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direwolf/latlong.c

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//
// This file is part of Dire Wolf, an amateur radio packet TNC.
//
// Copyright (C) 2013, 2014, 2015 John Langner, WB2OSZ
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 2 of the License, or
// (at your option) any later version.
//
// This program 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with this program. If not, see <http://www.gnu.org/licenses/>.
//
/*------------------------------------------------------------------
*
* Module: latlong.c
*
* Purpose: Various functions for dealing with latitude and longitude.
*
* Description: Originally, these were scattered around in many places.
* Over time they might all be gathered into one place
* for consistency, reuse, and easier maintenance.
*
*---------------------------------------------------------------*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
#include <ctype.h>
#include <time.h>
#include <math.h>
#include <assert.h>
#include "direwolf.h"
#include "latlong.h"
#include "textcolor.h"
/*------------------------------------------------------------------
*
* Name: latitude_to_str
*
* Purpose: Convert numeric latitude to string for transmission.
*
* Inputs: dlat - Floating point degrees.
* ambiguity - If 1, 2, 3, or 4, blank out that many trailing digits.
*
* Outputs: slat - String in format ddmm.mm[NS]
*
* Returns: None
*
*----------------------------------------------------------------*/
void latitude_to_str (double dlat, int ambiguity, char *slat)
{
char hemi; /* Hemisphere: N or S */
int ideg; /* whole number of degrees. */
double dmin; /* Minutes after removing degrees. */
char smin[8]; /* Minutes in format mm.mm */
if (dlat < -90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is less than -90. Changing to -90.n");
dlat = -90.;
}
if (dlat > 90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is greater than 90. Changing to 90.n");
dlat = 90.;
}
if (dlat < 0) {
dlat = (- dlat);
hemi = 'S';
}
else {
hemi = 'N';
}
ideg = (int)dlat;
dmin = (dlat - ideg) * 60.;
sprintf (smin, "%05.2f", dmin);
/* Due to roundoff, 59.9999 could come out as "60.00" */
if (smin[0] == '6') {
smin[0] = '0';
ideg++;
}
sprintf (slat, "%02d%s%c", ideg, smin, hemi);
if (ambiguity >= 1) {
slat[6] = ' ';
if (ambiguity >= 2) {
slat[5] = ' ';
if (ambiguity >= 3) {
slat[3] = ' ';
if (ambiguity >= 4) {
slat[2] = ' ';
}
}
}
}
} /* end latitude_to_str */
/*------------------------------------------------------------------
*
* Name: longitude_to_str
*
* Purpose: Convert numeric longitude to string for transmission.
*
* Inputs: dlong - Floating point degrees.
* ambiguity - If 1, 2, 3, or 4, blank out that many trailing digits.
*
* Outputs: slat - String in format dddmm.mm[NS]
*
* Returns: None
*
*----------------------------------------------------------------*/
void longitude_to_str (double dlong, int ambiguity, char *slong)
{
char hemi; /* Hemisphere: N or S */
int ideg; /* whole number of degrees. */
double dmin; /* Minutes after removing degrees. */
char smin[8]; /* Minutes in format mm.mm */
if (dlong < -180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Longitude is less than -180. Changing to -180.n");
dlong = -180.;
}
if (dlong > 180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Longitude is greater than 180. Changing to 180.n");
dlong = 180.;
}
if (dlong < 0) {
dlong = (- dlong);
hemi = 'W';
}
else {
hemi = 'E';
}
ideg = (int)dlong;
dmin = (dlong - ideg) * 60.;
sprintf (smin, "%05.2f", dmin);
/* Due to roundoff, 59.9999 could come out as "60.00" */
if (smin[0] == '6') {
smin[0] = '0';
ideg++;
}
sprintf (slong, "%03d%s%c", ideg, smin, hemi);
/*
* The spec says position ambiguity in latitude also
* applies to longitude automatically.
* Blanking longitude digits is not necessary but I do it
* because it makes things clearer.
*/
if (ambiguity >= 1) {
slong[7] = ' ';
if (ambiguity >= 2) {
slong[6] = ' ';
if (ambiguity >= 3) {
slong[4] = ' ';
if (ambiguity >= 4) {
slong[3] = ' ';
}
}
}
}
} /* end longitude_to_str */
/*------------------------------------------------------------------
*
* Name: latitude_to_comp_str
*
* Purpose: Convert numeric latitude to compressed string for transmission.
*
* Inputs: dlat - Floating point degrees.
*
* Outputs: slat - String in format yyyy.
