Use BigDecimal to store player position.

src/minecraft/net/minecraft/src/EntityPlayer.java

@@ -1020,6 +1020,11 @@ public abstract class EntityPlayer extends EntityLiving implements ICommandSende
         this.experience = par1NBTTagCompound.getFloat("XpP");
         this.experienceLevel = par1NBTTagCompound.getInteger("XpLevel");
         this.experienceTotal = par1NBTTagCompound.getInteger("XpTotal");
+        if(par1NBTTagCompound.hasKey("PosXBig")) {
+        	this.posXBig = par1NBTTagCompound.getBigDecimal("PosXBig");
+            this.posXBig = par1NBTTagCompound.getBigDecimal("PosXBig");
+            setPosition(posXBig, posY, posZBig);
+        }
 
         if (this.sleeping)
         {
@@ -1055,6 +1060,8 @@ public abstract class EntityPlayer extends EntityLiving implements ICommandSende
         par1NBTTagCompound.setFloat("XpP", this.experience);
         par1NBTTagCompound.setInteger("XpLevel", this.experienceLevel);
         par1NBTTagCompound.setInteger("XpTotal", this.experienceTotal);
+        par1NBTTagCompound.setBigDecimal("PosXBig", posXBig);
+        par1NBTTagCompound.setBigDecimal("PosZBig", posZBig);
 
         if (this.spawnChunk != null)
         {

src/minecraft/net/minecraft/src/NBTTagCompound.java

@@ -3,6 +3,8 @@ package net.minecraft.src;
 import java.io.DataInput;
 import java.io.DataOutput;
 import java.io.IOException;
+import java.math.BigDecimal;
+
 import org.mcmodule.math.BigInteger;
 import java.util.Collection;
 import java.util.HashMap;
@@ -326,8 +328,17 @@ public class NBTTagCompound extends NBTBase
 		if(value == null) value = BigInteger.ZERO;
 		setString(key, value.toString());	
 	}
+	
+	public void setBigDecimal(String key, BigDecimal value) {
+		if(value == null) value = BigDecimal.ZERO;
+		setString(key, value.toString());	
+	}
 
 	public BigInteger getBigInteger(String key) {
 		return new BigInteger(getString(key));
 	}
+
+	public BigDecimal getBigDecimal(String key) {
+		return new BigDecimal(getString(key));
+	}
 }

src/minecraft/net/minecraft/src/ServerConfigurationManager.java

@@ -74,7 +74,7 @@ public abstract class ServerConfigurationManager
         this.sendTimeAndRainingToPlayer(par2EntityPlayerMP, var4);
         this.sendPacketToAllPlayers(new Packet3Chat("\u00a7e" + par2EntityPlayerMP.username + " joined the game."));
         this.func_72377_c(par2EntityPlayerMP);
-        var6.setPlayerLocation(par2EntityPlayerMP.posX, par2EntityPlayerMP.posY, par2EntityPlayerMP.posZ, par2EntityPlayerMP.rotationYaw, par2EntityPlayerMP.rotationPitch);
+        var6.setPlayerLocation(par2EntityPlayerMP.posXBig, par2EntityPlayerMP.posY, par2EntityPlayerMP.posZBig, par2EntityPlayerMP.rotationYaw, par2EntityPlayerMP.rotationPitch);
         this.mcServer.getNetworkThread().func_71745_a(var6);
         var6.sendPacketToPlayer(new Packet4UpdateTime(var4.getWorldTime()));