diff --git a/SCANmap.cs b/SCANmap.cs
index e2883c9..78ee3eb 100644
--- a/SCANmap.cs
+++ b/SCANmap.cs
@@ -10,34 +10,50 @@ public class SCANmap
 			XKCDColors.Yellow,
 			XKCDColors.Red,
 			XKCDColors.Magenta,
-			XKCDColors.White,
 			XKCDColors.White
 		};
+		public static float startGradientHeight = -1500;// default range is from -1500 to 9000
+		public static float heightGradientRange = 10500;// default of 10500
+		private const float gradientSealevelPercent = 1500f/10500f;//indetifys the point to start using heightGradient for lerps
 
 		public static Color heightToColor(float val, int scheme) {
 			if(scheme == 1 || SCANcontroller.controller.colours == 1) {
-				return Color.Lerp(Color.black, Color.white, Mathf.Clamp((val + 1500f) / 9000f, 0, 1));
+				return Color.Lerp(Color.black, Color.white, Mathf.Clamp((val - startGradientHeight) / heightGradientRange, 0, 1));
 			}
 			Color c = Color.black;
-			if(val <= 0) {
-				val = (Mathf.Clamp(val, -1500, 0) + 1500) / 1000f;
-				c = Color.Lerp(XKCDColors.DarkPurple, XKCDColors.Cerulean, val);
-			} else {
-				val = (heightGradient.Length - 2) * Mathf.Clamp(val, 0, 7500) / 7500.0f;
-				c = Color.Lerp(heightGradient[(int)val], heightGradient[(int)val + 1], val - (int)val);
+			val -= startGradientHeight;
+			val /= heightGradientRange;
+			if (val<0f) {//below gradient range
+				c=XKCDColors.DarkPurple;
 			}
+			else if (val>=1f) {//above gradient range
+				c=heightGradient[heightGradient.Length-1];
+			}
+			else {//in gradient range
+				if (val<=gradientSealevelPercent) {
+					c = Color.Lerp(XKCDColors.DarkPurple, XKCDColors.Cerulean, val/gradientSealevelPercent );
+				} else {
+					val -= gradientSealevelPercent;//remove sealevel chunk
+					val /= (1f-gradientSealevelPercent);//realign the range from 0 to 1
+					val *= (heightGradient.Length-1);
+					c = Color.Lerp(heightGradient[(int)val], heightGradient[(int)val + 1], val - (int)val);
+				}
+			}	
 			return c;
 		}
 
 		public static Texture2D legend;
-		private static float legendMin, legendMax;
+		private static float legendMin, legendMax, legendstartGradientHeight, legendheightGradientRange;
 		private static int legendScheme;
 		public static Texture2D getLegend(float min, float max, int scheme) {
-			if(legend != null && legendMin == min && legendMax == max && legendScheme == scheme) return legend;
+			if( legend != null && legendMin == min && legendMax == max && legendScheme == scheme &&
+				legendstartGradientHeight == startGradientHeight && legendheightGradientRange == heightGradientRange ) return legend;
 			legend = new Texture2D(256, 1, TextureFormat.RGB24, false);
 			legendMin = min;
 			legendMax = max;
 			legendScheme = scheme;
+			legendstartGradientHeight = startGradientHeight;
+			legendheightGradientRange = heightGradientRange;
 			Color[] pix = legend.GetPixels();
 			for(int x=0; x<256; ++x) {
 				float val = (x * (max - min)) / 256f + min;
@@ -412,4 +428,4 @@ public void resetMap(int mode) {
 			resetMap();
 		}
 	}
-}
\ No newline at end of file
+}
diff --git a/SCANui.cs b/SCANui.cs
index d6b3964..5c27f66 100644
--- a/SCANui.cs
+++ b/SCANui.cs
@@ -975,7 +975,7 @@ private static void drawLegendLabel(Rect r, float val, float min, float max) {
 			drawLabel(lr, Color.white, txt, false, true);
 		}
 
-		private static void drawLegend() {
+		private static Rect drawLegend() {
 			if(bigmap.mapmode == 0 && SCANcontroller.controller.legend) {
 				GUILayout.Label("", GUILayout.ExpandWidth(true));
 				Rect r = GUILayoutUtility.GetLastRect();
@@ -984,7 +984,8 @@ private static void drawLegend() {
 				for(float val=-1000f; val < 9000f; val += 1000f) {
 					drawLegendLabel(r, val, -1500f, 9000f);
 				}
-			}
+				return r;
+			}return new Rect(0,0,0,0);
 		}
 
 		private static void gui_bigmap_build(int wid) {
@@ -1209,17 +1210,27 @@ private static void gui_bigmap_build(int wid) {
 					info += " " + mlat.ToString("F") + " " + mlon.ToString("F"); // uncomment for debugging projections
 				}
 			}
+			
+			Rect legend_rect;
 			if(maprect.width < 720) {
 				GUILayout.EndHorizontal();
 				readableLabel(info, Color.white);
-				drawLegend();
+				legend_rect = drawLegend();
 			} else {
 				GUILayout.BeginVertical();
 				readableLabel(info, Color.white);
-				drawLegend();
+				legend_rect = drawLegend();
 				GUILayout.EndVertical();
 				GUILayout.EndHorizontal();
 			}
+			bool in_gradient_legend = false;
+			float gradient_height = -1;
+			if(legend_rect.width>0f) {
+				float mgx = (Event.current.mousePosition.x - legend_rect.x) / legend_rect.width;
+				float mgy = (Event.current.mousePosition.y - legend_rect.y) / legend_rect.height;
+				in_gradient_legend = (mgx>=0f) && (mgx<=1f) && (mgy>=0f) && (mgy<=1f);
+				gradient_height = -1500f+(mgx*10500f);
+			}
 
 			if(!notMappingToday) drawMapLabels(maprect, vessel, bigmap, data);
 
@@ -1270,6 +1281,12 @@ private static void gui_bigmap_build(int wid) {
 								pos_spotmap.y = Math.Max(maprect.y, Math.Min(maprect.y + maprect.height - pos_spotmap.height, pos_spotmap.y));
 							}
 						}
+						if (in_gradient_legend)
+						{
+							SCANmap.heightGradientRange = gradient_height-SCANmap.startGradientHeight;
+							bigmap.resetMap();
+							if(spotmap != null) spotmap.resetMap();
+						}
 					} else if(Event.current.button == 0) {
 						if(spotmap != null && in_spotmap) {
 							spotmap.mapscale = spotmap.mapscale / 1.25f;
@@ -1277,6 +1294,14 @@ private static void gui_bigmap_build(int wid) {
 							spotmap.resetMap(spotmap.mapmode);
 							Event.current.Use();
 						}
+						if (in_gradient_legend)
+						{
+							float end_pos = SCANmap.startGradientHeight+SCANmap.heightGradientRange;
+							SCANmap.startGradientHeight = gradient_height;
+							SCANmap.heightGradientRange = end_pos-SCANmap.startGradientHeight;
+							bigmap.resetMap();
+							if(spotmap != null) spotmap.resetMap();
+						}
 					}
 					Event.current.Use();
 				} else if(Event.current.type == EventType.MouseDown) {