diff --git a/src/Global/Contour/index.js b/src/Global/Contour/index.js
index cbe7f65..b4608d1 100644
--- a/src/Global/Contour/index.js
+++ b/src/Global/Contour/index.js
@@ -111,7 +111,7 @@ async function dialog(sdk) {
     if (e.target.checked) {
       show = true
       let height = sdk.viewer.camera.positionCartographic.height
-      if(height>16360) {
+      if (height > 16360) {
         let cartographic = sdk.viewer.camera.positionCartographic
         let options = {
           position: {
@@ -413,6 +413,9 @@ function showContour(sdk) {
       let gap = pos84.alt - mainContourHeight
       let gap2 = material.uniforms.spacing / (material.uniforms.secondaryLinesCount + 1)
       let activeHeight = Math.floor(gap / gap2) * gap2 + mainContourHeight
+      if (pos84.alt < 0) {
+        pos84.alt = 0
+      }
       if ((pos84.alt - activeHeight) > gap2 / 2) {
         activeHeight = activeHeight + gap2
       }
@@ -581,6 +584,10 @@ czm_material czm_getMaterial(czm_materialInput materialInput)
         outColor = vec4(0.0);
     }
 
+    if(materialInput.height<0.0) {
+      outColor = vec4(0.0);
+    }
+
     material.diffuse = outColor.rgb;
     material.alpha = outColor.a;
     return material;
diff --git a/src/Tools/index.js b/src/Tools/index.js
index a81f143..a06198c 100644
--- a/src/Tools/index.js
+++ b/src/Tools/index.js
@@ -123,8 +123,8 @@ class Tools {
     var cartographic = ellipsoid.cartesianToCartographic(cartesian3)
     var lat = Cesium.Math.toDegrees(cartographic.latitude)
     var lng = Cesium.Math.toDegrees(cartographic.longitude)
-    // var alt = cartographic.height < 0 ? 0 : cartographic.height
-    var alt = cartographic.height
+    var alt = cartographic.height < 0 ? 0 : cartographic.height
+    // var alt = cartographic.height
     return {
       lng: lng,
       lat: lat,