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/* utm2ll.c - convert Universal Transverse Mercator into latitude & longitude
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**
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** Partially based on code by Chuck Gantz <chuck.gantz@globalstar.com>.
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** 
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** Copyright ? 2001 by Jef Poskanzer <jef@acme.com>.
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** All rights reserved.
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**
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** Redistribution and use in source and binary forms, with or without
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** modification, are permitted provided that the following conditions
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** are met:
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** 1. Redistributions of source code must retain the above copyright
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**    notice, this list of conditions and the following disclaimer.
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** 2. Redistributions in binary form must reproduce the above copyright
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**    notice, this list of conditions and the following disclaimer in the
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**    documentation and/or other materials provided with the distribution.
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**
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** THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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** ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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** IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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** ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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** FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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** DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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** OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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** HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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** OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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** SUCH DAMAGE.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <math.h>
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#include "coords.h"
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#define ABS(x) ((x)>=0?(x):(-x))
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static char* argv0;
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static void usage( void );
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static void parse_error( char* argstr );
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static void fprintll( FILE* fp, char* fmt, double lat, double lng );
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int
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main( int argc, char** argv )
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    {
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    char* format = "%ns %Ad  %ew %Od";
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    int arglen, argn;
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    char* argstr;
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    double northing, easting;
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    int zone;
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    char letter[100];
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    double x, y;
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    double eccPrimeSquared;
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    double e1;
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    double N1, T1, C1, R1, D, M;
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    double long_origin;
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    double mu, phi1_rad;
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    int northernHemisphere;	/* 1 for northern hemisphere, 0 for southern */
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    double latitude, longitude;
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    argv0 = argv[0];
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    if ( argc >= 3 && strcmp( argv[1], "-f" ) == 0 )
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	{
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	format = argv[2];
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	argv += 2;
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	argc -= 2;
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	}
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    if ( argc < 2 )
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	usage();
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    /* Collect all args into a single string. */
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    arglen = 0;
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    for ( argn = 1; argn < argc; ++argn )
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	arglen += strlen( argv[argn] + 1 );
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    argstr = (char*) malloc( arglen );
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    if ( argstr == (char*) 0 )
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	{
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	(void) fprintf( stderr, "%s: out of memory\n", argv0 );
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	exit( 1 );
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	}
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    (void) strcpy( argstr, "" );
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    for ( argn = 1; argn < argc; ++argn )
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	{
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	if ( argn > 1 )
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	    (void) strcat( argstr, " " );
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	(void) strcat( argstr, argv[argn] );
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	}
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    /* Trim leading and trailing blanks. */
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    while ( argstr[0] == ' ' )
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	(void) strcpy( argstr, &(argstr[1]) );
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    while ( argstr[strlen(argstr)-1] == ' ' )
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	argstr[strlen(argstr)-1] = '\0';
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    /* Parse string into northing, easting, and zone. */
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    if ( sscanf( argstr, "%lf %lf %d%[A-Z]", &northing, &easting, &zone, letter ) == 4 )
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	;
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    else if ( sscanf( argstr, "%lf %lf %d", &northing, &easting, &zone ) == 3 )
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	(void) strcpy( letter, "S" );
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    else
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	parse_error( argstr );
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    /* Now convert. */
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    x = easting - 500000.0;	/* remove 500000 meter offset */
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    y = northing;
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    if ( ( *letter - 'N' ) >= 0 )
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	northernHemisphere = 1;	/* northern hemisphere */
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    else
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	{
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	northernHemisphere = 0;	/* southern hemisphere */
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	y -= 10000000.0;	/* remove 1e7 meter offset */
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	}
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    long_origin = ( zone - 1 ) * 6 - 180 + 3;	/* +3 puts origin in middle of zone */
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    eccPrimeSquared = EccentricitySquared / ( 1.0 - EccentricitySquared );
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    e1 = ( 1.0 - sqrt( 1.0 - EccentricitySquared ) ) / ( 1.0 + sqrt( 1.0 - EccentricitySquared ) );
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    M = y / K0;
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    mu = M / ( EquatorialRadius * ( 1.0 - EccentricitySquared / 4 - 3 * EccentricitySquared * EccentricitySquared / 64 - 5 * EccentricitySquared * EccentricitySquared * EccentricitySquared / 256 ) );
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    phi1_rad = mu + ( 3 * e1 / 2 - 27 * e1 * e1 * e1 / 32 )* sin( 2 * mu ) + ( 21 * e1 * e1 / 16 - 55 * e1 * e1 * e1 * e1 / 32 ) * sin( 4 * mu ) + ( 151 * e1 * e1 * e1 / 96 ) * sin( 6 *mu );
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    N1 = EquatorialRadius / sqrt( 1.0 - EccentricitySquared * sin( phi1_rad ) * sin( phi1_rad ) );
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    T1 = tan( phi1_rad ) * tan( phi1_rad );
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    C1 = eccPrimeSquared * cos( phi1_rad ) * cos( phi1_rad );
