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Hamlib/src/locator.c

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/**
* \addtogroup utilities
* @{
*/
/**
* \file src/locator.c
* \brief locator and bearing conversion interface
* \author Stephane Fillod and the Hamlib Group
* \date 2000-2010
*
* Hamlib Interface - locator, bearing, and conversion calls
*/
/*
* Hamlib Interface - locator and bearing conversion calls
* Copyright (c) 2001-2010 by Stephane Fillod
* Copyright (c) 2003 by Nate Bargmann
* Copyright (c) 2003 by Dave Hines
*
*
* Code to determine bearing and range was taken from the Great Circle,
* by S. R. Sampson, N5OWK.
* Ref: "Air Navigation", Air Force Manual 51-40, 1 February 1987
* Ref: "ARRL Satellite Experimenters Handbook", August 1990
*
* Code to calculate distance and azimuth between two Maidenhead locators,
* taken from wwl, by IK0ZSN Mirko Caserta.
*
* New bearing code added by N0NB was found at:
* http://williams.best.vwh.net/avform.htm#Crs
*
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
/*! \page hamlib Hamlib general purpose API
*
* Here are grouped some often used functions, like locator conversion
* routines.
*/
#ifdef HAVE_CONFIG_H
# include "config.h"
#endif
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <math.h>
#include <hamlib/rotator.h>
#ifndef DOC_HIDDEN
#define RADIAN (180.0 / M_PI)
/* arc length for 1 degree, 60 Nautical Miles */
#define ARC_IN_KM 111.2
/* The following is contributed by Dave Hines M1CXW
*
* begin dph
*/
/*
* These are the constants used when converting between Maidenhead grid
* locators and longitude/latitude values. MAX_LOCATOR_PAIRS is the maximum
* number of locator character pairs to convert. This number MUST NOT exceed
* the number of pairs of values in loc_char_range[].
* Setting MAX_LOCATOR_PAIRS to 3 will convert the currently defined 6
* character locators. A value of 4 will convert the extended 8 character
* locators described in section 3L of "The IARU region 1 VHF managers
* handbook". Values of 5 and 6 will extent the format even more, to the
* longest definition I have seen for locators, see
* http://www.btinternet.com/~g8yoa/geog/non-ra.html
* Beware that there seems to be no universally accepted standard for 10 & 12
* character locators.
*
* The ranges of characters which will be accepted by locator2longlat, and
* generated by longlat2locator, are specified by the loc_char_range[] array.
* This array may be changed without requiring any other code changes.
*
* For the fifth pair to range from aa to xx use:
* const static int loc_char_range[] = { 18, 10, 24, 10, 24, 10 };
*
* For the fifth pair to range from aa to yy use:
* const static int loc_char_range[] = { 18, 10, 24, 10, 25, 10 };
*
* MAX_LOCATOR_PAIRS now sets the limit locator2longlat() will convert and
* sets the maximum length longlat2locator() will generate. Each function
* properly handles any value from 1 to 6 so MAX_LOCATOR_PAIRS should be
* left at 6. MIN_LOCATOR_PAIRS sets a floor on the shortest locator that
* should be handled. -N0NB
*/
const static int loc_char_range[] = { 18, 10, 24, 10, 24, 10 };
#define MAX_LOCATOR_PAIRS 6
#define MIN_LOCATOR_PAIRS 1
/* end dph */
#endif /* !DOC_HIDDEN */
/**
* \brief Convert DMS to decimal degrees
* \param degrees Degrees, whole degrees
* \param minutes Minutes, whole minutes
* \param seconds Seconds, decimal seconds
* \param sw South or West
*
* Convert degree/minute/second angle to decimal degrees angle.
* \a degrees >360, \a minutes > 60, and \a seconds > 60.0 are allowed,
* but resulting angle won't be normalized.
*
* When the variable sw is passed a value of 1, the returned decimal
* degrees value will be negative (south or west). When passed a
* value of 0 the returned decimal degrees value will be positive
* (north or east).
*
* \return The angle in decimal degrees.
*
* \sa dec2dms()
*/
double HAMLIB_API dms2dec(int degrees, int minutes, double seconds, int sw)
{
double st;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
if (degrees < 0)
{
degrees = abs(degrees);
}
if (minutes < 0)
{
minutes = abs(minutes);
}
if (seconds < 0)
{
seconds = fabs(seconds);
}
st = (double)degrees + (double)minutes / 60. + seconds / 3600.;
if (sw == 1)
{
return -st;
}
else
{
return st;
}
}
/**
* \brief Convert D M.MMM notation to decimal degrees
* \param degrees Degrees, whole degrees
* \param minutes Minutes, decimal minutes
* \param sw South or West
*
* Convert a degrees, decimal minutes notation common on
* many GPS units to its decimal degrees value.
