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/****************************************************************************/
/* */
/* ./grid/utm.c - Convert to and from UTM Grid Format */
/* */
/* This file is part of gpstrans - a program to communicate with garmin gps */
/* Parts are taken from John F. Waers (jfwaers@csn.net) program MacGPS. */
/* */
/* */
/* Copyright (c) 1995 by Carsten Tschach (tschach@zedat.fu-berlin.de) */
/* */
/* Permission to use, copy, modify, and distribute this software and its */
/* documentation for non-commercial purpose, is hereby granted without fee, */
/* providing that the copyright notice appear in all copies and that both */
/* the copyright notice and this permission notice appear in supporting */
/* documentation. I make no representations about the suitability of this */
/* software for any purpose. It is provides "as is" without express or */
/* implid warranty. */
/* */
/****************************************************************************/
#include "defs.h"
#include "Garmin.h"
#include <math.h>
/* define constants */
static const double lat0 = 0.0; /* reference transverse mercator latitude */
static const double k0 = 0.9996;
/****************************************************************************/
/* Convert degree to UTM Grid. */
/****************************************************************************/
void DegToUTM(double lat, double lon, char *zone, double *x, double *y)
{
char nz;
double lon0;
if ((lat >= -80.0) && (lat <= 84.0)) {
nz = 'C'+((short)(lat + 80.0)) / 8;
/* skip 'I' and 'O' */
if (nz > 'H') ++nz;
if (nz > 'N') ++nz;
lon0 = 6.0 * (double) ((int) (lon / 6.0)) + 3.0;
sprintf(zone, "%02d\t%c", ((short)lon0 +183) / 6, nz);
toTM(lat, lon, lat0, lon0, k0, x, y);
/* false easting */
*x = *x + 500000.0;
/* false northing for southern hemisphere */
if (lat < 0.0) *y = 10000000.0 - *y;
} else {
strcpy(zone, "00\tx");
if (lat > 0.0)
if (lon < 0.0) zone[3] = 'Y';
else zone[3] = 'Z';
else
if (lon < 0.0) zone[3] = 'A';
else zone[3] = 'B';
toUPS(lat, lon, x, y);
}
}
/****************************************************************************/
/* Convert UTM Grid to degree. */
/****************************************************************************/
void UTMtoDeg(short zone, short southernHemisphere, double x, double y,
double *lat, double *lon)
{
double lon0;
if (zone != 0) {
lon0 = (double)((-183 + 6 * zone));
/* remove false northing for southern hemisphere and false easting */
if (southernHemisphere)
y = 1.0e7 - y;
x -= 500000.0;
fromTM(x, y, lat0, lon0, k0, lat, lon);
} else
fromUPS(southernHemisphere, x, y, lat, lon);
}
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