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    R1 = EquatorialRadius * ( 1.0 - EccentricitySquared ) / pow( 1.0 - EccentricitySquared * sin( phi1_rad ) * sin( phi1_rad ), 1.5 );
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    D = x / ( N1 * K0 );
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    latitude = phi1_rad - ( N1 * tan( phi1_rad ) / R1 ) * ( D * D / 2 -( 5 + 3 * T1 + 10 * C1 - 4 * C1 * C1 - 9 * eccPrimeSquared ) * D * D * D * D / 24 + ( 61 + 90 * T1 + 298 * C1 + 45 * T1 * T1 - 252 * eccPrimeSquared - 3 * C1 * C1 ) * D * D * D * D * D * D / 720 );
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    latitude = latitude * 180.0 / M_PI;
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    longitude = ( D - ( 1 + 2 * T1 + C1 ) * D * D * D / 6 + ( 5 - 2 * C1 + 28 * T1 - 3 * C1 * C1 + 8 * eccPrimeSquared + 24 * T1 * T1 ) * D * D * D * D * D / 120 ) / cos( phi1_rad );
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    longitude = long_origin + longitude * 180.0 / M_PI;
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    /* Show results. */
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    fprintll( stdout, format, latitude, longitude );
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    putchar( '\n' );
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    /* All done. */
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    exit( 0 );
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    }
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static void
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usage( void )
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    {
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    (void) fprintf( stderr, "usage:  %s [-f format] UTM\n", argv0 );
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    exit( 1 );
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    }
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static void
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parse_error( char* argstr )
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    {
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    (void) fprintf(
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	stderr, "%s: can't parse UTM coordinates '%s'\n", argv0, argstr );
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    exit( 1 );
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    }
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static void
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fprintll( FILE* fp, char* fmt, double lat, double lng )
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    {
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    char ns = lat >= 0.0 ? 'N' : 'S';
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    char ew = lng >= 0.0 ? 'E' : 'W';
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    double abs_lat = ABS( lat );
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    double abs_lng = ABS( lng );
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    int int_deg_lat = (int) lat;
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    int int_deg_lng = (int) lng;
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    int int_abs_deg_lat = ABS( int_deg_lat );
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    int int_abs_deg_lng = ABS( int_deg_lng );
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    double min_lat = ( abs_lat - int_abs_deg_lat ) * 60;
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    double min_lng = ( abs_lng - int_abs_deg_lng ) * 60;
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    int int_min_lat = (int) min_lat;
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    int int_min_lng = (int) min_lng;
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    double sec_lat = ( min_lat - int_min_lat ) * 60;
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    double sec_lng = ( min_lng - int_min_lng ) * 60;
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    int int_sec_lat = (int) sec_lat;
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    int int_sec_lng = (int) sec_lng;
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    char* cp;
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    char c1, c2;
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    for ( cp = fmt; *cp != '\0'; ++cp )
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	{
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	if ( *cp != '%' )
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	    {
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	    putc( *cp, fp );
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	    continue;
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	    }
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	++cp;
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	if ( *cp == '\0' )
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	    {
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	    putc( '%', fp );
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	    break;
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	    }
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	if ( *cp == '%' )
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	    {
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	    putc( '%', fp );
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	    continue;
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	    }
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	c1 = *cp;
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	++cp;
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	if ( *cp == '\0' )
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	    {
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	    putc( '%', fp );
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	    putc( c1, fp );
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	    break;
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	    }
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	c2 = *cp;
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	if ( c1 == 'n' && c2 == 's' )
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	    putc( ns, fp );
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	else if ( c1 == 'e' && c2 == 'w' )
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	    putc( ew, fp );
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	else if ( c1 == 'a' && c2 == 'd' )
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	    (void) fprintf( fp, "%0.8g", lat );
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	else if ( c1 == 'o' && c2 == 'd' )
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	    (void) fprintf( fp, "%0.8g", lng );
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	else if ( c1 == 'A' && c2 == 'd' )
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	    (void) fprintf( fp, "%0.8g", abs_lat );
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	else if ( c1 == 'O' && c2 == 'd' )
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	    (void) fprintf( fp, "%0.8g", abs_lng );
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	else if ( c1 == 'a' && c2 == 'D' )
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	    (void) fprintf( fp, "%d", int_deg_lat );
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	else if ( c1 == 'o' && c2 == 'D' )
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	    (void) fprintf( fp, "%d", int_deg_lng );
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	else if ( c1 == 'A' && c2 == 'D' )
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	    (void) fprintf( fp, "%d", int_abs_deg_lat );
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	else if ( c1 == 'O' && c2 == 'D' )
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	    (void) fprintf( fp, "%d", int_abs_deg_lng );
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	else if ( c1 == 'a' && c2 == 'm' )
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	    (void) fprintf( fp, "%0.6g", min_lat );
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	else if ( c1 == 'o' && c2 == 'm' )
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	    (void) fprintf( fp, "%0.6g", min_lng );
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	else if ( c1 == 'a' && c2 == 'M' )
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	    (void) fprintf( fp, "%d", int_min_lat );
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	else if ( c1 == 'o' && c2 == 'M' )
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	    (void) fprintf( fp, "%d", int_min_lng );
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	else if ( c1 == 'a' && c2 == 's' )
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	    (void) fprintf( fp, "%0.4g", sec_lat );
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	else if ( c1 == 'o' && c2 == 's' )
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	    (void) fprintf( fp, "%0.4g", sec_lng );
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	else if ( c1 == 'a' && c2 == 'S' )
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	    (void) fprintf( fp, "%d", int_sec_lat );
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	else if ( c1 == 'o' && c2 == 'S' )
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	    (void) fprintf( fp, "%d", int_sec_lng );
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	else
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	    {
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	    putc( '%', fp );
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	    putc( c1, fp );
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	    putc( c2, fp );
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	    }
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	}
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    }
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