to terminate;\n"
" following lines will be converted.\n"
"\n"
"ACCURACY\n"
" This tool will give nearly full double precision accuracy for |f| <\n"
" 0.02. If the -E option is given, full accuracy is achieved for -1/4 <\n"
" f < 1/5. The tool had not been tested outside this range.\n"
"\n"
"EXAMPLES\n"
" A vessel leaves Plymouth 50N 4W on a geodesic path with initial heading\n"
" 147.7W. When will it first cross the equator?\n"
"\n"
" echo 50N 4W 147.7W 0 0 90 | IntersectTool -c -p 0 -C\n"
"\n"
" 6058049 -3311253 0\n"
" 0.00000 -29.74549 -0.00000 -29.74549 0\n"
"\n"
" Answer: after 6058km at longitude 29.7W. When will it cross the date\n"
" line, longitude 180E? Here we need to use -R because there a closer\n"
" intersection on the prime meridian:\n"
"\n"
" echo 50N 4W 147.7W 0 180 0 | IntersectTool -c -p 0 -C -R 2.6e7\n"
"\n"
" -494582 14052230 0 14546812\n"
" 53.69260 0.00000 53.69260 0.00000 0\n"
" 19529110 -5932344 0 25461454\n"
" -53.51867 180.00000 -53.51867 180.00000 0\n"
" nan nan 0 nan\n"
" nan nan nan nan nan\n"
"\n"
" We want the second result: after 19529 km at latitude 53.5S.\n"
"\n"
"SEE ALSO\n"
" GeoConvert(1), GeodSolve(1).\n"
"\n"
" This solution for intersections is described in C. F. F. Karney,\n"
" Geodesic intersections, J. Surveying Eng. 150(3), 04024005:1-9 (2024),\n"
" DOI: <https://doi.org/10.1061/JSUED2.SUENG-1483>; preprint\n"
" <https://arxiv.org/abs/2308.00495>. It is based on the work of S.\n"
" Baseldga and J. C. Martinez-Llario, Intersection and point-to-line\n"
" solutions for geodesics on the ellipsoid, Stud. Geophys. Geod. 62,\n"
" 353-363 (2018); DOI: <https://doi.org/10.1007/s11200-017-1020-z>;\n"
"\n"
"AUTHOR\n"
" IntersectTool was written by Charles Karney.\n"
"\n"
"HISTORY\n"
;
return retval;
}
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