diff options
| -rw-r--r-- | Makefile | 13 | ||||
| -rw-r--r-- | README.md | 12 | ||||
| -rw-r--r-- | getgrid.c | 61 |
3 files changed, 82 insertions, 4 deletions
@@ -1,10 +1,11 @@ # gridcal - compute great-circle distance between two grid locators .POSIX: -SRC = gridcal.c +SRC = gridcal.c getgrid.c OBJ = ${SRC:.c=.o} +PROG= gridcal getgrid -all: options gridcal +all: options gridcal getgrid options: @echo "-+- build options -+-" @@ -15,11 +16,15 @@ options: @echo "-+-+-+-+-+-+-+-+-+-+-" gridcal: ${OBJ} - $(CC) $(LDFLAGS) -o $@ $(OBJ) -lm + $(CC) $(LDFLAGS) -o $@ gridcal.o -lm + +getgrid: ${OBJ} + $(CC) $(LDFLAGS) -o $@ getgrid.o -lm + debug: clean ${MAKE} CFLAGS="${DEBUG}" all clean: - rm -f gridcal ${OBJ} + rm -f ${PROG} ${OBJ} @@ -36,6 +36,18 @@ The latter can be useful to check if a QSO with another ham radio station qualifies for one of the thousand miles per Watt awards. +`getgrid` -- compute the grid locator associated to lat-long coordinates +======================================================================== + +`getgrid` is a simple tool to compute the grid locator associated to a +latitude/longitude pair. The coordinates must be in degrees. + +Usage: getgrid <lat> <lon> + +Example: + + getgrid + Dependencies ============ diff --git a/getgrid.c b/getgrid.c new file mode 100644 index 0000000..84ac26d --- /dev/null +++ b/getgrid.c @@ -0,0 +1,61 @@ +/** +* +* Compute the grid locator associated to a pair of latitude/longitude +* coordinates, given in degrees +* +*/ + +#include <stdio.h> +#include <stdlib.h> +#include <math.h> + +void latlon_to_grid(double lat, double lon, char *loc){ + + double q; + + q = (int)((lon + 180)/20); + lon = (q==0? lon: fmod(lon+180, 20)); + loc[0] = 'A' + q; + q = (int)((lat + 90)/10); + lat = (q==0? lat: fmod(lat+90, 10)); + loc[1] = 'A' + q; + q = (int)(lon/2); + lon = (q==0? lon: fmod(lon, 2)); + loc[2] = '0' + q; + q = (int)(lat); + lat = (q==0? lat: lat - q); + loc[3] = '0' + q; + q = (int)(lon*12); + loc[4] = 'A' + q; + q = (int)(lat*24); + loc[5] = 'A' + q; + loc[6] = '\0'; +} + +void usage(char s[]){ + printf("Usage: get_grid <lat> <lon>\n"); + exit(1); +} + +int main (int argc, char *argv[]){ + + double lat, lon; + char loc[7]; + + if (argc < 3){ + usage(argv[0]); + } + + lat = atof(argv[1]); + lon = atof(argv[2]); + while (lat < -90) lat +=180; + while (lat > 90) lat -=180; + while (lon < -180) lon += 360; + while (lon > 180) lon -= 360; + //fprintf(stderr, "lat: %g lon: %g\n", lat, lon); + latlon_to_grid(lat, lon, loc); + printf("%s\n", loc); + +} + + |