diff --git a/OpenSim/Framework/Constants.cs b/OpenSim/Framework/Constants.cs
index b2871ec36c..63ce43081b 100644
--- a/OpenSim/Framework/Constants.cs
+++ b/OpenSim/Framework/Constants.cs
@@ -43,9 +43,15 @@ namespace OpenSim.Framework
         public const uint MaximumRegionSize = 4096;
 
         // Since terrain is stored in 16x16 heights, regions must be a multiple of this number and that is the minimum
-        public const int MinRegionSize = 16;
+        // but for placement on a grid min must be 256m
+        public const int MinRegionSize = 256;
         public const int TerrainPatchSize = 16;
 
+        public const float MinSimulationHeight = -100f;
+        public const float MaxSimulationHeight = 50000f;
+        public const float MinTerrainHeightmap = -100f;
+        public const float MaxTerrainHeightmap = 4000f;
+
         public const string DefaultTexture = "89556747-24cb-43ed-920b-47caed15465f";
 
         public static readonly UUID m_MrOpenSimID = new UUID("11111111-1111-0000-0000-000100bba000");
diff --git a/OpenSim/Region/PhysicsModules/ubOde/ODECharacter.cs b/OpenSim/Region/PhysicsModules/ubOde/ODECharacter.cs
index 52bae97a70..245fbd14df 100644
--- a/OpenSim/Region/PhysicsModules/ubOde/ODECharacter.cs
+++ b/OpenSim/Region/PhysicsModules/ubOde/ODECharacter.cs
@@ -177,11 +177,11 @@ namespace OpenSim.Region.PhysicsModule.ubOde
 
             if(pos.IsFinite())
             {
-                if(pos.Z > 99999f)
+                if(pos.Z > Constants.MaxSimulationHeight)
                 {
                     pos.Z = parent_scene.GetTerrainHeightAtXY(127,127) + 5;
                 }
-                if(pos.Z < -100f) // shouldn't this be 0 ?
+                if(pos.Z < Constants.MinSimulationHeight) // shouldn't this be 0 ?
                 {
                     pos.Z = parent_scene.GetTerrainHeightAtXY(127,127) + 5;
                 }
diff --git a/OpenSim/Region/PhysicsModules/ubOde/ODEPrim.cs b/OpenSim/Region/PhysicsModules/ubOde/ODEPrim.cs
index 842bc0b544..121a8ce937 100644
--- a/OpenSim/Region/PhysicsModules/ubOde/ODEPrim.cs
+++ b/OpenSim/Region/PhysicsModules/ubOde/ODEPrim.cs
@@ -987,7 +987,7 @@ namespace OpenSim.Region.PhysicsModule.ubOde
                 {
                     _position.X = Util.Clip(_position.X, 0.5f, _parent_scene.WorldExtents.X - 0.5f);
                     _position.Y = Util.Clip(_position.Y, 0.5f, _parent_scene.WorldExtents.Y - 0.5f);
-                    _position.Z = Util.Clip(_position.Z + 0.2f, -100f, 50000f);
+                    _position.Z = Util.Clip(_position.Z + 0.2f, Constants.MinSimulationHeight, Constants.MaxSimulationHeight);
 
                     m_lastposition = _position;
                     _velocity.X = 0;
diff --git a/OpenSim/Region/PhysicsModules/ubOde/ODEScene.cs b/OpenSim/Region/PhysicsModules/ubOde/ODEScene.cs
index dc65a2cc72..fa1fd564b7 100644
--- a/OpenSim/Region/PhysicsModules/ubOde/ODEScene.cs
+++ b/OpenSim/Region/PhysicsModules/ubOde/ODEScene.cs
@@ -2068,9 +2068,7 @@ namespace OpenSim.Region.PhysicsModule.ubOde
                         if (x > 1 && x < maxXX)
                             xx++;
 
-                        val = heightMap[yy + xx];
-                        if (val < -100.0f)
-                            val = -100.0f;
+                        val = Util.Clamp(heightMap[yy + xx], Constants.MinTerrainHeightmap, Constants.MaxTerrainHeightmap);
                         if(val > maxH)
                             maxH = val;
                         if(val < minH)