*
*----------------------------------------------------------------*/
void latitude_to_comp_str (double dlat, char *clat)
{
int y, y0, y1, y2, y3;
if (dlat < -90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is less than -90. Changing to -90.n");
dlat = -90.;
}
if (dlat > 90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is greater than 90. Changing to 90.n");
dlat = 90.;
}
y = (int)round(380926. * (90. - dlat));
y0 = y / (91*91*91);
y -= y0 * (91*91*91);
y1 = y / (91*91);
y -= y1 * (91*91);
y2 = y / (91);
y -= y2 * (91);
y3 = y;
clat[0] = y0 + 33;
clat[1] = y1 + 33;
clat[2] = y2 + 33;
clat[3] = y3 + 33;
}
/*------------------------------------------------------------------
*
* Name: longitude_to_comp_str
*
* Purpose: Convert numeric longitude to compressed string for transmission.
*
* Inputs: dlong - Floating point degrees.
*
* Outputs: slat - String in format xxxx.
*
*----------------------------------------------------------------*/
void longitude_to_comp_str (double dlong, char *clon)
{
int x, x0, x1, x2, x3;
if (dlong < -180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Longitude is less than -180. Changing to -180.n");
dlong = -180.;
}
if (dlong > 180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Longitude is greater than 180. Changing to 180.n");
dlong = 180.;
}
x = (int)round(190463. * (180. + dlong));
x0 = x / (91*91*91);
x -= x0 * (91*91*91);
x1 = x / (91*91);
x -= x1 * (91*91);
x2 = x / (91);
x -= x2 * (91);
x3 = x;
clon[0] = x0 + 33;
clon[1] = x1 + 33;
clon[2] = x2 + 33;
clon[3] = x3 + 33;
}
/*------------------------------------------------------------------
*
* Name: latitude_to_nmea
*
* Purpose: Convert numeric latitude to strings for NMEA sentence.
*
* Inputs: dlat - Floating point degrees.
*
* Outputs: slat - String in format ddmm.mmmm
* hemi - Hemisphere or empty string.
*
* Returns: None
*
*----------------------------------------------------------------*/
void latitude_to_nmea (double dlat, char *slat, char *hemi)
{
int ideg; /* whole number of degrees. */
double dmin; /* Minutes after removing degrees. */
char smin[10]; /* Minutes in format mm.mmmm */
if (dlat == G_UNKNOWN) {
strcpy (slat, "");
strcpy (hemi, "");
return;
}
if (dlat < -90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is less than -90. Changing to -90.n");
dlat = -90.;
}
if (dlat > 90.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("Latitude is greater than 90. Changing to 90.n");
dlat = 90.;
}
if (dlat < 0) {
dlat = (- dlat);
strcpy (hemi, "S");
}
else {
strcpy (hemi, "N");
}
ideg = (int)dlat;
dmin = (dlat - ideg) * 60.;
sprintf (smin, "%07.4f", dmin);
/* Due to roundoff, 59.99999 could come out as "60.0000" */
if (smin[0] == '6') {
smin[0] = '0';
ideg++;
}
sprintf (slat, "%02d%s", ideg, smin);
} /* end latitude_to_str */
/*------------------------------------------------------------------
*
* Name: longitude_to_nmea
*
* Purpose: Convert numeric longitude to strings for NMEA sentence.
*
* Inputs: dlong - Floating point degrees.
*
* Outputs: slong - String in format dddmm.mmmm
* hemi - Hemisphere or empty string.
*
* Returns: None
*
*----------------------------------------------------------------*/
void longitude_to_nmea (double dlong, char *slong, char *hemi)
{
int ideg; /* whole number of degrees. */
double dmin; /* Minutes after removing degrees. */
char smin[10]; /* Minutes in format mm.mmmm */
if (dlong == G_UNKNOWN) {
strcpy (slong, "");
strcpy (hemi, "");
return;
}
if (dlong < -180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("longitude is less than -180. Changing to -180.n");
dlong = -180.;
}
if (dlong > 180.) {
text_color_set(DW_COLOR_ERROR);
dw_printf ("longitude is greater than 180. Changing to 180.n");
dlong = 180.;
}
if (dlong < 0) {
dlong = (- dlong);
strcpy (hemi, "W");
}
else {
strcpy (hemi, "E");
}
ideg = (int)dlong;
dmin = (dlong - ideg) * 60.;
sprintf (smin, "%07.4f", dmin);
/* Due to roundoff, 59.99999 could come out as "60.0000" */
if (smin[0] == '6') {
smin[0] = '0';
ideg++;
}
sprintf (slong, "%03d%s", ideg, smin);
} /* end longitude_to_nmea */
/*------------------------------------------------------------------
*
* Function: latitude_from_nmea
*
* Purpose: Convert NMEA latitude encoding to degrees.
