diff --git a/include/DetectorConstruction.hh b/include/DetectorConstruction.hh
index 0be4e3f..ef5c6e3 100644
--- a/include/DetectorConstruction.hh
+++ b/include/DetectorConstruction.hh
@@ -7,6 +7,7 @@
 
 class G4VPhysicalVolume;
 class G4LogicalVolume;
+class DetectorConstructionMessenger;
 
 /// Detector construction class to define materials and geometry.
 
@@ -19,12 +20,9 @@ class DetectorConstruction : public G4VUserDetectorConstruction
     virtual G4VPhysicalVolume* Construct();
     virtual void ConstructSDandField();
 
-    const G4String GetTargetMaterial() { return fTargetMaterial; }
-    void SetTargetMaterial(const G4String mat) { fTargetMaterial = mat; }
+    void ComputeGeometry();
 
-  protected:
-    // void DefineMaterials();
-    G4bool  fCheckOverlaps;
+    // public fields to avoid all getters and setters
     G4double scSizeX;
     G4double scSizeY;
     G4double scSizeZ;
@@ -47,11 +45,19 @@ class DetectorConstruction : public G4VUserDetectorConstruction
     G4double targetX;
     G4double targetY;
     G4double targetZ;
-    G4String fTargetMaterial;
+    G4double targetLocationX;
+    G4double targetLocationY;
+    G4double targetLocationZ;
+    G4String targetMaterialStr;
 
     G4double worldSizeX;
     G4double worldSizeY;
     G4double worldSizeZ;
+
+  protected:
+    // void DefineMaterials();
+    G4bool fCheckOverlaps;
+    DetectorConstructionMessenger *fDetConMessenger;
 };
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo......
diff --git a/src/DetectorConstruction.cc b/src/DetectorConstruction.cc
index fac507f..d411c47 100644
--- a/src/DetectorConstruction.cc
+++ b/src/DetectorConstruction.cc
@@ -1,5 +1,6 @@
 #include "DetectorConstruction.hh"
 
+#include "DetectorConstructionMessenger.hh"
 #include "G4Box.hh"
 #include "G4LogicalVolume.hh"
 #include "G4MultiFunctionalDetector.hh"
@@ -21,10 +22,11 @@
 
 DetectorConstruction::DetectorConstruction()
     : G4VUserDetectorConstruction(), fCheckOverlaps(true) {
+  fDetConMessenger = new DetectorConstructionMessenger(this);
   // DefineMaterials();
 }
 
-DetectorConstruction::~DetectorConstruction() {}
+DetectorConstruction::~DetectorConstruction() { delete fDetConMessenger; }
 
 G4VPhysicalVolume *DetectorConstruction::Construct() {
   G4NistManager *nist = G4NistManager::Instance();
@@ -34,35 +36,8 @@ G4VPhysicalVolume *DetectorConstruction::Construct() {
   G4Material *scMaterial =
       nist->FindOrBuildMaterial("G4_PLASTIC_SC_VINYLTOLUENE");
 
-  // World and crystals
-  scSizeX = 5.0 * cm;
-  scSizeY = 50.0 * cm;
-  scSizeZ = 1. * cm;
-  scGapX = 0.2 * cm;
-  scGapZ = 0.2 * cm;
-  nScBar = 10;
-  nLayerTop = 2;
-  nLayerBottom = 2;
-
-  layerGapZ = 1 * cm;
-  topBotGap = 50 * cm;
-
-  layerSizeX = nScBar * scSizeX + nScBar * scGapX;
-  layerSizeY = nScBar * scSizeX + nScBar * scGapX;
-  layerSizeZ = scSizeZ + scGapZ;
-
-  concreteX = 30 * cm;
-  concreteY = 30 * cm;
-  concreteZ = 30 * cm;
-  targetX = 10 * cm;
-  targetY = 10 * cm;
-  targetZ = 5 * cm;
-
-  worldSizeX = 1.2 * layerSizeX;
-  worldSizeY = 1.2 * layerSizeY;
-  worldSizeZ =
-      1.2 * ((nLayerBottom + nLayerTop) * (layerSizeZ + layerGapZ) + topBotGap);
-
+  // ComputeGeometry first
+  ComputeGeometry();
   // world volume
   G4Box *solidWorld =
       new G4Box("World", 0.5 * worldSizeX, 0.5 * worldSizeY, 0.5 * worldSizeZ);
@@ -90,8 +65,9 @@ G4VPhysicalVolume *DetectorConstruction::Construct() {
       new G4Box("target", targetX / 2, targetY / 2, targetZ / 2);
   G4LogicalVolume *logTarget =
       new G4LogicalVolume(solidTarget, targetMaterial, "target");
-  new G4PVPlacement(0, G4ThreeVector(), logTarget, "target", logConcrete, false,
-                    0, fCheckOverlaps);
+  new G4PVPlacement(
+      0, G4ThreeVector(targetLocationX, targetLocationY, targetLocationZ),
+      logTarget, "target", logConcrete, false, 0, fCheckOverlaps);
 
