diff --git a/modules/mesh/height map b/modules/mesh/height map
index 9d4b7b7d4994850cf5c732a3efad119dc246b34d..061d0e547897166280927d40dbda782b26e6bc2f 100644
--- a/modules/mesh/height map	
+++ b/modules/mesh/height map	
@@ -374,7 +374,7 @@ function map_worker() {
       //
       for (var row = 0; row < h; ++row) {
          for (var col = 0; col < w; ++col) {
-            map[(h-1-row)*w+col] = -Number.MAX_VALUE
+            map[(h-1-row)*w+col] = zmin
             buf[(h-1-row)*w*4+col*4+0] = 0
             buf[(h-1-row)*w*4+col*4+1] = 0
             buf[(h-1-row)*w*4+col*4+2] = 0