*
* \a degrees > 360, \a minutes > 60.0 are allowed, but
* resulting angle won't be normalized.
*
* When the variable sw is passed a value of 1, the returned decimal
* degrees value will be negative (south or west). When passed a
* value of 0 the returned decimal degrees value will be positive
* (north or east).
*
* \return The angle in decimal degrees.
*
* \sa dec2dmmm()
*/
double HAMLIB_API dmmm2dec(int degrees, double minutes, int sw)
{
double st;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
if (degrees < 0)
{
degrees = abs(degrees);
}
if (minutes < 0)
{
minutes = fabs(minutes);
}
st = (double)degrees + minutes / 60.;
if (sw == 1)
{
return -st;
}
else
{
return st;
}
}
/**
* \brief Convert decimal degrees angle into DMS notation
* \param dec Decimal degrees
* \param degrees Pointer for the calculated whole Degrees
* \param minutes Pointer for the calculated whole Minutes
* \param seconds Pointer for the calculated decimal Seconds
* \param sw Pointer for the calculated SW flag
*
* Convert decimal degrees angle into its degree/minute/second
* notation.
*
* When \a dec < -180 or \a dec > 180, the angle will be normalized
* within these limits and the sign set appropriately.
*
* Upon return dec2dms guarantees 0 >= \a degrees <= 180,
* 0 >= \a minutes < 60, and 0.0 >= \a seconds < 60.0.
*
* When \a dec is < 0.0 \a sw will be set to 1. When \a dec is
* >= 0.0 \a sw will be set to 0. This flag allows the application
* to determine whether the DMS angle should be treated as negative
* (south or west).
*
* \retval -RIG_EINVAL if any of the pointers are NULL.
* \retval RIG_OK if conversion went OK.
*
* \sa dms2dec()
*/
int HAMLIB_API dec2dms(double dec,
int *degrees,
int *minutes,
double *seconds,
int *sw)
{
int deg, min;
double st;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
/* bail if NULL pointers passed */
if (!degrees || !minutes || !seconds || !sw)
{
return -RIG_EINVAL;
}
/* reverse the sign if dec has a magnitude greater
* than 180 and factor out multiples of 360.
* e.g. when passed 270 st will be set to -90
* and when passed -270 st will be set to 90. If
* passed 361 st will be set to 1, etc. If passed
* a value > -180 || < 180, value will be unchanged.
*/
if (dec >= 0.0)
{
st = fmod(dec + 180, 360) - 180;
}
else
{
st = fmod(dec - 180, 360) + 180;
}
/* if after all of that st is negative, we want deg
* to be negative as well except for 180 which we want
* to be positive.
*/
if (st < 0.0 && st != -180)
{
*sw = 1;
}
else
{
*sw = 0;
}
/* work on st as a positive value to remove a
* bug introduced by the effect of floor() when
* passed a negative value. e.g. when passed
* -96.8333 floor() returns -95! Also avoids
* a rounding error introduced on negative values.
*/
st = fabs(st);
deg = (int)floor(st);
st = 60. * (st - (double)deg);
min = (int)floor(st);
st = 60. * (st - (double)min);
*degrees = deg;
*minutes = min;
*seconds = st;
return RIG_OK;
}
/**
* \brief Convert a decimal angle into D M.MMM notation
* \param dec Decimal degrees
* \param degrees Pointer for the calculated whole Degrees
* \param minutes Pointer for the calculated decimal Minutes
* \param sw Pointer for the calculated SW flag
*
* Convert a decimal angle into its degree, decimal minute
* notation common on many GPS units.
*
* When passed a value < -180 or > 180, the value will be normalized
* within these limits and the sign set apropriately.
*
* Upon return dec2dmmm guarantees 0 >= \a degrees <= 180,
* 0.0 >= \a minutes < 60.0.
*
* When \a dec is < 0.0 \a sw will be set to 1. When \a dec is
* >= 0.0 \a sw will be set to 0. This flag allows the application
* to determine whether the D M.MMM angle should be treated as negative
* (south or west).
*
* \retval -RIG_EINVAL if any of the pointers are NULL.
* \retval RIG_OK if conversion went OK.
*
* \sa dmmm2dec()
*/
int HAMLIB_API dec2dmmm(double dec, int *degrees, double *minutes, int *sw)
{
int r, min;
double sec;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
/* bail if NULL pointers passed */
if (!degrees || !minutes || !sw)
{
return -RIG_EINVAL;
}
r = dec2dms(dec, degrees, &min, &sec, sw);
if (r != RIG_OK)
{
return r;
}
*minutes = (double)min + sec / 60;
return RIG_OK;
}
/**
* \brief Convert Maidenhead grid locator to Longitude/Latitude
* \param longitude Pointer for the calculated Longitude
* \param latitude Pointer for the calculated Latitude
* \param locator The Maidenhead grid locator--2 through 12 char + nul string
*
* Convert Maidenhead grid locator to Longitude/Latitude (decimal degrees).
