diff --git a/Source/Particles/TracerPC.cpp b/Source/Particles/TracerPC.cpp
index dc788e70..3fa12c86 100644
--- a/Source/Particles/TracerPC.cpp
+++ b/Source/Particles/TracerPC.cpp
@@ -161,8 +161,10 @@ TracerPC::AdvectWithUmac (Array<MultiFab const*, AMREX_SPACEDIM> umac,
                     iv[1] += domain.smallEnd()[1];
                     ParticleReal zlo, zhi;
                     if (use_terrain) {
-                        zlo = zheight(iv[0], iv[1], iv[2]);
-                        zhi = zheight(iv[0], iv[1], iv[2]+1);
+                        zlo = Real(0.25) * (zheight(iv[0],iv[1]  ,iv[2]  ) + zheight(iv[0]+1,iv[1]  ,iv[2]  ) +
+                                            zheight(iv[0],iv[1]+1,iv[2]  ) + zheight(iv[0]+1,iv[1]+1,iv[2]  ));
+                        zhi = Real(0.25) * (zheight(iv[0],iv[1]  ,iv[2]+1) + zheight(iv[0]+1,iv[1]  ,iv[2]+1) +
+                                            zheight(iv[0],iv[1]+1,iv[2]+1) + zheight(iv[0]+1,iv[1]+1,iv[2]+1));
                     } else {
                         zlo =  iv[2]    * dx[2];
                         zhi = (iv[2]+1) * dx[2];