*
* Inputs: pstr - Pointer to numeric string.
* phemi - Pointer to following field. Should be N or S.
*
* Returns: Double precision value in degrees. Negative for South.
*
* Description: Latitude field has
* 2 digits for degrees
* 2 digits for minutes
* period
* Variable number of fractional digits for minutes.
* I've seen 2, 3, and 4 fractional digits.
*
*
* Bugs: Very little validation of data.
*
* Errors: Return constant G_UNKNOWN for any type of error.
* Could we use special "NaN" code?
*
*------------------------------------------------------------------*/
double latitude_from_nmea (char *pstr, char *phemi)
{
double lat;
if ( ! isdigit((unsigned char)(pstr[0]))) return (G_UNKNOWN);
if (pstr[4] != '.') return (G_UNKNOWN);
lat = (pstr[0] - '0') * 10 + (pstr[1] - '0') + atof(pstr+2) / 60.0;
if (lat < 0 || lat > 90) {
text_color_set(DW_COLOR_ERROR);
dw_printf("Error: Latitude not in range of 0 to 90.\n");
}
// Saw this one time:
// $GPRMC,000000,V,0000.0000,0,00000.0000,0,000,000,000000,,*01
// If location is unknown, I think the hemisphere should be
// an empty string. TODO: Check on this.
// 'V' means void, so sentence should be discarded rather than
// trying to extract any data from it.
if (*phemi != 'N' && *phemi != 'S' && *phemi != '\0') {
text_color_set(DW_COLOR_ERROR);
dw_printf("Error: Latitude hemisphere should be N or S.\n");
}
if (*phemi == 'S') lat = ( - lat);
return (lat);
}
/*------------------------------------------------------------------
*
* Function: longitude_from_nmea
*
* Purpose: Convert NMEA longitude encoding to degrees.
*
* Inputs: pstr - Pointer to numeric string.
* phemi - Pointer to following field. Should be E or W.
*
* Returns: Double precision value in degrees. Negative for West.
*
* Description: Longitude field has
* 3 digits for degrees
* 2 digits for minutes
* period
* Variable number of fractional digits for minutes
*
*
* Bugs: Very little validation of data.
*
* Errors: Return constant G_UNKNOWN for any type of error.
* Could we use special "NaN" code?
*
*------------------------------------------------------------------*/
double longitude_from_nmea (char *pstr, char *phemi)
{
double lon;
if ( ! isdigit((unsigned char)(pstr[0]))) return (G_UNKNOWN);
if (pstr[5] != '.') return (G_UNKNOWN);
lon = (pstr[0] - '0') * 100 + (pstr[1] - '0') * 10 + (pstr[2] - '0') + atof(pstr+3) / 60.0;
if (lon < 0 || lon > 180) {
text_color_set(DW_COLOR_ERROR);
dw_printf("Error: Longitude not in range of 0 to 180.\n");
}
if (*phemi != 'E' && *phemi != 'W' && *phemi != '\0') {
text_color_set(DW_COLOR_ERROR);
dw_printf("Error: Longitude hemisphere should be E or W.\n");
}
if (*phemi == 'W') lon = ( - lon);
return (lon);
}
/*------------------------------------------------------------------
*
* Function: ll_distance_km
*
* Purpose: Calculate distance between two locations.
*
* Inputs: lat1, lon1 - One location, in degrees.
* lat2, lon2 - other location
*
* Returns: Distance in km.
*
* Description: The Ubiquitous Haversine formula.
*
*------------------------------------------------------------------*/
#define R 6371
double ll_distance_km (double lat1, double lon1, double lat2, double lon2)
{
double a;
lat1 *= M_PI / 180;
lon1 *= M_PI / 180;
lat2 *= M_PI / 180;
lon2 *= M_PI / 180;
a = pow(sin((lat2-lat1)/2),2) + cos(lat1) * cos(lat2) * pow(sin((lon2-lon1)/2),2);
return (R * 2 *atan2(sqrt(a), sqrt(1-a)));
}
/*------------------------------------------------------------------
*
* Function: ll_from_grid_square
*
* Purpose: Convert Maidenhead locator to latitude and longitude.
*
* Inputs: maidenhead - 4 or 6 character grid square.