* The locator should be in 2 through 12 chars long format.
* \a locator2longlat is case insensitive, however it checks for
* locator validity.
*
* Decimal long/lat is computed to center of grid square, i.e. given
* EM19 will return coordinates equivalent to the southwest corner
* of EM19mm.
*
* \retval -RIG_EINVAL if locator exceeds RR99xx99xx99 or exceeds length
* limit--currently 1 to 6 lon/lat pairs.
* \retval RIG_OK if conversion went OK.
*
* \bug The fifth pair ranges from aa to xx, there is another convention
* that ranges from aa to yy. At some point both conventions should be
* supported.
*
* \sa longlat2locator()
*/
/* begin dph */
int HAMLIB_API locator2longlat(double *longitude,
double *latitude,
const char *locator)
{
int x_or_y, paircount;
int locvalue, pair;
int divisions;
double xy[2], ordinate;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
/* bail if NULL pointers passed */
if (!longitude || !latitude)
{
return -RIG_EINVAL;
}
paircount = strlen(locator) / 2;
/* verify paircount is within limits */
if (paircount > MAX_LOCATOR_PAIRS)
{
paircount = MAX_LOCATOR_PAIRS;
}
else if (paircount < MIN_LOCATOR_PAIRS)
{
return -RIG_EINVAL;
}
/* For x(=longitude) and y(=latitude) */
for (x_or_y = 0; x_or_y < 2; ++x_or_y)
{
ordinate = -90.0;
divisions = 1;
for (pair = 0; pair < paircount; ++pair)
{
locvalue = locator[pair * 2 + x_or_y];
/* Value of digit or letter */
locvalue -= (loc_char_range[pair] == 10) ? '0' :
(isupper(locvalue)) ? 'A' : 'a';
/* Check range for non-letter/digit or out of range */
if ((locvalue < 0) || (locvalue >= loc_char_range[pair]))
{
return -RIG_EINVAL;
}
divisions *= loc_char_range[pair];
ordinate += locvalue * 180.0 / divisions;
}
/* Center ordinate in the Maidenhead "square" or "subsquare" */
ordinate += 90.0 / divisions;
xy[x_or_y] = ordinate;
}
*longitude = xy[0] * 2.0;
*latitude = xy[1];
return RIG_OK;
}
/* end dph */
/**
* \brief Convert longitude/latitude to Maidenhead grid locator
* \param longitude Longitude, decimal degrees
* \param latitude Latitude, decimal degrees
* \param locator Pointer for the Maidenhead Locator
* \param pair_count Precision expressed as lon/lat pairs in the locator
*
* Convert longitude/latitude (decimal degrees) to Maidenhead grid locator.
* \a locator must point to an array at least \a pair_count * 2 char + '\\0'.
*
* \retval -RIG_EINVAL if \a locator is NULL or \a pair_count exceeds
* length limit. Currently 1 to 6 lon/lat pairs.
* \retval RIG_OK if conversion went OK.
*
* \bug \a locator is not tested for overflow.
* \bug The fifth pair ranges from aa to yy, there is another convention
* that ranges from aa to xx. At some point both conventions should be
* supported.
*
* \sa locator2longlat()
*/
/* begin dph */
int HAMLIB_API longlat2locator(double longitude,
double latitude,
char *locator,
int pair_count)
{
int x_or_y, pair, locvalue, divisions;
double square_size, ordinate;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
if (!locator)
{
return -RIG_EINVAL;
}
if (pair_count < MIN_LOCATOR_PAIRS || pair_count > MAX_LOCATOR_PAIRS)
{
return -RIG_EINVAL;
}
for (x_or_y = 0; x_or_y < 2; ++x_or_y)
{
ordinate = (x_or_y == 0) ? longitude / 2.0 : latitude;
divisions = 1;
/* The 1e-6 here guards against floating point rounding errors */
ordinate = fmod(ordinate + 270.000001, 180.0);
for (pair = 0; pair < pair_count; ++pair)
{
divisions *= loc_char_range[pair];
square_size = 180.0 / divisions;
locvalue = (int)(ordinate / square_size);
ordinate -= square_size * locvalue;
locvalue += (loc_char_range[pair] == 10) ? '0' : 'A';
locator[pair * 2 + x_or_y] = locvalue;
}
}
locator[pair_count * 2] = '\0';
return RIG_OK;
}
/* end dph */
/**
* \brief Calculate the distance and bearing between two points.
