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/****************************************************************************/
/* */
/* ./gps/dms.c - Convert to various position formats */
/* */
/* 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>
/****************************************************************************/
/* The reference latitude and k0 factor were determined empirically to fit */
/* the GPS data. */
/****************************************************************************/
/* define constants */
static const char *zoneID = "VWXYZQRSTULMNOPFGHJKABCDE";
static const double lat0 = 53.4999886; /* reference transverse mercator */
static const double lon0 = -8.0; /* latitude and longitude */
static const double k0 = 1.000035;
/****************************************************************************/
/* Convert degree to Irish Grid Format. */
/****************************************************************************/
void DegToITM(double lat, double lon, char *zone, double *x, double *y)
{
short X, Y;
strcpy(zone, "--");
toTM(lat, lon, lat0, lon0, k0, x, y);
/* add false easting and northing and round to nearest meter */
*x = floor(*x + 200000.0 + 0.5);
*y = floor(*y + 250000.0 + 0.5);
/* check for invalid range */
if (*x < 0.0 || *x >500000.0 || *y < 0.0 || *y > 500000.0) {
/* return with zone = "--" and set x and y to 0.0 */
*x = 0.0;
*y = 0.0;
return;
}
X = (long)*x / 100000;
Y = (long)*y / 100000;
*x = (long)*x % 100000;
*y = (long)*y % 100000;
zone[0] = 'I';
zone[1] = zoneID[5 * Y + X];
}
/****************************************************************************/
/* Convert Irish Grid Format to degree. */
/****************************************************************************/
void ITMtoDeg(char *zone, double x, double y, double *lat, double *lon)
{
int n;
/* Check for invalid zone */
if (strcmp(zone, "--") == 0 || x < 0.0 || x > 100000.0 || y < 0.0 ||
y > 100000.0) {
*lat = 0.0;
*lon = 0.0;
return;
}
n = strchr(zoneID, zone[1]) - zoneID;
x += (n % 5) * 100000.0 - 200000.0;
y += (n / 5) * 100000.0 - 250000.0;
fromTM(x, y, lat0, lon0, k0, lat, lon);
}
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