int slope_length(int r, int c, int dr, int dc)
{
CELL top_alt, bot_alt, ridge;
char asp_value;
double res, top_ls, bot_ls;
WAT_ALT wa;
if (sides == 8) {
if (r == dr)
res = window.ns_res;
else if (c == dc)
res = window.ew_res;
else
res = diag;
}
else { /* sides == 4 */
bseg_get(&asp, &asp_value, dr, dc);
if (r == dr) {
if (asp_value == 2 || asp_value == 6)
res = window.ns_res;
else /* asp_value == 4, 8, -2, -4, -6, or -8 */
res = diag; /* how can res be diag with sides == 4??? */
}
else { /* c == dc */
if (asp_value == 4 || asp_value == 8)
res = window.ew_res;
else /* asp_value == 2, 6, -2, -4, -6, or -8 */
res = diag;
}
}
dseg_get(&s_l, &top_ls, r, c);
if (top_ls == half_res)
top_ls = res;
else
top_ls += res;
dseg_put(&s_l, &top_ls, r, c);
seg_get(&watalt, (char *) &wa, r, c);
top_alt = wa.ele;
seg_get(&watalt, (char *) &wa, dr, dc);
bot_alt = wa.ele;
if (top_alt > bot_alt) {
dseg_get(&s_l, &bot_ls, dr, dc);
if (top_ls > bot_ls) {
bot_ls = top_ls + res;
dseg_put(&s_l, &bot_ls, dr, dc);
cseg_get(&r_h, &ridge, r, c);
cseg_put(&r_h, &ridge, dr, dc);
}
}
return 0;
}
int sg_factor(void)
{
int r, c;
CELL low_elev, hih_elev;
double height, length, S, sin_theta;
WAT_ALT wa;
ASP_FLAG af;
G_message(_("SECTION 5: RUSLE LS and/or S factor determination."));
for (r = nrows - 1; r >= 0; r--) {
G_percent(nrows - r, nrows, 3);
for (c = ncols - 1; c >= 0; c--) {
seg_get(&aspflag, (char *)&af, r, c);
if (FLAG_GET(af.flag, NULLFLAG))
continue;
seg_get(&watalt, (char *) &wa, r, c);
low_elev = wa.ele;
cseg_get(&r_h, &hih_elev, r, c);
dseg_get(&s_l, &length, r, c);
height = 1.0 * (hih_elev - low_elev) / ele_scale;
if (length > max_length) {
height *= max_length / length;
length = max_length;
}
sin_theta = height / sqrt(height * height + length * length);
if (height / length < .09)
S = 10.8 * sin_theta + .03;
else
S = 16.8 * sin_theta - .50;
if (ls_flag) {
length *= METER_TO_FOOT;
len_slp_equ(length, sin_theta, S, r, c);
}
if (sg_flag) {
dseg_put(&s_g, &S, r, c);
}
}
}
G_percent(nrows, nrows, 1); /* finish it */
return 0;
}
int len_slp_equ(double slope_length, double sin_theta, double S, int r, int c)
{
double rill, s_l_exp, /* m */
rill_ratio, /* Beta */
LS;
rill_ratio = (sin_theta / 0.0896) / (3.0 * pow(sin_theta, 0.8) + 0.56);
if (ril_flag) {
dseg_get(&ril, &rill, r, c);
}
else if (ril_value >= 0.0) {
rill = ril_value;
}
else
rill = 0.0;
/* rill_ratio equation from Steve Warren */
rill_ratio *= .5 + .005 * rill + .0001 * rill * rill;
s_l_exp = rill_ratio / (1 + rill_ratio);
LS = S * pow((slope_length / 72.6), s_l_exp);
dseg_put(&l_s, &LS, r, c);
return 0;
}
int find_con(int r, int c, double *d1, double *d2, DCELL * con1, DCELL * con2)
{
int ct, low_ct, node_ct;
int rr, cc, dor, doc;
double dd, shortest;
DCELL value;
G_set_d_null_value(con1, 1);
G_set_d_null_value(con2, 1);
*d1 = *d2 = 1.0;
shortest = nrows * ncols;
for (rr = minr; rr <= maxr; rr++) {
for (cc = minc; cc <= maxc; cc++)
FLAG_UNSET(seen, rr, cc);
}
minr = nrows;
minc = ncols;
maxr = maxc = -1;
FLAG_SET(seen, r, c);
if (r < minr)
minr = r;
if (r > maxr)
maxr = r;
if (c < minc)
minc = c;
if (c > maxc)
maxc = c;
node_ct = 0;
zero = addpts(zero, r, c, r, c, &node_ct);
low_ct = 0;
while (1) {
ct = low_ct++;
if (node_ct <= ct)
return 1;
rr = zero[ct].r;
cc = zero[ct].c;
dor = ABS(rr - r);
doc = ABS(cc - c);
if (rr >= 0 && cc >= 0 && rr < nrows && cc < ncols
&& zero[ct].d < shortest && !flag_get(mask, rr, cc)) {
dseg_get(&con, rr, cc, &value);
if (G_is_d_null_value(&value))
zero = addpts(zero, r, c, rr, cc, &node_ct);
else if (G_is_d_null_value(con1)) {
*con1 = value;
*d1 = MIN(dor, doc) * 1.414 + ABS(dor - doc);
shortest = *d1 * 2.0 * i_val_l_f;
}
else if (*con1 == value) {
dd = MIN(dor, doc) * 1.414 + ABS(dor - doc);
if (dd < *d1) {
*d1 = dd;
shortest = dd * 2.0 * i_val_l_f;
}
}
else if (G_is_d_null_value(con2)) {
*con2 = value;
*d2 = MIN(dor, doc) * 1.414 + ABS(dor - doc);
shortest = *d2;
}
else {
dd = MIN(dor, doc) * 1.414 + ABS(dor - doc);
shortest = MIN(shortest, dd);
}
}
}
return 0;
}
