diff --git a/src/Geodesy/Distance/BaseDistance.php b/src/Geodesy/Distance/BaseDistance.php
index 0335fe0..5557c13 100644
--- a/src/Geodesy/Distance/BaseDistance.php
+++ b/src/Geodesy/Distance/BaseDistance.php
@@ -5,6 +5,8 @@
 use Geodesy\Location\LatLong;
 use Geodesy\Unit\UnitInterface;
 use Geodesy\Unit\Metre;
+use Geodesy\Unit\Mile;
+use Geodesy\Unit\KiloMetre;
 
 abstract class BaseDistance
 {
@@ -22,7 +24,7 @@ public function __construct(LatLong $source, LatLong $destination)
         $this->source = $source;
         $this->destination = $destination;
         $this->radius = self::R;
-        $this->unit = null;
+        $this->unit = new KiloMetre;
     }
 
     public function setUnit(UnitInterface $unit)
@@ -37,22 +39,14 @@ public function getUnit()
 
     public function getDistance()
     {
-        $dist = $this->distance();
-        if($this->getUnit() instanceof Metre){
-            $dist = $dist * 1000;
-         }
-        $this->unit->setValue($dist);
-        return $this->unit->getValue();
+        return $this->getUnit()->convert($this->distance());
     }
 
     abstract public function distance();
 
     public function isInRange($range)
     {
-        if($this->getUnit() instanceof Metre){
-            $range = $range * 1000;
-         }
-        return $this->getDistance() <= $range;
+        return $this->getDistance() <= $this->getUnit()->convert($range);
     }
 
 }
\ No newline at end of file
diff --git a/src/Geodesy/Distance/HaversineFormula.php b/src/Geodesy/Distance/HaversineFormula.php
index 1a93868..e6f6f01 100644
--- a/src/Geodesy/Distance/HaversineFormula.php
+++ b/src/Geodesy/Distance/HaversineFormula.php
@@ -3,9 +3,6 @@
 namespace Geodesy\Distance;
 
 use Geodesy\Location\LatLong;
-use Geodesy\Unit\KiloMetre;
-use Geodesy\Unit\Metre;
-
 
 class HaversineFormula extends BaseDistance implements DistanceInterface
 {
@@ -14,7 +11,6 @@ class HaversineFormula extends BaseDistance implements DistanceInterface
     public function __construct(LatLong $source, LatLong $destination)
     {
         parent::__construct($source, $destination);
-        $this->unit = new Kilometre;
     }
 
     /**
diff --git a/src/Geodesy/Distance/SphericalCosine.php b/src/Geodesy/Distance/SphericalCosine.php
index 519a263..a3b8c0b 100644
--- a/src/Geodesy/Distance/SphericalCosine.php
+++ b/src/Geodesy/Distance/SphericalCosine.php
@@ -3,8 +3,6 @@
 namespace Geodesy\Distance;
 
 use Geodesy\Location\LatLong;
-use Geodesy\Unit\KiloMetre;
-use Geodesy\Unit\Metre;
 
 class SphericalCosine extends BaseDistance implements DistanceInterface
 {
@@ -12,7 +10,6 @@ class SphericalCosine extends BaseDistance implements DistanceInterface
     public function __construct(LatLong $source, LatLong $destination)
     {
         parent::__construct($source, $destination);
-        $this->unit = new Kilometre;
     }
 
     /**
diff --git a/src/Geodesy/Distance/VincentyFormula.php b/src/Geodesy/Distance/VincentyFormula.php
index e1fc1bc..19de488 100644
--- a/src/Geodesy/Distance/VincentyFormula.php
+++ b/src/Geodesy/Distance/VincentyFormula.php
@@ -3,8 +3,6 @@
 namespace Geodesy\Distance;
 
 use Geodesy\Location\LatLong;
-use Geodesy\Unit\Metre;
-use Geodesy\Unit\KiloMetre;
 
 class VincentyFormula extends BaseDistance implements DistanceInterface
 {
@@ -12,7 +10,6 @@ class VincentyFormula extends BaseDistance implements DistanceInterface
     public function __construct(LatLong $source, LatLong $destination)
     {
         parent::__construct($source, $destination);
-        $this->unit = new KiloMetre;
     }
 
     /**
diff --git a/src/Geodesy/Unit/BaseUnit.php b/src/Geodesy/Unit/BaseUnit.php
index f71d286..56aa56a 100644
--- a/src/Geodesy/Unit/BaseUnit.php
+++ b/src/Geodesy/Unit/BaseUnit.php
@@ -3,25 +3,9 @@
 namespace Geodesy\Unit;
 
 
-class BaseUnit
+abstract class BaseUnit
 {
 
-    protected $value;
-
-    public function __construct()
-    {
-        $this->value = null;
-    }
-
-    public function setValue($value)
-    {
-        $this->value = $value;
-    }
-
-    public function getValue()
-    {
-        return $this->value;
-    }
-
+    abstract public function convert($value);
 
 }
\ No newline at end of file
diff --git a/src/Geodesy/Unit/KiloMetre.php b/src/Geodesy/Unit/KiloMetre.php
index 28e9ea2..65c17bb 100644
--- a/src/Geodesy/Unit/KiloMetre.php
+++ b/src/Geodesy/Unit/KiloMetre.php
@@ -6,5 +6,10 @@
 class KiloMetre extends BaseUnit implements UnitInterface
 {
 
+	// This is our base unit, so just return it
+    public function convert($value)
+    {
+        return $value;
+    }
 
 }
\ No newline at end of file
diff --git a/src/Geodesy/Unit/Metre.php b/src/Geodesy/Unit/Metre.php
index 73242b7..38c0463 100644
--- a/src/Geodesy/Unit/Metre.php
+++ b/src/Geodesy/Unit/Metre.php
@@ -6,5 +6,9 @@
 class Metre extends BaseUnit implements UnitInterface
 {
 
+    public function convert($value)
+    {
+        return $value * 1000;
+    }
 
 }
\ No newline at end of file
diff --git a/src/Geodesy/Unit/Mile.php b/src/Geodesy/Unit/Mile.php
new file mode 100644
index 0000000..8cd7edb
--- /dev/null
+++ b/src/Geodesy/Unit/Mile.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace Geodesy\Unit;
+
+
+class Mile extends BaseUnit implements UnitInterface
+{
+
+    public function convert($value)
+    {
+        return $value * 0.62137;
+    }
+
+}
\ No newline at end of file
diff --git a/src/Geodesy/Unit/NauticalMile.php b/src/Geodesy/Unit/NauticalMile.php
new file mode 100644
index 0000000..f25b1b6
--- /dev/null
+++ b/src/Geodesy/Unit/NauticalMile.php
@@ -0,0 +1,14 @@
+<?php
+
+namespace Geodesy\Unit;
+
+
+class NauticalMile extends BaseUnit implements UnitInterface
+{
+
+    public function convert($value)
+    {
+        return $value * 0.539957;
+    }
+
+}
\ No newline at end of file