   // scintillators
   G4Box *solidScX =
@@ -177,3 +153,33 @@ void DetectorConstruction::ConstructSDandField() {
   mfDetY->RegisterPrimitive(primitiv2);
   SetSensitiveDetector("logicScY", mfDetY);
 }
+
+void DetectorConstruction::ComputeGeometry() {
+  scSizeX = 5.0 * cm;
+  scSizeY = 50.0 * cm;
+  scSizeZ = 1. * cm;
+  scGapX = 0.2 * cm;
+  scGapZ = 0.2 * cm;
+  nScBar = 10;
+  nLayerTop = 2;
+  nLayerBottom = 2;
+
+  layerGapZ = 1 * cm;
+  topBotGap = 50 * cm;
+
+  layerSizeX = nScBar * scSizeX + nScBar * scGapX;
+  layerSizeY = nScBar * scSizeX + nScBar * scGapX;
+  layerSizeZ = scSizeZ + scGapZ;
+
+  concreteX = 30 * cm;
+  concreteY = 30 * cm;
+  concreteZ = 30 * cm;
+  targetX = 10 * cm;
+  targetY = 10 * cm;
+  targetZ = 5 * cm;
+
+  worldSizeX = 1.2 * layerSizeX;
+  worldSizeY = 1.2 * layerSizeY;
+  worldSizeZ =
+      1.2 * ((nLayerBottom + nLayerTop) * (layerSizeZ + layerGapZ) + topBotGap);
+}
diff --git a/src/DetectorConstructionMessenger.cc b/src/DetectorConstructionMessenger.cc
index 8657474..593809f 100644
--- a/src/DetectorConstructionMessenger.cc
+++ b/src/DetectorConstructionMessenger.cc
@@ -17,18 +17,25 @@ DetectorConstructionMessenger::DetectorConstructionMessenger(
   fMuTomoDirectory = new G4UIdirectory("/muTomo/");
   fMuTomoDirectory->SetGuidance("Customize muon tomography geometry commands.");
 
-  fTargetMaterialCmd =
-      new G4UIcmdWithAString("/muTomo/setTargetMaterial", this);
+  fTargetMaterialCmd = new G4UIcmdWithAString("/muTomo/targetMaterial", this);
   fTargetMaterialCmd->SetGuidance("Set target material.");
   fTargetMaterialCmd->SetParameterName("targetMaterial", true);
   fTargetMaterialCmd->SetDefaultValue("G4_Pb");
 
-  fTargetSizeCmd = new G4UIcmdWith3VectorAndUnit("/muTomo/setTargetSize", this);
+  fTargetSizeCmd = new G4UIcmdWith3VectorAndUnit("/muTomo/targetSize", this);
   fTargetSizeCmd->SetGuidance("Set target size.");
-  fTargetSizeCmd->SetParameterName("muTomoSizeX", "muTomoSizeY", "muTomoSizeZ",
+  fTargetSizeCmd->SetParameterName("targetSizeX", "targetSizeY", "targetSizeZ",
                                    true);
   fTargetSizeCmd->SetDefaultValue(G4ThreeVector(6., 2., 6.));
   fTargetSizeCmd->SetDefaultUnit("mm");
+
+  fTargetLocationCmd =
+      new G4UIcmdWith3VectorAndUnit("/muTomo/targetLocation", this);
+  fTargetLocationCmd->SetGuidance("Set target location.");
+  fTargetLocationCmd->SetParameterName("targetLocationX", "targetLocationY",
+                                       "targetLocationZ", true);
+  fTargetLocationCmd->SetDefaultValue(G4ThreeVector(0., 0., 0.));
+  fTargetLocationCmd->SetDefaultUnit("mm");
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
@@ -36,18 +43,28 @@ DetectorConstructionMessenger::DetectorConstructionMessenger(
 DetectorConstructionMessenger::~DetectorConstructionMessenger() {
   delete fTargetMaterialCmd;
   delete fTargetSizeCmd;
+  delete fTargetLocationCmd;
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
 
 void DetectorConstructionMessenger::SetNewValue(G4UIcommand *command,
                                                 G4String newValue) {
-  // if (command == fTargetMaterialCmd) {
-  // fDetCon->SetMaterial(newValue);
-  // }
-  // if (command == fTargetSizeCmd) {
-  // fDetCon->SetSizes(fTargetSizeCmd->GetNew3VectorValue(newValue));
-  // }
+  if (command == fTargetMaterialCmd) {
+    fDetCon->targetMaterialStr = newValue;
+  }
+  if (command == fTargetSizeCmd) {
+    G4ThreeVector newPos = fTargetSizeCmd->GetNew3VectorValue(newValue);
+    fDetCon->targetX = newPos.x();
+    fDetCon->targetY = newPos.y();
+    fDetCon->targetZ = newPos.z();
+  }
+  if (command == fTargetLocationCmd) {
+    G4ThreeVector newLoc = fTargetLocationCmd->GetNew3VectorValue(newValue);
+    fDetCon->targetLocationX = newLoc.x();
+    fDetCon->targetLocationY = newLoc.y();
+    fDetCon->targetLocationZ = newLoc.z();
+  }
 }
 
 //....oooOO0OOooo........oooOO0OOooo........oooOO0OOooo........oooOO0OOooo....
@@ -55,12 +72,19 @@ void DetectorConstructionMessenger::SetNewValue(G4UIcommand *command,
 G4String DetectorConstructionMessenger::GetCurrentValue(G4UIcommand *command) {
   G4String cv;
 
-  // if (command == fTargetMaterialCmd) {
-  // cv = fDetCon->GetMaterial();
-  // }
-  // if (command == fTargetSizeCmd) {
-  // cv = fTargetSizeCmd->ConvertToString(fDetCon->GetSizes(), "mm");
-  // }
+  if (command == fTargetMaterialCmd) {
+    cv = fDetCon->targetMaterialStr;
+  }
+  if (command == fTargetSizeCmd) {
+    cv = fTargetSizeCmd->ConvertToString(
+        G4ThreeVector(fDetCon->targetX, fDetCon->targetY, fDetCon->targetZ));
+  }
+  if (command == fTargetLocationCmd) {
+    cv = fTargetLocationCmd->ConvertToString(
+        G4ThreeVector(fDetCon->targetLocationX, fDetCon->targetLocationY,
+                      fDetCon->targetLocationZ));
+  }
+
   return cv;
 }