* \param lon1 The local Longitude, decimal degrees
* \param lat1 The local Latitude, decimal degrees
* \param lon2 The remote Longitude, decimal degrees
* \param lat2 The remote Latitude, decimal degrees
* \param distance Pointer for the distance, km
* \param azimuth Pointer for the bearing, decimal degrees
*
* Calculate the QRB between \a lon1, \a lat1 and \a lon2, \a lat2.
*
* This version will calculate the QRB to a precision sufficient
* for 12 character locators. Antipodal points, which are easily
* calculated, are considered equidistant and the bearing is
* simply resolved to be true north (0.0<EFBFBD>).
*
* \retval -RIG_EINVAL if NULL pointer passed or lat and lon values
* exceed -90 to 90 or -180 to 180.
* \retval RIG_OK if calculations are successful.
*
* \return The distance in kilometers and azimuth in decimal degrees
* for the short path are stored in \a distance and \a azimuth.
*
* \sa distance_long_path(), azimuth_long_path()
*/
int HAMLIB_API qrb(double lon1,
double lat1,
double lon2,
double lat2,
double *distance,
double *azimuth)
{
double delta_long, tmp, arc, az;
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
/* bail if NULL pointers passed */
if (!distance || !azimuth)
{
return -RIG_EINVAL;
}
if ((lat1 > 90.0 || lat1 < -90.0) || (lat2 > 90.0 || lat2 < -90.0))
{
return -RIG_EINVAL;
}
if ((lon1 > 180.0 || lon1 < -180.0) || (lon2 > 180.0 || lon2 < -180.0))
{
return -RIG_EINVAL;
}
/* Prevent ACOS() Domain Error */
if (lat1 == 90.0)
{
lat1 = 89.999999999;
}
else if (lat1 == -90.0)
{
lat1 = -89.999999999;
}
if (lat2 == 90.0)
{
lat2 = 89.999999999;
}
else if (lat2 == -90.0)
{
lat2 = -89.999999999;
}
/* Convert variables to Radians */
lat1 /= RADIAN;
lon1 /= RADIAN;
lat2 /= RADIAN;
lon2 /= RADIAN;
delta_long = lon2 - lon1;
tmp = sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(delta_long);
if (tmp > .999999999999999)
{
/* Station points coincide, use an Omni! */
*distance = 0.0;
*azimuth = 0.0;
return RIG_OK;
}
if (tmp < -.999999)
{
/*
* points are antipodal, it's straight down.
* Station is equal distance in all Azimuths.
* So take 180 Degrees of arc times 60 nm,
* and you get 10800 nm, or whatever units...
*/
*distance = 180.0 * ARC_IN_KM;
*azimuth = 0.0;
return RIG_OK;
}
arc = acos(tmp);
/*
* One degree of arc is 60 Nautical miles
* at the surface of the earth, 111.2 km, or 69.1 sm
* This method is easier than the one in the handbook
*/
*distance = ARC_IN_KM * RADIAN * arc;
/* Short Path */
/* Change to azimuth computation by Dave Freese, W1HKJ */
az = RADIAN * atan2(sin(lon2 - lon1) * cos(lat2),
(cos(lat1) * sin(lat2) - sin(lat1) * cos(lat2) * cos(lon2 - lon1)));
az = fmod(360.0 + az, 360.0);
if (az < 0.0)
{
az += 360.0;
}
else if (az >= 360.0)
{
az -= 360.0;
}
*azimuth = floor(az + 0.5);
return RIG_OK;
}
/**
* \brief Calculate the long path distance between two points.
* \param distance The shortpath distance
*
* Calculate the long path (respective of the short path)
* of a given distance.
*
* \return the distance in kilometers for the opposite path.
*
* \sa qrb()
*/
double HAMLIB_API distance_long_path(double distance)
{
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
return (ARC_IN_KM * 360.0) - distance;
}
/**
* \brief Calculate the long path bearing between two points.
* \param azimuth The shortpath bearing--0.0 to 360.0 degrees
*
* Calculate the long path (respective of the short path)
* of a given bearing.
*
* \return the azimuth in decimal degrees for the opposite path or
* -RIG_EINVAL upon input error (outside the range of 0.0 to 360.0).
*
* \sa qrb()
*/
double HAMLIB_API azimuth_long_path(double azimuth)
{
rot_debug(RIG_DEBUG_VERBOSE, "%s called\n", __func__);
if (azimuth == 0.0 || azimuth == 360.0)
{
return 180.0;
}
else if (azimuth > 0.0 && azimuth < 180.0)
{
return 180.0 + azimuth;
}
else if (azimuth == 180.0)
{
return 0.0;
}
else if (azimuth > 180.0 && azimuth < 360.0)
{
return (180.0 - azimuth) * -1.0;
}
else
{
return -RIG_EINVAL;
}
}
/*! @} */
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