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Reduce maxzooms being guessed a little: (#2)

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* Reduce maxzooms being guessed a little:

* Use 1.5 standard deviations, not 2, as the minimum distinguishable
* Give overlapping polygons and linestrings more distinct indices

* Add another drop rate guessing options, from the same metrics -zg uses

* Guard against using -rp without -zg
This commit is contained in:
Erica Fischer
2022-09-08 15:47:32 -07:00
committed by GitHub
parent a447dfc089
commit 073700aa38
66 changed files with 26708 additions and 25829 deletions
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main.cpp
+26 -1
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@@ -2074,7 +2074,7 @@ int read_input(std::vector<source> &sources, char *fname, int maxzoom, int minzo
// are typically lognormally distributed. Two standard deviations
// below the mean should be enough to distinguish most features.
double avg = exp(mean);
double nearby = exp(mean - 2 * stddev);
double nearby = exp(mean - 1.5 * stddev);
// Convert approximately from tile units to feet.
// See empirical data above for source
@@ -2117,6 +2117,24 @@ int read_input(std::vector<source> &sources, char *fname, int maxzoom, int minzo
if (changed) {
printf("Choosing a maxzoom of -z%d to keep most features distinct with cluster distance %d\n", maxzoom, cluster_distance);
}
if (droprate == -3) {
// This mysterious formula is the result of eyeballing the appropriate drop rate
// for several point tilesets using -zg and then fitting a curve to the pattern
// that emerged. It appears that if the standard deviation of the distances between
// features is small, the drop rate should be large because the features are evenly
// spaced, and if the standard deviation is large, the drop rate can be small because
// the features are in clumps.
droprate = exp(-0.7681 * log(stddev) + 1.582);
if (droprate < 0) {
droprate = 0;
}
if (!quiet) {
fprintf(stderr, "Choosing a drop rate of %f\n", droprate);
}
}
}
if (dist_count != 0) {
@@ -3044,6 +3062,8 @@ int main(int argc, char **argv) {
case 'r':
if (strcmp(optarg, "g") == 0) {
droprate = -2;
} else if (strcmp(optarg, "p") == 0) {
droprate = -3;
} else if (optarg[0] == 'g' || optarg[0] == 'f') {
droprate = -2;
if (optarg[0] == 'g') {
@@ -3254,6 +3274,11 @@ int main(int argc, char **argv) {
full_detail = 12;
}
if (droprate == -3 && !guess_maxzoom) {
fprintf(stderr, "Can't use -rp without either -zg or --smallest-maximum-zoom-guess\n");
exit(EXIT_FAILURE);
}
if (maxzoom > MAX_ZOOM) {
maxzoom = MAX_ZOOM;
fprintf(stderr, "Highest supported zoom is -z%d\n", maxzoom);