diff --git a/Makefile b/Makefile
index efffcaf5..cbd12f7a 100644
--- a/Makefile
+++ b/Makefile
@@ -72,7 +72,7 @@ tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpul
 tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
-unit: unit.o text.o drop.o
+unit: unit.o text.o drop.o projection.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 -include $(wildcard *.d)
diff --git a/unit.cpp b/unit.cpp
index bb7efdb5..02bb50c8 100644
--- a/unit.cpp
+++ b/unit.cpp
@@ -2,6 +2,8 @@
 #include "catch/catch.hpp"
 #include "text.hpp"
 #include "drop.hpp"
+#include "geometry.hpp"
+#include "projection.hpp"
 
 unsigned int additional[256] = {0};
 
@@ -37,3 +39,105 @@ TEST_CASE("prep drop states", "[prep_drop_state]") {
 	REQUIRE(ds[14].interval == 4);
 	REQUIRE(ds[0].interval == 65536);
 }
+
+TEST_CASE("select minzoom", "[calc_feature_minzoom]") {
+    const int maxzoom = 3;
+
+    struct drop_state ds[maxzoom + 1];
+    struct index ix;
+    long long wx, wy;
+    int minzoom;
+
+    prep_drop_states(ds, maxzoom, maxzoom, 2);
+    ix.t = VT_POINT;
+    
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-87.635236553223379, 41.84796128336411, 32, &wx, &wy); // Chicago
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Chicago %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.31532231603904, 47.600423319460475, 32, &wx, &wy); // Seattle
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Seattle %d\n", ix.ix, minzoom);
+
+    lonlat2tile(-122.6819359, 45.5219697, 32, &wx, &wy); // Portland
+    ix.ix = encode_hilbert(wx, wy);
+    minzoom = calc_feature_minzoom(&ix, ds, maxzoom, 1);
+    printf("%llu Portland %d\n", ix.ix, minzoom);
+}