*
* Outputs: dlat, dlon - Latitude and longitude.
* Original values unchanged if error.
*
* Returns: 1 for success, 0 if error.
*
* Bug: This does not check for invalid values.
*
* Reference: A good converter for spot checking:
* http://home.arcor.de/waldemar.kebsch/The_Makrothen_Contest/fmaidenhead.html
*
* Rambling: What sort of resolution does this provide?
* For 8 character form, each latitude unit is 0.25 minute.
* (Longitude can be up to twice that around the equator.)
* 6371 km * 2 * pi * 0.25 / 60 / 360 = 0.463 km. Is that right?
*
* Using this calculator, http://www.earthpoint.us/Convert.aspx
*
* FN42MA00 --> 19T 334361mE 4651711mN
* FN42MA11 --> 19T 335062mE 4652157mN
* ------ -------
* 701 446 meters difference.
*
*------------------------------------------------------------------*/
int ll_from_grid_square (char *maidenhead, double *dlat, double *dlon)
{
double lat, lon;
char mh[16];
if (strlen(maidenhead) != 4 && strlen(maidenhead) != 6) {
text_color_set(DW_COLOR_ERROR);
dw_printf("Maidenhead locator \"%s\" must 4 or 6 characters in this context.\n", maidenhead);
return (0);
}
strcpy (mh, maidenhead);
if (islower(mh[0])) mh[0] = toupper(mh[0]);
if (islower(mh[1])) mh[1] = toupper(mh[1]);
if (mh[0] < 'A' || mh[0] > 'R' || mh[1] < 'A' || mh[1] > 'R') {
text_color_set(DW_COLOR_ERROR);
dw_printf("The first pair of characters in Maidenhead locator \"%s\" must be in range of A thru R.\n", maidenhead);
return (0);
}
if ( ! isdigit(mh[2]) || ! isdigit(mh[3]) ) {
text_color_set(DW_COLOR_ERROR);
dw_printf("The second pair of characters in Maidenhead locator \"%s\" must be digits.\n", maidenhead);
return (0);
}
/* Lon: 360 deg / 18 squares = 20 deg / square */
/* Lat: 180 deg / 18 squares = 10 deg / square */
lon = (mh[0] - 'A') * 20 - 180;
lat = (mh[1] - 'A') * 10 - 90;
/* Lon: 20 deg / 10 squares = 2 deg / square */
/* Lat: 10 deg / 10 squares = 1 deg / square */
lon += (mh[2] - '0') * 2;
lat += (mh[3] - '0');
if (strlen(mh) >=6) {
if (islower(mh[4])) mh[4] = toupper(mh[4]);
if (islower(mh[5])) mh[5] = toupper(mh[5]);
if (mh[4] < 'A' || mh[4] > 'X' || mh[5] < 'A' || mh[5] > 'X') {
text_color_set(DW_COLOR_ERROR);
dw_printf("The third pair of characters in Maidenhead locator \"%s\" must be in range of A thru X.\n", maidenhead);
return (0);
}
/* Lon: 2 deg / 24 squares = 5 minutes / square */
/* Lat: 1 deg / 24 squares = 2.5 minutes / square */
lon += (mh[4] - 'A') * 5.0 / 60.0;
lat += (mh[5] - 'A') * 2.5 / 60.0;
if (strlen(mh) >= 8) {
if ( ! isdigit(mh[6]) || ! isdigit(mh[7]) ) {
text_color_set(DW_COLOR_ERROR);
dw_printf("The fourth pair of characters in Maidenhead locator \"%s\" must be digits.\n", maidenhead);
return (0);
}
/* Lon: 5 min / 10 squares = 0.5 minutes / square */
/* Lat: 2.5 min / 10 squares = 0.25 minutes / square */
lon += (mh[6] - '0') * 0.50 / 60.0;
lat += (mh[7] - '0') * 0.25 / 60.0;
lon += 0.250 / 60.0; /* Move from corner to center of square */
lat += 0.125 / 60.0;
}
else {
lon += 2.5 / 60.0; /* Move from corner to center of square */
lat += 1.25 / 60.0;
}
}
else {
lon += 1.0; /* Move from corner to center of square */
lat += 0.5;
}
//text_color_set(DW_COLOR_DEBUG);
//dw_printf("DEBUG: Maidenhead conversion \"%s\" -> %.6f %.6f\n", maidenhead, lat, lon);
*dlat = lat;
*dlon = lon;
return (1);
}
/* end ll_from_grid_square */
/* end latlong.c */
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