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/* Algorithm to locate a destination by distance measurement:
*/
#include <stdio.h>
#include <errno.h>
#include <math.h>
#include "geo.h"
#include "locate.h"
#define CIRCLE_PROBE 30.0
#define FINETUNE_RADIUS 5.0
extern double debug_long, debug_lat, debug_x_scale;
extern FILE *debug_fp;
extern int log_debug;
static double finetune_x[6], finetune_y[6], finetune_dist[6];
int locate_cell(struct probe *probe_first, double *min_x, double *min_y)
{
struct probe *probe, *min_probe;
int i, test_steps, optimized;
double min_dist, dist, x, y, rad, temp;
double circle_probe, finetune_radius;
/* convert meters into degrees */
circle_probe = CIRCLE_PROBE / (EQUATOR_RADIUS * PI / 180.0);
finetune_radius = FINETUNE_RADIUS / (EQUATOR_RADIUS * PI / 180.0);
if (log_debug) {
fprintf(debug_fp, "<Folder>\n");
fprintf(debug_fp, "\t<name>Debug Locator</name>\n");
fprintf(debug_fp, "\t<open>0</open>\n");
fprintf(debug_fp, "\t<visibility>0</visibility>\n");
}
/* get probe of minimum distance */
min_probe = NULL;
probe = probe_first;
min_dist = 42;
i = 0;
while (probe) {
if (log_debug) {
fprintf(debug_fp, "\t<Placemark>\n");
fprintf(debug_fp, "\t\t<name>MEAS</name>\n");
fprintf(debug_fp, "\t\t<visibility>0</visibility>\n");
fprintf(debug_fp, "\t\t<LineString>\n");
fprintf(debug_fp, "\t\t\t<tessellate>1</tessellate>\n");
fprintf(debug_fp, "\t\t\t<coordinates>\n");
rad = 2.0 * 3.1415927 / 35;
for (i = 0; i < 35; i++) {
x = probe->x + probe->dist * sin(rad * i);
y = probe->y + probe->dist * cos(rad * i);
fprintf(debug_fp, "%.8f,%.8f\n", debug_long +
x * debug_x_scale, debug_lat + y);
}
fprintf(debug_fp, "\t\t\t</coordinates>\n");
fprintf(debug_fp, "\t\t</LineString>\n");
fprintf(debug_fp, "\t</Placemark>\n");
}
if (!min_probe || probe->dist < min_dist) {
min_probe = probe;
min_dist = probe->dist;
}
probe = probe->next;
i++;
}
if (i < 3) {
fprintf(stderr, "Need at least 3 points\n");
return -EINVAL;
}
/* calculate the number of steps to search for destination point */
test_steps = 2.0 * 3.1415927 * min_probe->dist / circle_probe;
rad = 2.0 * 3.1415927 / test_steps;
if (log_debug) {
fprintf(debug_fp, "\t<Placemark>\n");
fprintf(debug_fp, "\t\t<name>Smallest MEAS</name>\n");
fprintf(debug_fp, "\t\t<visibility>0</visibility>\n");
fprintf(debug_fp, "\t\t<LineString>\n");
fprintf(debug_fp, "\t\t\t<tessellate>1</tessellate>\n");
fprintf(debug_fp, "\t\t\t<coordinates>\n");
}
/* search on a circle for the location of the lowest distance
* to the radius with the greatest distance */
min_dist = 42;
*min_x = *min_y = 42;
for (i = 0; i < test_steps; i++) {
x = min_probe->x + min_probe->dist * sin(rad * i);
y = min_probe->y + min_probe->dist * cos(rad * i);
if (log_debug)
fprintf(debug_fp, "%.8f,%.8f\n", debug_long +
x * debug_x_scale, debug_lat + y);
/* look for greatest distance */
dist = 0;
probe = probe_first;
while (probe) {
if (probe != min_probe) {
/* distance to the radius */
temp = distonplane(probe->x, probe->y, x, y);
temp -= probe->dist;
if (temp < 0)
temp = -temp;
if (temp > dist)
dist = temp;
}
probe = probe->next;
}
if (i == 0 || dist < min_dist) {
min_dist = dist;
*min_x = x;
*min_y = y;
}
}
if (log_debug) {
fprintf(debug_fp, "\t\t\t</coordinates>\n");
fprintf(debug_fp, "\t\t</LineString>\n");
fprintf(debug_fp, "\t</Placemark>\n");
fprintf(debug_fp, "\t<Placemark>\n");
fprintf(debug_fp, "\t\t<name>Finetune</name>\n");
fprintf(debug_fp, "\t\t<visibility>0</visibility>\n");
fprintf(debug_fp, "\t\t<LineString>\n");
fprintf(debug_fp, "\t\t\t<tessellate>1</tessellate>\n");
fprintf(debug_fp, "\t\t\t<coordinates>\n");
}
min_dist = 9999999999.0;
tune_again:
if (log_debug)
fprintf(debug_fp, "%.8f,%.8f\n", debug_long +
*min_x * debug_x_scale, debug_lat + *min_y);
/* finetune the point */
rad = 2.0 * 3.1415927 / 6;
for (i = 0; i < 6; i++) {
x = *min_x + finetune_radius * sin(rad * i);
y = *min_y + finetune_radius * cos(rad * i);
/* search for the point with the lowest sum of distances */
dist = 0;
probe = probe_first;
while (probe) {
/* distance to the radius */
temp = distonplane(probe->x, probe->y, x, y);
temp -= probe->dist;
if (temp < 0)
temp = -temp;
dist += temp;
probe = probe->next;
}
finetune_dist[i] = dist;
finetune_x[i] = x;
finetune_y[i] = y;
}
optimized = 0;
for (i = 0; i < 6; i++) {
if (finetune_dist[i] < min_dist) {
min_dist = finetune_dist[i];
*min_x = finetune_x[i];
*min_y = finetune_y[i];
optimized = 1;
}
}
if (optimized)
goto tune_again;
if (log_debug) {
fprintf(debug_fp, "\t\t\t</coordinates>\n");
fprintf(debug_fp, "\t\t</LineString>\n");
fprintf(debug_fp, "\t</Placemark>\n");
fprintf(debug_fp, "</Folder>\n");
}
return 0;
}
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