diff --git a/README.md b/README.md
index 14024f9d..8ef18d14 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@ Options
  * -n <i>name</i>: Human-readable name (default file.json)
  * -z <i>zoom</i>: Base zoom level (default 14)
  * -Z <i>zoom</i>: Lowest zoom level (default 0)
- * -d <i>detail</i>: Detail at base zoom level (default 12, for tile resolution of 4096)
+ * -d <i>detail</i>: Detail at base zoom level (default 26-basezoom, ~0.5m, for tile resolution of 4096 if -z14)
  * -D <i>detail</i>: Detail at lower zoom levels (default 10, for tile resolution of 1024) 
  * -x <i>name</i>: Exclude the named properties from all features
  * -X: Exclude all properties and encode only geometries
diff --git a/geojson.c b/geojson.c
index 40371e84..2320482e 100644
--- a/geojson.c
+++ b/geojson.c
@@ -20,7 +20,7 @@
 #include "projection.h"
 
 int low_detail = 10;
-int full_detail = 12;
+int full_detail = -1;
 
 #define GEOM_POINT 0                /* array of positions */
 #define GEOM_MULTIPOINT 1           /* array of arrays of positions */
@@ -581,6 +581,13 @@ int main(int argc, char **argv) {
 		}
 	}
 
+	if (full_detail <= 0) {
+		// ~0.5m accuracy at whatever zoom
+		// 12 bits (4096 units) at z14
+
+		full_detail = 26 - maxzoom;
+	}
+
 	if (outdir == NULL) {
 		fprintf(stderr, "%s: must specify -o out.mbtiles\n", argv[0]);
 		exit(EXIT_FAILURE);