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| -rw-r--r-- | README.md | 9 | ||||
| -rwxr-xr-x | adif2mpw | 8 | ||||
| -rw-r--r-- | gridcal.c | 146 |
3 files changed, 163 insertions, 0 deletions
diff --git a/README.md b/README.md new file mode 100644 index 0000000..6aa4d19 --- /dev/null +++ b/README.md @@ -0,0 +1,9 @@ +gridcal -- compute the great-circle distance between two grid locators +====================================================================== + +`gridcal` computed the short-path great-circle distance between two grid +locators. The Grid Locator System divides Earth into a series of +rectangles identified by a combination of letters and numbers, so that +the approximate position of a point can be expressed with a short +identifier like IO91vl. + diff --git a/adif2mpw b/adif2mpw new file mode 100755 index 0000000..189127a --- /dev/null +++ b/adif2mpw @@ -0,0 +1,8 @@ +#!/bin/sh + +FIN="$1" + +for i in \ + $(sed -En 's/.*(<GRIDSQUARE[^<]*) (<MY_GRIDSQUARE[^<]*) .* (<TX_PWR[^<]*).*/\1|\2|\3/g;s/<[^>]*>//g;/.* .* .*/d;p' $FIN) + do ./gridcal $(echo "$i" | sed -E 's/\|/ /g'); done 2>/dev/null + diff --git a/gridcal.c b/gridcal.c new file mode 100644 index 0000000..97e8cf9 --- /dev/null +++ b/gridcal.c @@ -0,0 +1,146 @@ +/** +* +* Get two grid locators and compute the great-circle distance +* between the centers of the two corresponding squares +* +* +* Usage: gridcal <grid1> [<grid2> [<pwr>]] +* +*/ + +#include <stdio.h> +#include <stdlib.h> +#include <math.h> +#include <string.h> +#include <ctype.h> + +#define MIN(a,b) ((a)>(b)?(b):(a)) + +double R = 6371; + +typedef struct { + double lat; + double lon; +} latlon_t; + + +void usage(char *argv0){ + + printf("Usage: %s <grid1> <grid2> [<pwr>]", argv0); + exit(1); +} + +int check_input(char *s){ + int S = strlen(s); +#ifdef __DEBUG__ + fprintf(stderr, "locator: %s (length: %d)\n", s, S); +#endif + if (S>6 || S<4 || S%2 == 1 + || tolower(s[0]) < 'a' || tolower(s[0]) > 'r' + || tolower(s[1]) < 'a' || tolower(s[1]) > 'r' + || s[2] < '0' || s[2] > '9' + || s[3] < '0' || s[3] > '9' + || (S > 4 && (tolower(s[4]) < 'a' || tolower(s[4]) > 'x' + || tolower(s[5]) < 'a' || tolower(s[5]) > 'x'))) { + printf("Invalid locator: %s\n", s); + exit(1); + } +} + + +/** +* +* This function takes a valid locator and returns the coordinates +* of the centre of the corresponding square in the latlon_t structure +* +*/ + +void grid_to_latlon(char *s, latlon_t *c){ + + c->lat = c->lon = 0; + /* longitude first */ + c->lon += (tolower(s[0])-'a')*20.0 - 180; + c->lon += (s[2]-'0')*2.0; + /* we always consider the centre of the square, not the corner...*/ + if (strlen(s)>4){ + c->lon += (tolower(s[4]) - 'a') * 1.0/12 + 1.0/24; + } + else { + c->lon += 1.0; + } + + /* then latitude */ + c->lat += (tolower(s[1])-'a')*10.0 - 90; + c->lat += (s[3]-'0')*1.0; + /* we always consider the centre of the square, not the corner...*/ + if (strlen(s)>4){ + c->lat += (tolower(s[5]) - 'a') * 1.0/24 + 1.0/48; + } + else { + c->lat += 0.5; + } + c->lon = c->lon/180 * M_PI; + c->lat = c->lat/90 * M_PI_2; +} + +double heversine_dist(latlon_t *c1, latlon_t *c2){ + + double d=0.0, d1=0, d2=0; + + d1 = sin(0.5*(c2->lat - c1->lat)); + d1 = d1 * d1; + + d2 = sin(0.5*(c2->lon - c1->lon)); + d2 = d2 * d2; + d2 = d2 * cos(c1->lat) * cos(c2->lat); + + d = 2 * R * asin(sqrt(d1 + d2)); + return d; +} + + +int main(int argc, char *argv[]){ + + char loc1[7], loc2[7]; + int n1, n2; + latlon_t c1, c2; + double d; + double pwr; + + if (argc < 2){ + usage(argv[0]); + } + if (argc == 2){ + /* We only convert a grid locator to lat-long */ + n1=MIN(strlen(argv[1]),6); + strncpy(loc1, argv[1], n1); + loc1[n1] = '\0'; + check_input(loc1); + grid_to_latlon(loc1, &c1); + printf("%s %g %g\n", loc1, c1.lat, c1.lon); + exit(0); + } + + n1=MIN(strlen(argv[1]),6); + n2=MIN(strlen(argv[2]),6); + strncpy(loc1, argv[1], n1); + strncpy(loc2, argv[2], n2); + loc1[n1] = '\0'; + loc2[n2] = '\0'; + check_input(loc1); + check_input(loc2); + + grid_to_latlon(loc1, &c1); + grid_to_latlon(loc2, &c2); + + d = heversine_dist(&c1, &c2); + if (argc > 3){ + pwr = atof(argv[3]); + printf("%s %s %g %g %g %g %g\n", \ + loc1, loc2, d, d/1.60934, pwr, d/pwr, d/(1.60934*pwr)); + } + else { + printf("%s %s %g %g\n", loc1, loc2, d, d/1.60934); + } +} + |