diff --git a/OpenSim/Framework/TerrainData.cs b/OpenSim/Framework/TerrainData.cs
index 30d1a13298..7b4905ac2b 100644
--- a/OpenSim/Framework/TerrainData.cs
+++ b/OpenSim/Framework/TerrainData.cs
@@ -518,8 +518,8 @@ namespace OpenSim.Framework
                         for (int yy = 0; yy < SizeY; yy++)
                             for (int xx = 0; xx < SizeX; xx++)
                             {
-                                // reduce to 1cm resolution
-                                float val = (float)Math.Round(m_heightmap[xx, yy],2,MidpointRounding.ToEven);
+                                // reduce to 1mm resolution
+                                float val = (float)Math.Round(m_heightmap[xx, yy],3,MidpointRounding.AwayFromZero);
                                 bw.Write(val);
                             }
                     }
diff --git a/prebuild48.xml b/prebuild48.xml
index 8d9b66ee9e..876a6b1c3e 100644
--- a/prebuild48.xml
+++ b/prebuild48.xml
@@ -3,7 +3,7 @@
   <Solution activeConfig="Debug" name="OpenSim" path="./" version="0.5.0-$Rev$">
     <Configuration name="Debug" >
       <Options>
-        <CompilerDefines>TRACE;DEBUG</CompilerDefines>
+        <CompilerDefines>TRACE;DEBUG;NET48</CompilerDefines>
         <OptimizeCode>false</OptimizeCode>
         <CheckUnderflowOverflow>false</CheckUnderflowOverflow>
         <AllowUnsafe>true</AllowUnsafe>
@@ -19,7 +19,7 @@
     </Configuration>
     <Configuration name="Release">
       <Options>
-        <CompilerDefines>TRACE</CompilerDefines>
+        <CompilerDefines>TRACE;NET48</CompilerDefines>
         <OptimizeCode>true</OptimizeCode>
         <CheckUnderflowOverflow>false</CheckUnderflowOverflow>
         <AllowUnsafe>true</AllowUnsafe>